Copying files in linux

Lately I've been doing a lot of embedded development with Linux, and copying files between systems has been a bit of a pain. Fortunately, a combination of RSync and SSH solved my problems, with a command that lets me copy files from a directory on one system to a directory on another system, recursively with symlink preservation (and even duplication !) :

rsync -azuv -e ssh  user@systemaddress:~/path/to/dir/* .

WTF ?! Windows (as of Vista) no longer supports multiple different monitors!? WHY ????

Apparently, as of Windows Vista and later, Windows no longer supports multiple video cards that don't use the same driver!! Why ? I use a Radeon and a Matrox QID to drive 6 displays on my development box, and this just entirely fucks me over. At best, I can only use four of my displays now, and that's only going to be when Matrox gets off their lazy ass and releases a Windows 7 driver for their QID LP PCIe video cards. I'm so disappointed with what's a complete step backward for Microsoft. Epic fail, Microsoft.

Seeing where Perl looks for its modules on a system

Because we have very limited space on some embedded devices that we use that run Perl, we can only store a very few modules on these systems. This is a consequence of the fact that we run Busybox on these things, so by definition everything on these boxes is limited, if present at all. Therefore, we have to check and see if a module is available before we can use it in our code. Fortunately, there's a quick one-liner to see where Perl is looking for modules on a system :

perl -e'print join "\n", @INC'

I got this off a forum post from somewhere, and I'd post it here if I could find the link again. My apologies to the author of that forum post if they ever happen to run across this blog.

Embarking on a Perl journey

A long time ago, in a job far, far away, I had to deal with some Perl. I learned just enough to get me by for the duration of the task at hand, and then pretty much forgot everything I had learned. Now, at my latest job, I'm having to deal extensively with legacy systems which have a considerable amount of logic written in Perl that needs to be either ported over to other languages (for various reasons) or updated and new things written because Perl is the only language that's both abstract enough and not too processor intensive to run on the embedded systems we deal with. Therefore, you're going to start seeing a lot more Perl posts on this blog.

Setting up Tomcat (5.5) on Ubuntu Server 8.10

I recently ran into some old quirks when provisioning a new server for our company's web applications on Ubuntu 8.10 (Intrepid Ibex). Because the manager apps are no longer installed by default, you need to add extra packages to the list to install when installing Tomcat :

sudo apt-get install -y tomcat5.5 tomcat5.5-admin tomcat5.5-webapps

If you're copying configuration over from a previous Tomcat / Ubuntu installation, you need to make sure the permissions on all the files you copy are set correctly. In most cases, you'll have to run :

chown -R tomcat55:adm [file and folder list here]

If you're securing the applications with a certificate, try to make sure it's valid for your location and ensure that you've set it properly in your server.xml configuration file. If you want useful logging, you'll also have to place a log4j.properties file in

$CATALINA_HOME/common/classes

Hope this helps.

Dumping just your schema with MySQL dump

A simple one-liner :

mysqldump -u root -p mydatabasename --no-data=true --add-drop-table=false > test_dump.sql

With this command, you'll be prompted for your root password. I got this from here. Simple

The Curious Case of Damned DataIntegrityViolationException

In one of the projects on which I contract, we recently started encountering a problem importing and parsing text record files into our system which previously had no problem. My first thought on hearing this was that the partner from which we obtain the files had changed the file format (again). Upon closer inspection, nothing had changed in the files. My next step was to try importing them into a development system and seeing what was going on. As it turned out, the application was catching Spring's DataIntegrityViolationException. I was floored as soon as I saw this because our application was supposed to be catching this exception behind one of the business interfaces and converting it to an internal exception which is used in business logic. After some more poking around to confirm what was really going on, I threw the problem into google, and on the second result was a post in the Spring forum made by a user having exactly the same problem I was.


To summarize their problem quickly, they were using a transaction manager, and they were intercepting their business methods (via interfaces) with Aspects, which we're also doing. The problem was this : as soon as the internal Aspects were applied to the business interface, this changed the ordering of advice applied to the interface implementor, so now the Hibernate session underneath was getting flushed later by the transaction manager, instead of in the business method where it had been flushed previously. The result of this was that now DataIntegrityViolationExceptions were being thrown outside of the interecepted method, instead of inside where it was expected. A manual session.flush() inside of a HibernateCallback within the business method fixed this :

 /**
  * @see AchPaymentNoticeOfChangeService#registerNoc(AchPaymentNoticeOfChange)
  */
 @Override
 public void registerNoc(final AchPaymentNoticeOfChange changeNotification) throws IllegalArgumentException, NoticeOfChangeAlreadyExistsException, Exception {
  try {
   getHibernateTemplate().execute(new HibernateCallback() {
    @Override
    public Object doInHibernate(Session session) throws HibernateException, SQLException {
     
     session.save (changeNotification);
     
     // flush the session to ensure that the database gets synchronized
     // the end of this call, rather than waiting for any transaction
     // managers to handle it and risk letting a DataIntegrityViolationException
     // occur outside of this method's handling
     session.flush();
     
     return null;
    }
   });
  } catch (DataIntegrityViolationException dive) {
   throw new NoticeOfChangeAlreadyExistsException("A notice of change already exists for payment ["+changeNotification.getAchPayment().getId()+"]", dive, changeNotification);
  } catch (Exception e) {
   throw e;
  }
 }

I hope this post finds somebody else who runs into this problem.

Composing XML in C# 2.0 or later

When testing some custom XML serialization I was writing for a project, I ran across a quirk of the XmlWriter created by XmlWriter#Create() : The writer that gets produced by this method doesn't actually write out XML to whatever stream or file you've given it in the Create method until Close() is called on the generated writer. This means that if you've been using the XmlWriter along with a using() statement, you're fine, but if you haven't been using it, as I have in the unit tests I've been trying to write, you're going to get some unexpected results. Something to pay attention to.

Visual Studio (2010?) Debugging Gotchas - Part I

I recently ran across a problem where I was trying to debug some code and the Visual Studio debugger wouldn't stop in my class. It would stop in the test class from which I was debugging, but not the class I really wanted to debug. I looked on the breakpoint and noticed that it was transparent, so I hovered over it to view the tooltip, and the tooltip informed me that my class had a DebuggerStepThroughAttribute assigned to it. My first thought was "what ? that's bullshit", and then it occurred to me that I hadn't looked at the rest of the (partial) class which was defined in another file that was generated from an XML schema by xsd.exe. Sure enough, xsd.exe places DebuggerStepThroughAttribute attributes on the classes it generates. Why is this default behaviour ? This was an annoying as hell bug that took time out of my day that's better devoted to other things, like being productive so that I don't get shit from my boss. It also took more time than I'd care to admit to, largely due to my inexperience with Visual Studio and .NET. I've had yet to see anything like this coming from a Java / scripting background.

Tricky styling issues in WPF

For about the last 8 or 9 hours (spread across two days) I've been troubleshooting a styling issue in WPF. I have a list of items that I'm displaying in a ListBox that have an 'enabled' property, which is an enum with values OFF and ON. Understand that this type was generated from an XML schema which is very tightly controlled, hence why the type is not a boolean (as would make sense with a name like 'enabled'). I've been trying to create a DataTemplate for the ListBoxItems so that they'll each have an icon associated with them depending on whether they're enabled or not. My original list looked like this :

<ListBox x:Name="ProcedureList" ItemsSource="{Binding Path=procedure}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
  <ListBox.Resources>
    <Style TargetType="{x:Type ListBoxItem}">
      <EventSetter Event="MouseDoubleClick" Handler="WeldProcedure_MouseDoubleClick" />
      <Setter Property="HorizontalContentAlignment" Value="Stretch" />
    </Style>
    <Style TargetType="{x:Type Image}">
      <Style.Triggers>
        <DataTrigger Binding="{Binding}" Value="OFF">
          <Setter Property="Image.Source" Value="Resources/Error_16x16_72.png"/>
        </DataTrigger>
        <DataTrigger Binding="{Binding}" Value="ON">
          <Setter Property="Image.Source" Value="Resources/Success_16x16_72.png"/>
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </ListBox.Resources>
  <ListBox.ItemTemplate>
    <DataTemplate DataType="{x:Type model:WeldingProcedure}">
      <DockPanel HorizontalAlignment="Stretch" LastChildFill="True">
        <Image DockPanel.Dock="Right" Height="16" Width="16" DataContext="{Binding Path=enabled}" ToolTip="Disabled"/>
        <TextBlock DockPanel.Dock="Left" VerticalAlignment="Center" TextAlignment="Left" Text="{Binding Path=procedureName}"/>
      </DockPanel>
    </DataTemplate>
  </ListBox.ItemTemplate>
</ListBox>

However, the images in the DataTemplate were not getting styled with the images as they should have been. As it turns out, if you're referencing default styles in Templates as above, the style resolution doesn't go outside of the template, so the default styling for all Image elements as above needs to go *inside* the DataTemplate resources :

<ListBox x:Name="ProcedureList" ItemsSource="{Binding Path=procedure}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
  <ListBox.Resources>
    <Style TargetType="{x:Type ListBoxItem}">
      <EventSetter Event="MouseDoubleClick" Handler="WeldProcedure_MouseDoubleClick" />
      <Setter Property="HorizontalContentAlignment" Value="Stretch" />
    </Style>
  </ListBox.Resources>
  <ListBox.ItemTemplate>
    <DataTemplate DataType="{x:Type model:WeldingProcedure}">
      <DataTemplate.Resources>
        <Style TargetType="{x:Type Image}">
          <Style.Triggers>
            <DataTrigger Binding="{Binding}" Value="OFF">
              <Setter Property="Image.Source" Value="Resources/Error_16x16_72.png"/>
            </DataTrigger>
            <DataTrigger Binding="{Binding}" Value="ON">
              <Setter Property="Image.Source" Value="Resources/Success_16x16_72.png"/>
            </DataTrigger>
          </Style.Triggers>
        </Style>
      </DataTemplate.Resources>
      <DockPanel HorizontalAlignment="Stretch" LastChildFill="True">
        <Image DockPanel.Dock="Right" Height="16" Width="16" DataContext="{Binding Path=enabled}" ToolTip="Disabled"/>
        <TextBlock DockPanel.Dock="Left" VerticalAlignment="Center" TextAlignment="Left" Text="{Binding Path=procedureName}"/>
      </DockPanel>
    </DataTemplate>
  </ListBox.ItemTemplate>
</ListBox>

Generating XML objects from a schema in .NET

In my last job, I frequently made use of the JAXB library provided with the Java SDK for object de/serialization. I chose to generate my schemata from objects back then because I started off with the business objects and I knew how I wanted to serialize them to XML. Now I have the reverse situation, and I'm using a new language. As it turns out, generating classes from XML schema is dead easy : use the xsd.exe tool. It comes with .NET.

Useful GIMP tricks - Batch file conversion

Now that I've started having to do a lot more documenting for my job, I've found myself importing a lot of pictures taken as steps in tutorials and for providing figures. Since the camera gives us a nice, high-res version that's not really suitable for documentation, I have to scale the images down so that they're in a nice, readable size. When your tutorial has 30 steps, and an image (or even two or three) is required for *each step*, this can mean a lot of manual clicking, dragging, opening and saving in an image editor. Fortunately, GIMP has a plugin called Davids Batch Processor that allows you to easily do fairly simple transforms to file and output them in the format (that's most likely) of your choice. For the simple tasks of rotating, resizing (scaling) and exporting the images in a new format, this plugin's great. There's a tutorial on the site and the plugin itself has already proven to be exceedingly useful for me. I hope it will be for you too.

Subtleties of Perl - Reading files

I've recently begun a new job, and with it has come a whole new segment of the software development universe. The new job uses a lot of Perl, C, Bash and various other languages to get stuff done. Today, I ran afoul of a Perl idiosyncrasy that's worth making a note of, because I'm sure I'll stumble across this problem again and I'm going to need to refer to this in the future. I should also note that I'm writing this as I'm waiting for a significantly large file to parse.

We have large log files that we parse on a daily basis to extract summary information from them about mechanical systems. We read the files, and then output a summary on a secondly basis, one line at a time. Recently, I ran afoul of Perl's file reading mechanisms. When reading files in Perl, there's any number of ways to do so, and it turns out that for the longest time, we've been using the wrong one. Previously, we had been using :

foreach my $line_of_log (<LOG>)
{
    // DO STUFF WITH $line_of_log
}

We thought that this was reading the file in one line of the log file at a time, processing it, and then moving on. What it was actually doing was reading (or "slurping") the whole file into memory, and giving us an array of strings, which we processed one line at a time. After 10 minutes of cursory Googling, I ran across a tutorial which presented this :

while (<LOG>)
{
    my $line_of_log = $_;
    // DO STUFF WITH $line_of_log
}

The 'while' version of the file read actually does what we thought we where doing all along: reading one line from the file, and then doing stuff with it. The difference between the two methods is that in the 'foreach' version, the entire input file gets read into memory, whereas in the 'while' version, only a single line gets read into memory at any given time. As it turns out, another difference is that reading in a 7 MB file resulted in Perl grabbing 34 MB of memory with the 'foreach' version, but only 2.2 MB with the 'while' version. That's an ENTIRE ORDER OF MAGNITUDE in difference!. This also makes a huge difference when running Perl on memory-limited systems, as we are.

Tweaking visual studio

I've recently begun using Visual Studio 2010 Beta 2 more and more as I have increasing amounts of work that require .NET. In order to keep things nicely tabbed the both I and my boss like it, there's a setting that can be set according to instructions founds here : http://mhinze.com/tabs-whitespace-visual-studio/

Using the MySQL EXPLAIN statement

Recently I had been having trouble with queries on a certain table in a system that I've been maintaining. I had gone through just about every excuse for why queries on the table could be performing so slowly : the machine was slow (DB running on a VM), the webserver was slow (also running on a VM), I wasn't using the native libraries (webserver was Tomcat), I had other processes running in the background (I didn't). Then I ran across a tip on a forum suggesting usage of the MySQL EXPLAIN statement. I had known all about it for the longest time, but it never occurred to me to actually use it (I think I'm that good at writing queries, turns out : I'm wrong). After using the EXPLAIN statement, I found out that the query processor was using a suboptimal query plan which utilized an index I had added with the intent of improving performance (the index had a fairly high arity, so choosing to use it was sketchy at best in the first place). Most DBMSs should have a similar functionality built in. I think that'll be the first place I go in future.

Ubuntu 9.04 servers slow to login

Recently our production system's servers have been getting progressively slower, and it has finally gotten to the point where it's merited my full attention to remedy the situation. In my research on the problem, one of the things I came across was how incredibly slow the logins were (among other problems). After watching top during numerous logins, I saw that console-kit-daemon was going horribly slow and shooting the sshd CPU usage through the roof. After some time googling for issues related to console-kit-daemon, I found that many people were getting errors in their /var/log/daemon.log file regarding console-kit-daemon being unable to initialize policykit. After installing policykit, my logins to my production servers are now lightning fast

Keeping your servers up to date

As I've previously mentioned on this blog, our company uses Ubuntu for our servers. I won't re-iterate the reasons why in this post, you can search this blog using an Ubuntu tag if you're interested in them. Our servers have uptimes of months and months, and as a result, the clocks on the machines tend to drift over time, which has inspired me to start using NTP to keep the clocks synchronized. A quick Google search yielded the desired results. In order to manually synchronize with NTP, you can run the following commands :

sudo /etc/network/if-up.d/ntpdate

sudo ntpdate pool.ntp.org

Obviously, entering this command every day or every week gets tiresome and stupid, so you can get cron to schedule this daily for you by running the following commands :

echo "sudo ntpdate ntp.ubuntu.com" >> /etc/cron.daily/ntpdate
chmod 755 /etc/cron.daily/ntpdate

Tomcat keystore : too many open files - Continued

Further to my last post, it seems there was another, larger underlaying problem that was causing the exceptionally high number of connections to our servers. One of our clients "required" (I use that term loosely because they really didn't the information) extra information for transactions that was not included in the optimized change metadata that they had been instructed to query for in order to update their transactions. So instead of just querying for the update metadata, they would do that, and then they'd query for each individual transaction. Assume we page our metadata at 100 transactions / page. For example, if we were to have a batch of 800 transactions submitted by the client, instead of making 800 / 100 = 8 calls to our server to update the transactions in the batch, they'd have 8 + (800 * 1) = 808 calls to update their system. They were effectively launching a Denial of Service attack on our servers each time they wanted to update a batch of transactions. Needless to say I consulted with them on the issue and updated our change metadata to include the information they "need" (which they've already got in their system), and they've updated their system to take the number of requests down to the proper level to update their transactions. So let this be a lesson to anybody reading this blog post that has to develop systems that deal with external clients : ensure your clients fully understand the purpose and intent of all the features of our system before they start developing for it and using it.

Too many open sockets error in Tomcat 5.5

Our company recently started a new project. Our primary client is the first one to use it, and use they have. I've suspected they've been putting an unusually high load on our servers, and tonight it was confirmed when our server stopped handling requests, refusing them and then generating "Too many open files" errors in the Tomcat log files referring to my Tomcat SSL keystore. After doing some brief research on the error, I've discovered that this can happen when the Tomcat element in server.xml is configured with too few 'maxThreads' and a too low an 'acceptCount'. I've since tripled the number of threads and acceptable connections. Hopefully this will resolve things.

XML namespace error with Spring WS

Today I ran into a strange error trying to access a webservice via Spring WS (Spring Web Services). The exception looked like the following :

org.springframework.ws.soap.saaj.SaajSoapEnvelopeException: Could not access envelope: Unable to create envelope from given source: ; nested exception is com.sun.xml.messaging.saaj.SOAPExceptionImpl: Unable to create envelope from given source: 
Caused by: 
com.sun.xml.messaging.saaj.SOAPExceptionImpl: Unable to create envelope from given source: 
 at com.sun.xml.messaging.saaj.soap.EnvelopeFactory.createEnvelope(EnvelopeFactory.java:95)
 at com.sun.xml.messaging.saaj.soap.ver1_1.SOAPPart1_1Impl.createEnvelopeFromSource(SOAPPart1_1Impl.java:51)
 at com.sun.xml.messaging.saaj.soap.SOAPPartImpl.getEnvelope(SOAPPartImpl.java:106)
 at org.springframework.ws.soap.saaj.Saaj13Implementation.getEnvelope(Saaj13Implementation.java:145)
 at org.springframework.ws.soap.saaj.SaajSoapMessage.getEnvelope(SaajSoapMessage.java:84)
 at org.springframework.ws.soap.AbstractSoapMessage.getSoapHeader(AbstractSoapMessage.java:42)
 at org.springframework.ws.soap.server.SoapMessageDispatcher.handleRequest(SoapMessageDispatcher.java:91)
 at org.springframework.ws.server.MessageDispatcher.dispatch(MessageDispatcher.java:189)
 at org.springframework.ws.server.MessageDispatcher.receive(MessageDispatcher.java:166)
 at org.springframework.ws.transport.support.WebServiceMessageReceiverObjectSupport.handle(WebServiceMessageReceiverObjectSupport.java:78)
 at org.springframework.ws.transport.http.WebServiceMessageReceiverHandlerAdapter.handle(WebServiceMessageReceiverHandlerAdapter.java:60)
 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:819)
 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:754)
 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:399)
 at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:364)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
 at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
 at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
 at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
 at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
 at java.lang.Thread.run(Unknown Source)
Caused by: javax.xml.transform.TransformerException: org.w3c.dom.DOMException: NAMESPACE_ERR: An attempt is made to create or change an object in a way which is incorrect with regard to namespaces.
 at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(Unknown Source)
 at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(Unknown Source)
 at com.sun.xml.messaging.saaj.util.transform.EfficientStreamingTransformer.transform(EfficientStreamingTransformer.java:371)
 at com.sun.xml.messaging.saaj.soap.EnvelopeFactory.createEnvelope(EnvelopeFactory.java:83)
 ... 30 more
Caused by: org.w3c.dom.DOMException: NAMESPACE_ERR: An attempt is made to create or change an object in a way which is incorrect with regard to namespaces.
 at com.sun.org.apache.xerces.internal.dom.AttrNSImpl.setName(Unknown Source)
 at com.sun.org.apache.xerces.internal.dom.AttrNSImpl.(Unknown Source)
 at com.sun.org.apache.xerces.internal.dom.CoreDocumentImpl.createAttributeNS(Unknown Source)
 at com.sun.xml.messaging.saaj.soap.SOAPDocumentImpl.createAttributeNS(SOAPDocumentImpl.java:142)
 at com.sun.org.apache.xerces.internal.dom.ElementImpl.setAttributeNS(Unknown Source)
 at com.sun.xml.messaging.saaj.soap.impl.ElementImpl.setAttributeNS(ElementImpl.java:1190)
 at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.startElement(Unknown Source)
 at com.sun.org.apache.xml.internal.serializer.ToXMLSAXHandler.closeStartTag(Unknown Source)
 at com.sun.org.apache.xml.internal.serializer.ToSAXHandler.flushPending(Unknown Source)
 at com.sun.org.apache.xml.internal.serializer.ToXMLSAXHandler.startElement(Unknown Source)
 at org.xml.sax.helpers.XMLFilterImpl.startElement(Unknown Source)
 at com.sun.xml.messaging.saaj.util.RejectDoctypeSaxFilter.startElement(RejectDoctypeSaxFilter.java:157)
 at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(Unknown Source)
 at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(Unknown Source)
 at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
 at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
 at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
 at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
 at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
 at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
 at org.xml.sax.helpers.XMLFilterImpl.parse(Unknown Source)
 at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(Unknown Source)
 ... 34 more

As it turns out, the Java 6 JDK comes with its own integrated versions of Apache Xerces and Apache Xalan. The problem is that the integrated versions are old. Updating your project's POM to ensure versions of Apache Xerces >= 2.8.1 and Apache Xalan >= 2.7.0 are in your classpath will remedy the problem.

Some helpful troubleshooting tips for SFTP jails

Further to my previous post on SFTP jails, I've run across a few issues. When logging in via command line after first setting up the jail, you may encounter immediate disconnects with the response "Connection Closed". One possible cause of this is missing files, specifically "/lib64/ld-linux-x86-64.so.2" under the jail. There are other files that can possibly be missing, but that's a biggie if you're running a 64-bit kernel. If you're running WinSCP, you may also encounter the error message "Is the host running a SFTP server?"

A quick note on intercepting annotations with Spring AOP

Spring AOP is incredibly powerful. One of the most powerful features of the framework is that it lets you intercept methods that are decorated with particular annotations using the following AOP expression :

@annotation(my.package.MyAnnotation)

This can be used in place of :

execution(public * my.package.MyService.serviceMethod(*))

...or in combination with it. But one important point : the annotation being intercepted must be in service method implementations (ie concrete class implementations), not on the service method interface declarations! Otherwise Spring AOP will not be able to read and intercept the annotated methods / classes

Setting up Microsoft Outlook 2007 with Microsoft Exchange

...via RPC over HTTPS :

1. Ensure you have your root certificate in your trusted authority store in the Microsoft Management Console (mmc.exe)
2. Ensure you have your personal certificate in your personal key store in the Microsoft Management Console (mmc.exe)
3. Ensure you've got the correct server settings

Setting up a VPN connection to an Astaro security applicance on Mac OS X

So I finally got a working VPN configuration to be able to connect my shiny new MacBook Pro to our VPN on our production system which uses an Astaro firewall appliance. Turns out it's fairly easy too :

• Go to your Astaro firewall's user profile page, ie login as a user, and download the key / OpenVPN configuration package for your router. The great thing about these appliances is that they provide the package for you right from the device


• Download Tunnelblick. It's an (apparently very easy to use) GUI front end for OpenVPN on Mac OS X. The latest version (as of the time of this writing) is 3.0 beta 10. Tunnelblick is hosted on Google Code. The installation's even easier. Load up the disk image, and drag the sole application icon into your applications folder.


• Open the VPN package you downloaded from your Astaro firewall appliance, and copy everything in it to the ~/Library/openvpn folder created by the Tunnelblick installation


• Tunnelblick should automatically detect the additional files and provide a listing for the Astaro configuration in its connection list. Once you've got the item in the list, just click on it and it should automagically connect to the Astaro firewall appliance and your VPN connection should be working.

Oh, and make sure you've actually got Tunnelblick started, or else you won't be able to connect ;)

Playing with my new Mac

I recently managed to convince my employer to provide me with a MacBook Pro so that I could start developing in-house iPhone applications for the company. I'm not yet at the point where I'm writing applications, but I am installing tons of stuff on the laptop so that I can use it as my mobile computer for when I'm on the road for work. It certainly has its quirks that I have to get used to over running everything in Windows. This will be a very brief post, but suffice it to say that I've learned a few things :

1) When it comes to Maven, ensure that JAVA_HOME is set in your environment variables.
2) Make sure you're choosing the right JVM. MacOSX comes with a bunch of default JVMs installed, and you can configure them through the Java control panel in Applications -> Utilities

More Hibernate glitches, part 2

I had previously written on an Expected positional parameter glitch in Hibernate when joining between entities using OneToOne and PrimaryKey + ForeignKey columns. It turns out, Hibernate has this problem no matter what field you query on the joined entity if you're quering by another entity. A way around this is to use the ID property of the joined entities and add another association to your HQL / Criteria query.

ie So if you have Person and Address having a OneToOne relationship

public class Person {
  @OneToOne
  private Address address;
}

... and you want to query for a Person by Address, you would probably write something like :

from Person p where p.address = ?

... in HQL. Well, this is where you start running into the Expected positional parameter glitch. Instead, write your query like this :

from Person p where p.address.id = ?

... and pass in a long / int / whatever type you use for an identifier for Person / Address instead and this will work around the glitch until it can be fixed.

Stupid MySQL tricks

Recently, I found that our secondary server's MySQL partition was starting to get full. After running du -h --max-depth=1 several times recursively, I found that the source was the MySQL binary logs. As it turns out, MySQL comes with a very handy command for purging all log files. If you run :

show master logs

, you'll be given a list of the logs that the MySQL server is currently using. You can clear out old log files (some of which can be very large) by running the command

purge master logs to 'log-name-here -from-display'

. This will remove the old log files from the hard disk and save up some potentially much needed space.

Spring Webflow 2 Quirks

As I recently found out after a marathon debugging session, if you have a <transition> element that executes actions, and any beans involved in an expression evaluation don't exist in your application context, SWF2 will spin it's wheels instead of properly resolving things, leaving your flow in the lurch. At the time of this writing, I'm using Spring Webflow 2.

More Hibernate glitches

I've recently discovered the joy of actually getting OneToOne primary key columns on objects working, so I've started using them more often (where appropriate). Naturally, increased use means increased chances of finding a bug, which I have. It seems there's a parser problem in HQL when it comes to querying on ID columns that are also objects. If you try to query on the object type (ie Person) rather than the ID type (ie Long), you'll get an exception saying something along the lines of :

Expected positional parameter count: 1, actual parameters: [Parent@bec357b] [from Child this where this.id.parent = ?]

The above line is from HHH-2254, but it's representative of the problem I ran across. The problem is that hibernate doesn't properly parse and fill in the parameters in the query. You can get around this by changing the query to use a simple type for ID instead of the object type.

Stupid Hibernate Tricks

I've recently been finding myself looking for a way to get Hibernate to override the default type for strings (varchar) and use char instead in order to boost performance of the database for fields that I know are going to have a fixed length. During my search, I came upon a couple of solutions.

Using annotations

You can use the 'columnDefinition' attribute of the @Column annotation to specify the SQL type directly. This has the unfortunate side effective of possibly reducing the database portability of your application.

Using SQL Dialects

You can override one of Hibernate's built in SQL Dialects and make char() types the default for strings. One other interesting possibility this opens up is that it allows you to only override the definition for certain lengths, ie, you could make any strings less than or equal to 4 characters in length use a char() definition, and the rest could use varchar definitions. This is done using the 'registerColumnType' method of Dialect.

I love Dojo

I have recently discovered the magic that is Dojo. I love it. The widgets that it provides are uber-useful and have really boosted the functionality of our site. And once I integrated it with Spring Webflow 2, using some custom tags I wrote, my development speed shot right up.

Dojo Home Page
Dojo Campus - Great tutorial site

Solved! Finally fixed classpath issues with Maven, Eclipse and JUnit

I have several pieces of code in one of our company's projects that dynamically reads the classpath and scans for classes that have certain annotations and values in those annotations. For the longest time, I was able to unit test these successfully. Then one day, I started getting strange ClassNotFoundExceptions when trying to execute the tests, and I could never figure out why. The project still ran just fine on our servers, so I let the issue slide at the time because I was pressed for time and needed to get other shit done. Overtime, I continued to let the problem bounce up and down over rocks as I tried to unit test certain things and couldn't because of this problem. Today I finally got fed up and wound up investing 3 hours troubleshooting the problem, and here's what happened:

Right around the same time I started getting this problem, I had upgraded my version of the M2Eclipse plugin (which I use to integrate the Maven build system and Eclipse) to a new version. As it turns out, in the intervening versions, the Maven developers changed how Maven integrates with the Eclipse classpath, and if you got the plugin to update your project's Eclipse configuration, it would specify separated output folders for your projects code and your project's test classes, and that's what caused the problem. Separating the two meant I could no longer dynamically resolve my project's model classes in a test environment, because the classpath visitor wouldn't receive the correct source folder from the test environment's classloader. So, the solution as it turned out, was to have Eclipse's output go into the same folder for source and test classes.

Allowing external root access to your MySQL database

...is recommended against in the MySQL documentation, but it can be oh so handy for running scripts and adding databases, tables and views when you can't (or don't want to) log into that remote system on the command line to update it. However, when you try it (at least on a fresh Ubuntu install), you may be greeted with an Error 2003. This happens when your system does not allow root external access. To enable external access, you can run this query (as root) on your server from the command line (must be localhost) :

GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY ('myrootpassword');

* EDIT * : The above statement does not necessarily copy all privileges over to the new entry for 'root'@'%' in the mysql.user table. A better way to accomplish full external root access is the following :

DELETE FROM `mysql`.`user` WHERE User = 'root' AND Host = '%';
INSERT INTO `mysql`.`user` (Host, User, Password, Select_priv, Insert_priv, Update_priv, Delete_priv, Create_priv, Drop_priv, Reload_priv, Shutdown_priv, Process_priv, File_priv, Grant_priv, References_priv, Index_priv, Alter_priv, Show_db_priv, Super_priv, Create_tmp_table_priv, Lock_tables_priv, Execute_priv, Repl_slave_priv, Repl_client_priv, Create_view_priv, Show_view_priv, Create_routine_priv, Alter_routine_priv, Create_user_priv, ssl_type, ssl_cipher, x509_issuer, x509_subject, max_questions, max_updates, max_connections, max_user_connections) (SELECT '%', User, Password, Select_priv, Insert_priv, Update_priv, Delete_priv, Create_priv, Drop_priv, Reload_priv, Shutdown_priv, Process_priv, File_priv, Grant_priv, References_priv, Index_priv, Alter_priv, Show_db_priv, Super_priv, Create_tmp_table_priv, Lock_tables_priv, Execute_priv, Repl_slave_priv, Repl_client_priv, Create_view_priv, Show_view_priv, Create_routine_priv, Alter_routine_priv, Create_user_priv, ssl_type, ssl_cipher, x509_issuer, x509_subject, max_questions, max_updates, max_connections, max_user_connections FROM `mysql`.`user` WHERE User = 'root' AND Host = 'localhost');
FLUSH PRIVILEGES;

Setting up MySQL server on Ubuntu

...is really easy. Run the command :

apt-get install -y mysql-server

Once that's done, you'll need to perform some additional configuration and setup the root password. My added configuration involves making table name comparisons all lower case (convenient for queries) and making the server run entirely in utf8. In order to configure the server as such, you'll need to make the following changes :

Add the following lines to the [mysqld] section of the my.cnf configuration :

default-character-set=utf8
default-collation=utf8_general_ci
lower_case_table_names=1

Add the following line to the [mysql] section of my.cnf (note that this is not the same as the [mysqld] section, the difference being the 'd' on the end) :

default-character-set=utf8

In order to have the Ubuntu MySQL installation properly run on external hosts, you'll have to comment out the line that looks like :

bind-address     127.0.0.1

After you've configured the my.cnf file, you'll have to stop the server, and restart it with --skip-grant-tables enabled so that you can have free, unfettered access to the system with privileges disabled. This is required so that you can set the initial root password. Run the following commands as root :

/etc/init.d/mysql stop
mysqld_safe --skip-grant-tables --skip-networking &

The latter command will start the MySQL server with privileges disabled.
Then log in with the command

mysql -u root -h localhost

Once logged in, run the command :

UPDATE `mysql`.`user` SET Password = PASSWORD('thepassword') WHERE User = 'root';

This will set the user password to 'thepassword' (though I recommend you don't use that exact password). Once you've set the root password, exit mysql and run the command

/etc/init.d/mysql restart

This will restart the server as usual, so that you'll no longer have unlimited privileges (and neither will anyone else).

Setting up an SSH Server on Ubuntu

Ubuntu is usually pretty good about coming pre-configured with everything you need for your system, but one thing I've found that it's lacking (at least the server distribution is, anyway) is a pre-setup SSH server. Fortunately though, it's quite easy to set one up. All you need to do is issue the command:

apt-get install openssh-server

...as root. If you get an error to the effect of :

Package does not exist

...then you'll have to run :

apt-get update

...to update your system's packages first.

Configuring MySQL for table case-insensitivity

While trying to add a recent update to our systems, I noticed that our demo system wouldn't start, which was very strange considering I had no problems on my local test system. I eventually traced the problem down to MySQL not being able to find certain tables. This was because I had created the tables in a different case than the Quartz library was expecting. My local testing box is a Windows box whereas our demo and production systems run Linux, the difference being that my Windows MySQL installation has case-insensitivity on by default, whereas the Linux installations do not. In order to remedy this, I had to explicitly add a line to my my.ini / my.cnf configurations :

lower_case_table_names=1

You can determine the case-sensitivity of your own MySQL installation by logging in with the command line client or running the query browser and entering the following command :

SHOW VARIABLES LIKE 'lower_case%'

Integrating Quartz and Spring using persistent jobs

I've recently found myself having a lot of jobs running in the background of our Java applications, often requiring changes to the scheduling based on my boss' whims. Combine this with the fact that our system's API is now seeing heavy use, and having the triggers configured in the Spring application context (and thus requiring a restart in order to change them) just doesn't cut it any more. Thus, I now find myself needing persistent jobs. However, there's not a lot of documentation out there for dealing with Quartz' persistent job feature in Spring, so I'm going to hopefully provide some help. To start, you need to create the quartz tables in whatever database you're going to be using. There are scripts for creating these tables in the Quartz distribution available on their website for whatever database you may be using. For convenience, I've copied the MySQL Inno DB script here :

DROP TABLE IF EXISTS QRTZ_JOB_LISTENERS;
DROP TABLE IF EXISTS QRTZ_TRIGGER_LISTENERS;
DROP TABLE IF EXISTS QRTZ_FIRED_TRIGGERS;
DROP TABLE IF EXISTS QRTZ_PAUSED_TRIGGER_GRPS;
DROP TABLE IF EXISTS QRTZ_SCHEDULER_STATE;
DROP TABLE IF EXISTS QRTZ_LOCKS;
DROP TABLE IF EXISTS QRTZ_SIMPLE_TRIGGERS;
DROP TABLE IF EXISTS QRTZ_CRON_TRIGGERS;
DROP TABLE IF EXISTS QRTZ_BLOB_TRIGGERS;
DROP TABLE IF EXISTS QRTZ_TRIGGERS;
DROP TABLE IF EXISTS QRTZ_JOB_DETAILS;
DROP TABLE IF EXISTS QRTZ_CALENDARS;
CREATE TABLE QRTZ_JOB_DETAILS(
JOB_NAME VARCHAR(200) NOT NULL,
JOB_GROUP VARCHAR(200) NOT NULL,
DESCRIPTION VARCHAR(250) NULL,
JOB_CLASS_NAME VARCHAR(250) NOT NULL,
IS_DURABLE VARCHAR(1) NOT NULL,
IS_VOLATILE VARCHAR(1) NOT NULL,
IS_STATEFUL VARCHAR(1) NOT NULL,
REQUESTS_RECOVERY VARCHAR(1) NOT NULL,
JOB_DATA BLOB NULL,
PRIMARY KEY (JOB_NAME,JOB_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_JOB_LISTENERS (
JOB_NAME VARCHAR(200) NOT NULL,
JOB_GROUP VARCHAR(200) NOT NULL,
JOB_LISTENER VARCHAR(200) NOT NULL,
PRIMARY KEY (JOB_NAME,JOB_GROUP,JOB_LISTENER),
INDEX (JOB_NAME, JOB_GROUP),
FOREIGN KEY (JOB_NAME,JOB_GROUP)
REFERENCES QRTZ_JOB_DETAILS(JOB_NAME,JOB_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_TRIGGERS (
TRIGGER_NAME VARCHAR(200) NOT NULL,
TRIGGER_GROUP VARCHAR(200) NOT NULL,
JOB_NAME VARCHAR(200) NOT NULL,
JOB_GROUP VARCHAR(200) NOT NULL,
IS_VOLATILE VARCHAR(1) NOT NULL,
DESCRIPTION VARCHAR(250) NULL,
NEXT_FIRE_TIME BIGINT(13) NULL,
PREV_FIRE_TIME BIGINT(13) NULL,
PRIORITY INTEGER NULL,
TRIGGER_STATE VARCHAR(16) NOT NULL,
TRIGGER_TYPE VARCHAR(8) NOT NULL,
START_TIME BIGINT(13) NOT NULL,
END_TIME BIGINT(13) NULL,
CALENDAR_NAME VARCHAR(200) NULL,
MISFIRE_INSTR SMALLINT(2) NULL,
JOB_DATA BLOB NULL,
PRIMARY KEY (TRIGGER_NAME,TRIGGER_GROUP),
INDEX (JOB_NAME, JOB_GROUP),
FOREIGN KEY (JOB_NAME,JOB_GROUP)
REFERENCES QRTZ_JOB_DETAILS(JOB_NAME,JOB_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_SIMPLE_TRIGGERS (
TRIGGER_NAME VARCHAR(200) NOT NULL,
TRIGGER_GROUP VARCHAR(200) NOT NULL,
REPEAT_COUNT BIGINT(7) NOT NULL,
REPEAT_INTERVAL BIGINT(12) NOT NULL,
TIMES_TRIGGERED BIGINT(7) NOT NULL,
PRIMARY KEY (TRIGGER_NAME,TRIGGER_GROUP),
INDEX (TRIGGER_NAME, TRIGGER_GROUP),
FOREIGN KEY (TRIGGER_NAME,TRIGGER_GROUP)
REFERENCES QRTZ_TRIGGERS(TRIGGER_NAME,TRIGGER_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_CRON_TRIGGERS (
TRIGGER_NAME VARCHAR(200) NOT NULL,
TRIGGER_GROUP VARCHAR(200) NOT NULL,
CRON_EXPRESSION VARCHAR(120) NOT NULL,
TIME_ZONE_ID VARCHAR(80),
PRIMARY KEY (TRIGGER_NAME,TRIGGER_GROUP),
INDEX (TRIGGER_NAME, TRIGGER_GROUP),
FOREIGN KEY (TRIGGER_NAME,TRIGGER_GROUP)
REFERENCES QRTZ_TRIGGERS(TRIGGER_NAME,TRIGGER_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_BLOB_TRIGGERS (
TRIGGER_NAME VARCHAR(200) NOT NULL,
TRIGGER_GROUP VARCHAR(200) NOT NULL,
BLOB_DATA BLOB NULL,
PRIMARY KEY (TRIGGER_NAME,TRIGGER_GROUP),
INDEX (TRIGGER_NAME, TRIGGER_GROUP),
FOREIGN KEY (TRIGGER_NAME,TRIGGER_GROUP)
REFERENCES QRTZ_TRIGGERS(TRIGGER_NAME,TRIGGER_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_TRIGGER_LISTENERS (
TRIGGER_NAME VARCHAR(200) NOT NULL,
TRIGGER_GROUP VARCHAR(200) NOT NULL,
TRIGGER_LISTENER VARCHAR(200) NOT NULL,
PRIMARY KEY (TRIGGER_NAME,TRIGGER_GROUP,TRIGGER_LISTENER),
INDEX (TRIGGER_NAME, TRIGGER_GROUP),
FOREIGN KEY (TRIGGER_NAME,TRIGGER_GROUP)
REFERENCES QRTZ_TRIGGERS(TRIGGER_NAME,TRIGGER_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_CALENDARS (
CALENDAR_NAME VARCHAR(200) NOT NULL,
CALENDAR BLOB NOT NULL,
PRIMARY KEY (CALENDAR_NAME))
TYPE=InnoDB;

CREATE TABLE QRTZ_PAUSED_TRIGGER_GRPS (
TRIGGER_GROUP VARCHAR(200) NOT NULL,
PRIMARY KEY (TRIGGER_GROUP))
TYPE=InnoDB;

CREATE TABLE QRTZ_FIRED_TRIGGERS (
ENTRY_ID VARCHAR(95) NOT NULL,
TRIGGER_NAME VARCHAR(200) NOT NULL,
TRIGGER_GROUP VARCHAR(200) NOT NULL,
IS_VOLATILE VARCHAR(1) NOT NULL,
INSTANCE_NAME VARCHAR(200) NOT NULL,
FIRED_TIME BIGINT(13) NOT NULL,
PRIORITY INTEGER NOT NULL,
STATE VARCHAR(16) NOT NULL,
JOB_NAME VARCHAR(200) NULL,
JOB_GROUP VARCHAR(200) NULL,
IS_STATEFUL VARCHAR(1) NULL,
REQUESTS_RECOVERY VARCHAR(1) NULL,
PRIMARY KEY (ENTRY_ID))
TYPE=InnoDB;

CREATE TABLE QRTZ_SCHEDULER_STATE (
INSTANCE_NAME VARCHAR(200) NOT NULL,
LAST_CHECKIN_TIME BIGINT(13) NOT NULL,
CHECKIN_INTERVAL BIGINT(13) NOT NULL,
PRIMARY KEY (INSTANCE_NAME))
TYPE=InnoDB;

CREATE TABLE QRTZ_LOCKS (
LOCK_NAME VARCHAR(40) NOT NULL,
PRIMARY KEY (LOCK_NAME))
TYPE=InnoDB;

INSERT INTO QRTZ_LOCKS values('TRIGGER_ACCESS');
INSERT INTO QRTZ_LOCKS values('JOB_ACCESS');
INSERT INTO QRTZ_LOCKS values('CALENDAR_ACCESS');
INSERT INTO QRTZ_LOCKS values('STATE_ACCESS');
INSERT INTO QRTZ_LOCKS values('MISFIRE_ACCESS');
commit; 

Once this is done, you'll need to integrate Quartz with Spring. If you're using Maven 2, getting Quartz into your project is as simple as adding the following snippet to the <dependencies> section of your pom.xml configuration file.

<dependency>
  <groupId>opensymphony</groupId>
  <artifactId>quartz</artifactId>
  <version>1.6.0</version>
  <scope>provided</scope>
</dependency>

Note that you're going to need Quartz version 1.6.0 to work with Spring 2.5.3 or greater, otherwise you can use Quartz 1.5.x. After you've got Quartz into your project, you'll need to define a Scheduler that accesses your database to schedule your jobs. Fortunately, Spring happens to come with a handy FactoryBean for defining Quartz schedulers. I've used the following :

<bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
  <property name="jobFactory">
    <bean class="org.springframework.scheduling.quartz.SpringBeanJobFactory"/>
  </property>
  <property name="dataSource" ref="mainDataSource" />
  <property name="transactionManager" ref="mainDataSourceTransactionManager" />
  <property name="quartzProperties">
    <util:properties location="/WEB-INF/config/quartz.properties"/>
  </property>
  <property name="applicationContextSchedulerContextKey" value="applicationContext"/>
  <property name="waitForJobsToCompleteOnShutdown" value="true" />
</bean>

The above Spring beans configuration snippet requires some explanation, so let's go through it.

• The property 'jobFactory' is a Spring implementation of the Quartz JobFactory interface. When the scheduler encounters a trigger in the database that's to be fired, it loads the corresponding JobDetails from the database, loads it into a JobDetail object, places that JobDetail object into a TriggerFiredBundle, and passes the TriggerFiredBundle to the JobFactory interface to obtain a Job that's to be run. Now, you might think that because of the name of Spring's JobFactory implementation, it's going to do something with a bean defined in the Spring ApplicationContext, right ? Wrong. What this implementation does is get the Job class provided by JobDetail.getClass(), instantiate a new instance of it with a default no-arg constructor, possibly populate it with properties, and then run the Job. Which sucks, and is kind of useless, because no Jobs I need can do so without getting something from Spring's ApplicationContext. More on this later.


• The 'dataSource' property should be the javax.sql.DataSource used by your application to connect to whatever database you're using that stores the persistent Jobs in the tables used by Quartz.


• The 'transactionManager' property should be set to a org.springframework.transaction.PlatformTransactionManager implementation that's used to demarcate transactions in the database. If you don't have one for your dataSource already defined, then it's fortunate that Spring comes with one that you can define and use, like so :
  

  
  <bean id="mainDataSourceTransactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager" p:dataSource-ref="mainDataSource" />
  

  
  


• The 'quartzProperties' property should be configured with a java.util.Properties instance containing configuration values for Quartz. A sample is posted here for you :
  

  
  org.quartz.threadPool.class=org.quartz.simpl.SimpleThreadPool
  org.quartz.threadPool.threadCount=5
  org.quartz.threadPool.threadPriority=4
  
  org.quartz.jobStore.tablePrefix=qrtz_
  org.quartz.jobStore.isClustered=false
  org.quartz.jobStore.driverDelegateClass=org.quartz.impl.jdbcjobstore.StdJDBCDelegate
  

  
  This sample contains a few simple properties that should be enough to get you started. There are numerous others that you should look into in the Quartz documentation. The first three properties are for configuring Quartz' thread-pooling capabilities. The latter three are for configuring the database (and access thereto-) that Quartz uses for storing persistent jobs. The table prefix is used to prefix Quartz' tables so that they don't conflict with any pre-existing tables in your database. The 'isClustered' property is used to determine whether Quartz is acting in a cluster. Clustered Quartz configurations are beyond the scope of this article. The 'driverDelegateClass' property is used to determine the class Quartz will use for dealing with your specific dialect of SQL (ie MySQL, MS-SQL, PostgreSQL, etc).


• The 'applicationContextSchedulerContextKey' property sets a key that's used to access the Spring ApplicationContext in the JobExecutionContext given to a Job implementation at run time after the SpringBeanJobFactory has populated it for you. This is important as this property does not have a default value and will not put the ApplicationContext into the JobExecutionContext for you unless you specify one.


• The 'waitForJobsToCompleteOnShutdown' property specifies, well, I think you can figure that one out.

At this point in time, you've got the tables which Quartz requires for persistent jobs defined (and presumably accessible) in your database, you've got the Quartz libraries present in your classpath, and you've got Quartz configured within Spring so that Quartz will run and check the database for jobs to be run. However, we're still missing a few more important pieces of information.

1. JobDetails stored in the database describing jobs to be run


2. Triggers defined in the database for describing when JobDetails will be executed

For the rest of this article, lets assume that you've set your Quartz table prefix as 'qrtz_'. In your database, lets look at the definition of the 'qrtz_job_details' table. It includes columns for defining job_name, job_group, description, job_class_name, is_durable, is_volatile, is_stateful, requests_recovery, and job_data.

The 'job_name' field is, as you've almost certainly guessed, the name of the job that you want to define. The job must also have a 'job_group' specified because triggers can be used to signal the execution of entire groups of jobs at once, not just single jobs. The two of these fields together form a unique key for the table. If you really don't give a shit about grouping jobs, you can just use Quartz' default group name, which is 'DEFAULT'. You also need to set a 'job_class_name'. This value is a fully qualified Java class name that must have a default, no-arg constructor (ie it's a bean, according to the Java Beans specification). This class will get instantiated at run time by the SpringBeanJobFactory and run as a Quartz job. Note that this class, obviously, must implement the org.quartz.Job interface. A decription of the job can be put in the 'description' field if you want to have a log-friendly message available to you. The is_durable, is_volatile, is_stateful, and requests_recovery fields are all (essentially) boolean fields that Quartz defines as being single characters. These fields can have the values 'Y' or 'N'. See the Quartz API for org.quartz.JobDetail for further elaboration on the meaning of these fields. The 'job_data' field is a BLOB object that's used to serialize the 'jobDataMap' (java.util.Map) associated with the JobDetail. In order to populate this field, you'll obviously have to write some JDBC code.

The 'qrtz_job_details' table is, obviously, where you store the information for the org.quartz.Jobs you want to run. Anytime you need to define a new job, you'll need to insert a new row into this table, properly configured of course and paying particular attention to the 'job_class_name' field.

Ok, so assuming you've got a couple rows in this table (ie defined a couple of jobs), now you'll need to schedule them so that, at some point, they'll actually run. This is where triggers come in. Now, in Quartz, there are a few different methods of triggering off Jobs, by far the most common being org.quartz.SimpleTriggers (qrtz_simple_triggers table) and org.quartz.CronTriggers (qrtz_cron_triggers table). SimpleTriggers have their use, but our company uses some pretty complex scheduling at times, so I'm going to do an example of using the cron triggers.

The 'qrtz_cron_triggers' table is pretty simple, it only has four fields : 'trigger_name', 'trigger_group', 'cron_expression' and 'time_zone_id', all of which should be pretty indicative of their content. The 'time_zone_id' field should be a valid id for a java.util.TimeZone, ie 'America/Denver'. See the documentation for that class for more on valid IDs.

Once you've set up a trigger with a valid name, group (ie DEFAULT), cron expression and TimeZone ID, you're pretty much ready to go. When Quartz starts up with your application, it'll consult the 'qrtz_triggers' table and ensure that entries exist for all of your corresponding cron / simple / blob triggers. It'll then proceed to fire off triggers and the Scheduler will pass off jobs to the SpringBeanJobFactory for execution. Now, if you haven't figured it out already, if you've got a lot of jobs, so far from what this article has shown you, you'll have to create a Quartz Job implementation for each job you want to run off, and even then, it'll have to be pretty simple, since you'll have to be able to instantiate it with a no-arg constructor, and so far you've got no way of injecting it with anything from Spring, aside from simple properties that are defined by the 'schedulerContextAsMap' property on the Spring SchedulerFactoryBean. So, what I did was create a class that uses its JobDetail#name as a convention for getting a bean from the application context, assumes it's an org.quartz.Job implementation, and executes it. The code is attached :

public class SpringBeanDelegatingJob implements Job {
 
 private static final Log LOGGER = LogFactory.getLog(SpringBeanDelegatingJob.class);
 
 public static final String APPLICATION_CONTEXT_KEY = "applicationContext";

 @SuppressWarnings("unchecked")
 public void execute(JobExecutionContext arg0) throws JobExecutionException {

  JobDetail jobDetail = arg0.getJobDetail();
  
  String beanName = substringBefore(jobDetail.getName(), "Detail");
  
  if (LOGGER.isInfoEnabled()) {
   LOGGER.info ("Running SpringBeanDelegatingJob - Job Name ["+jobDetail.getName()+"], Group Name ["+jobDetail.getGroup()+"]");
   LOGGER.info ("Delegating to bean ["+beanName+"]");
  }
  
  ApplicationContext applicationContext = null;
  
  try {
   applicationContext = (ApplicationContext) arg0.getScheduler().getContext().get(APPLICATION_CONTEXT_KEY);
  } catch (SchedulerException e2) {
   throw new JobExecutionException("Holy fuck, there was some kind of god-damned problem with the fucking Scheduler", e2);
  }
  
  Job bean = null;
  
  try {
   bean = (Job) applicationContext.getBean (beanName, Job.class);
  } catch (BeansException e1) {
   throw new JobExecutionException("Unable to retrieve target bean that is to be used as a job source", e1);
  }
  
  bean.execute (arg0);
  
  return;
 }

}

Now, this makes the persisted jobs a lot more capable : we can now run org.quartz.Job beans that are declared in our Spring ApplicationContext. What if we want to be able to run arbitrary methods on arbitrary beans as jobs ? Well, we can write an adapter class for that too, quite similar (though not as functional as) Spring's MethodInvokingJobDetailFactoryBean :

public class SpringBeanMethodInvokingJob implements InitializingBean, Job {
 
 private Object targetBean;
 private String targetMethod;

 //Constructors

 public SpringBeanMethodInvokingJob() {
  super();
 }
 
 //Behaviour Methods

 public void execute(JobExecutionContext arg0) throws JobExecutionException {
  
  Method method = null;
  
  try {
   method = targetBean.getClass().getMethod(targetMethod);
  } catch (Exception e) {
   throw new JobExecutionException("Unable to get targetMethod ["+targetMethod+
    "] on bean with class ["+targetBean.getClass().getName()+"]");
  }
  
  try {
   method.invoke(targetBean);
  } catch (Exception e) {
   throw new JobExecutionException("Unable to invoke method ["+method.getName()+"] on bean ["+targetBean.toString()+"]");
  }
  
  return; //done
 }

 public void afterPropertiesSet() throws Exception {
  Assert.notNull(targetBean, "'targetBean' cannot be null");
  Assert.isTrue(isNotBlank(targetMethod), "'targetMethod' cannot be blank");
 }

 //Property Accessors
 
 @Required
 public final void setTargetBean(Object targetBean) {
  this.targetBean = targetBean;
 }

 @Required
 public final void setTargetMethod(String targetMethod) {
  this.targetMethod = targetMethod;
 }

}

Note that the class above is implements org.quartz.Job, not org.quartz.JobDetail as is the product of MethodInvokingJobDetailFactoryBean. I hope this article has been useful for anybody reading it, feel free to comment on it.

The greatest MySQL companion ever

I just recently found out about the 'show processlist' command in MySQL that lets you get a resultset of all the processes MySQL is currently using and what query they're running. Today I was working in top monitoring the performance of our servers as I restarted our production server. MySQL popped up briefly on the top list of running processes and it occurred to me, "Wouldn't it be great of there was something like this for MySQL?". So while I was waiting, I popped open google, and ran a query for a MySQL and top. To my surprise, up came mytop. It's literally top for MySQL and it's so ridiculously useful you wouldn't believe it. Even better, it's got a .deb made for it and it's in the Ubuntu repositories, so installing it is as simple as running :

apt-get install mytop

It's a good day today :)

Setting a user's password in MySQL

I've recently found the need to change a bunch of passwords in MySQL. The command to do it is as follows :

SET PASSWORD FOR 'myuser'@'%.wherever.com' = PASSWORD('newpass');

You can also read the documentation on the MySQL website.

Finding out what MySQL is doing

I was recently updating our production system when I noticed that our main MySQL database was going unusually hard. On a quad-core processor system, it was using up three processors simaltaneously. This prompted me to find out what MySQL is doing, and after being unable to read the logs, I did a Google search and ran across this useful little command :

show processlist

This runs a query (can be run from either the command line or the query browser) and shows you a summary of all the processes that MySQL is currently using.

Migrating from Spring Webflow 1 to Webflow 2

...was relatively painless. At least in the very small app that I'm currently working on as a helper application for dealing with one of our partners' systems. The flow definition migration assistant that comes with Webflow 2 is a huge help. There are, however, a few things to take note of when it comes to differences between Webflow 1 and Webflow 2. They are significantly different beasts to say the least :

• 
  

  
  My configuration went from this (in Webflow 1) :
  

  
  

  
   <flow:registry id="flowRegistry">
    <flow:location path="/WEB-INF/flows/**/*-flow.xml"/>
   </flow:registry>
  
   <flow:executor id="flowExecutor" registry-ref="flowRegistry">
    <!--flow:execution-listeners>
     <flow:listener ref="webflowDebugListener"/>
    </flow:execution-listeners-->
   </flow:executor>
   
   <!--bean id="webflowDebugListener" class="org.springframework.webflow.execution.DebuggingListener"/-->
   
   <bean name="flowController" class="org.springframework.webflow.executor.mvc.FlowController">
    <property name="flowExecutor" ref="flowExecutor" />
    <property name="argumentHandler">
     <bean class="org.springframework.webflow.executor.support.RequestParameterFlowExecutorArgumentHandler" />
    </property>
   </bean>
    

  
  

  
  To this (in Webflow 2) :
  

  
  

  
   <webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices">
    <webflow:flow-location-pattern value="/WEB-INF/flows/**/*-flow.xml"/>
   </webflow:flow-registry>
  
   <webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
    <webflow:flow-execution-listeners>
     <!-- webflow:listener ref="webflowDebugListener"/ -->
     <webflow:listener ref="securityFlowExecutionListener"/>
    </webflow:flow-execution-listeners>
   </webflow:flow-executor>
   
   <bean id="securityFlowExecutionListener" class="org.springframework.webflow.security.SecurityFlowExecutionListener" />
   
   <webflow:flow-builder-services id="flowBuilderServices" view-factory-creator="viewFactoryCreator" conversion-service="webflowConversionService"/>
   
   <bean id="webflowConversionService" class="com.mypackage.modules.springframework.webflow2.ConversionServiceFactoryBean">
    <property name="editorMappings">
     <map>
      <entry key="java.util.Calendar"><idref bean="sqlDateCalendarEditor"/></entry>
     </map>
    </property>
   </bean>
  
   <bean id="viewFactoryCreator" class="org.springframework.webflow.mvc.builder.MvcViewFactoryCreator">
    <property name="viewResolvers">
     <list>
      <ref local="xmlViewResolver"/>
      <ref local="decoratedJstlViewResolver"/>
      <ref local="urlBasedViewResolver"/>
     </list>
    </property>
   </bean>
  
   <bean id="webflowDebugListener" class="org.springframework.webflow.execution.DebuggingListener"/>
   
   <bean name="flowController" class="org.springframework.webflow.mvc.servlet.FlowController">
    <property name="flowExecutor" ref="flowExecutor" />
    <property name="flowUrlHandler">
     <bean class="org.springframework.webflow.context.servlet.DefaultFlowUrlHandler" />
    </property>
   </bean>
    

  
  

  
  Now, you may be asking yourself, "Why would there be more configuration in Spring Webflow 2 ? Doesn't Spring generally improve on things like configuration syntax between major versions ? The answer is, of course, yes. However, there are a number of new features that come with Webflow 2 that need to be configured, hence the extra beans for configuration. Note also, that the syntax has changed. I direct your attention to the added 'flow-' prefixes on element names of the previously existing Webflow elements.
  

  
  


• 
  Webflow 2 has much better, much closer integration with Spring Security, hence the need for SecurityFlowExecutionListener listed above. I haven't had a chance to play around with the new integration between Spring Security 2 and Spring Webflow 2, but I'm quickly getting there.
  


• 
  Thanks to the built in model binding and validation that comes with Spring Webflow 2, there's much less syntax for views that simply bind to a model object on transitions. Instead of having to add in FormActions and adding action elements to the view-state you want them applied to, you can now simply specify a model name for the 'model' attribute of the view state, and Webflow 2 will automatically bind the form object for you (which leads us into our next point). Of course, the Spring developers maintained their usual style of keeping things as configurable as possible, so you can not only choose not to bind the model object for particular state transitions, but you can disable validation as well, using the new 'bind' and 'validate' attributes of Webflow 2 'transition' elements.
  


• 
  Because Webflow 2 can now do binding and validation for us right in the flow definition without having to define FormAction beans in our Spring ApplicationContext, Webflow 2 comes with its own updates to the spring-binding framework, hence the need for the 'webflowConversionService' bean in the configuration above. Now, you're probably saying to yourself right now, "Well what the fuck am I supposed to do with the custom PropertyEditors I wrote for my objects when dealing with Spring / Webflow 1 ?". Don't worry, all is not lost. There's a PropertyEditorConverter class that adapts PropertyEditor implementations to the new Webflow 2 Converter interface. You can use this to interface your editors with Webflow 2, and in fact that's what I did.
  


• 
  Webflow 1 left it up to the Spring framework to resolve and render views. Some people found this inconvenient, so Webflow 2 now allows you to have Webflow directly resolve and render views itself. However, since I'm already using the Spring framework and don't need Webflow's abstraction away from the underlaying framework, I chose to keep the Webflow 1 style of resolution and view rendering, hence the need for the 'viewFactoryCreator' bean above.
  

Once all the new configuration was done and out of the way, it was simply a matter of upgrading my existing flows to the new Webflow 2 syntax, which was almost entirely taken care of by the migrator that comes with Webflow 2. Previously, I used the 'var' element heavily to make use of beans in my Spring ApplicationContext, but the 'var' element has since had its usage completely reworked for Webflow 2, so I'm going to have to refactor a couple of my flows and change my style of design with Webflow 2.

One other feature that I'm learning about as I write this post is the Webflow 2 PersistenceContext. It's a solution for the use case where you want to be able to load objects from a database, and only allow a single user to be able to access them at once, ie you wouldn't want multiple people logging into a database and being able to access data on a particular user at the same time and potentially overwrite each others' changes. I'll post more about that later.

Migrating from Acegi Security to Spring Security 2

In an effort to keep our applications current, I've been looking at upgrading from Acegi Security to Spring Security 2 in one of our smaller applications as a test, to see how well it'd go over for our larger applications. So far, the tests are pretty positive. The main advantage to the migration that I can see is improved Web Service security (which I'll definitely be needing), as well as a considerably simplified configuration syntax. The following is a small migration guide :

0. If you haven't already, update your project to use Spring 2.5.4 or greater. This is necessary because of changes to Spring that Spring Security (as well as other Spring subprojects) requires. If you're using Maven 2, this is dead easy, you need only update the <version> elements of the appropriate dependencies.

1. Change all package references starting with 'org.acegisecurity' to 'org.springframework.security' in your code. If you've architected your system right, this should mean very few changes.

2. In your POM, remove all mention of Acegi security and replace it with the following :

<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-core-tiger</artifactId>
    <version>${spring.security.version}</version>

    <exclusions>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
        </exclusion>

        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-support</artifactId>
        </exclusion>
    </exclusions>

</dependency>
...
<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-taglibs</artifactId>
    <version>${spring.security.version}</version>

    <exclusions>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
        </exclusion>

    </exclusions>
</dependency>

The exclusions are necessary to prevent Spring 2.0.x dependencies from being unnecessarily pulled in.

3. Go through your JSPs and remove all xmlns:authz="..." declarations and replace them with :

    xmlns:security="http://www.springframework.org/security/tags"

4. Go through your applicationContext*.xml files and replace any constants you may have referring to Acegi security with their proper Spring Security 2 counterparts. This means replacing the package prefixes 'org.acegisecurity' with 'org.springframework.security' and in some cases replacing ACEGI with SPRING_SECURITY in some static constant names.

This migration guide was based on (and expanded from) the one provided by Matt Raible. If you get the time, I recommend you check out his site, he has a lot of good wisdom and examples to share.

On Hibernate UserTypes

Hibernate UserTypes are a great way for persisting complex classes which may require more than one column in a table in order to be properly represented in a database. Many people have used them successfully in order to be able to simplify storage of complex objects and thus simplify their applications at the same time. One simpler use case of them was to create Enum types before support for Java 5+ enums came along.
Now, you'd think that once you've got Java 5 support with Hibernate, you'd never have to use such a simple use case again because you've got the Enums themselves, along with the @Enumerated annotation you can place on fields and properties, right ? Wrong. I've recently started migrating my projects to Spring Security from Acegi Security, and I've found that in the process, they've made the GrantedAuthority interface extend Comparable. This conflicts with the fact that Java 5+ Enums already implemented the Comparable interface with a generic parameter, and as such your code won't compile if you have an Enum that also implements GrantedAuthority, such as the following :

public enum Role implements GrantedAuthority, ConfigAttribute
{
 ROLE_ADMINISTRATOR;

 public String getAuthority() {
  return name();
 }

 public String getAttribute() {
  return name();
 }

 public String getMessageKey() {
  return "enum.Role.".concat(name());
 }
}

In order to remedy the conflict, I've had to convert my nice, pretty, simple Enum into a class, and simulate Java 5+'s enum behaviour, like so :

public final class Role implements GrantedAuthority, ConfigAttribute, Serializable, Cloneable {

 private static final long serialVersionUID = 1L;

 public static final Role ROLE_ADMINISTRATOR = new Role(0, "ROLE_ADMINISTRATOR");

 private static final Role[] VALUES = new Role[] {
  ROLE_ADMINISTRATOR
 };
 
 private static final Map NAME_MAPPINGS = new HashMap();
 
 static {
  Arrays.sort(VALUES, new Comparator() {
   public int compare(Role o1, Role o2) { 
    return o1.ordinal - o2.ordinal;
   }
  });
  
  for (Role r : VALUES) {
   NAME_MAPPINGS.put (r.getName(), r);
  }
 }
 
 private int ordinal;
 private String name;

 //Constructors

 /*
  * DO NOT EVER USE THIS! It exists only for serialization purposes.
  */
 public Role() {
  super();
 }
 
 private Role(Role r) {
  this(r.ordinal, r.name);
 }

 private Role(int ordinal, String name) {
  super();
  this.ordinal = ordinal;
  this.name = name;
 }

 //Behaviour Methods

 public int compareTo(Object o) {

  if (o == null || o.getClass() != Role.class) {
   throw new IllegalArgumentException(
     "Comparison object may not be null, and must be a Role");
  }

  return this.ordinal - ((Role) o).ordinal;
 }
 
 public String getAuthority() {
  return getName();
 }

 public String getAttribute() {
  return getName();
 }

 //Pseudo-properties

 public String getMessageKey() {
  return "enum.Role.".concat(getName());
 }
 
 //Property Accessors

 public final int getOrdinal() {
  return this.ordinal;
 }

 public final String getName() {
  return this.name;
 }

 //Helper Methods
 
 public static final int hashCode(Role r) {
  return r == null ? 0 : r.hashCode();
 }
 
 public static final boolean equals(Role x, Role y) {
  return x == null ? (y == null) : x.equals(y);
 }
 
 public static final Role clone(Role r) {
  return r == null ? null : r.clone();
 }
 
 public static final Role[] values() {
  return VALUES;
 }
 
 public static final Role valueOf(String s) throws IllegalArgumentException {
  
  String key = defaultString(s).toUpperCase();
  
  if (NAME_MAPPINGS.containsKey(key)) {
   return NAME_MAPPINGS.get(key);
  } else {
   throw new IllegalArgumentException("No role by the name ["+s+"] exists");
  }
 }
 
 //Object Overrides
 
 @Override
 public String toString() {
  return new StringBuffer().append(this.name)
   .append("(").append(this.ordinal).append(")")
   .toString();
 }

 @Override
 public Role clone() {
  return new Role(this);
 }

 @Override
 public int hashCode() {
  final int prime = 31;
  int result = 1;
  result = prime * result + ((this.name == null) ? 0 : this.name.hashCode());
  result = prime * result + this.ordinal;
  return result;
 }

 @Override
 public boolean equals(Object obj) {
  if (this == obj)
   return true;
  if (obj == null)
   return false;
  if (getClass() != obj.getClass())
   return false;
  final Role other = (Role) obj;
  if (this.name == null) {
   if (other.name != null)
    return false;
  } else if (!this.name.equals(other.name))
   return false;
  if (this.ordinal != other.ordinal)
   return false;
  return true;
 }

}

Once this was done, I created a Hibernate UserType implementation for Role, so that Hibernate could persist Roles as Integers, just as was already being done for the Enum version of Role:

public class RoleUserType implements UserType {

 private static final int[] SQL_TYPES = new int[] { Types.INTEGER };
 
 public static final String HIBERNATE_TYPE_NAME = "RoleUserType";

 public Object deepCopy(Object value) throws HibernateException {
  return value;
 }

 public Object assemble(Serializable cached, Object owner) throws HibernateException {
  return (Role)cached;
 }

 public Serializable disassemble(Object value) throws HibernateException {
  return (Role)value;
 }

 public boolean equals(Object x, Object y) throws HibernateException {
  return Role.equals((Role)x, (Role)y);
 }

 public int hashCode(Object x) throws HibernateException {
  return Role.hashCode((Role)x);
 }

 public boolean isMutable() {
  return false;
 }

 public Object nullSafeGet(ResultSet resultSet, String[] names, Object owner) throws HibernateException, SQLException {
  int roleOrdinal = resultSet.getInt(names[0]);
  
  return resultSet.wasNull() ? null : Role.values()[roleOrdinal]; 
 }

 public void nullSafeSet(PreparedStatement statement, Object value, int index)
   throws HibernateException, SQLException {
  if (value == null) {
   statement.setNull(index, Types.INTEGER);
  } else {
   statement.setInt(index, ((Role)value).getOrdinal());
  }
 }

 public Object replace(Object original, Object target, Object owner) throws HibernateException {
  return original;
 }

 @SuppressWarnings("unchecked")
 public Class returnedClass() {
  return Role.class;
 }

 public int[] sqlTypes() {
  return SQL_TYPES;
 }

}

Once the Hibernate UserType implementation was written, it was just a matter of adding my model package to Hibernate's list of annotated packages (using Java 5 after all) :

@TypeDef(name = RoleUserType.HIBERNATE_TYPE_NAME, typeClass = RoleUserType.class)
package com.mypackage.model;

import org.hibernate.annotations.TypeDef;
import eu.alenislimited.acshelper.support.hibernate.RoleUserType;

After defining the Hibernate UserType type, it was then just a matter of going around to all my fields that used Role, and replacing ...

@Enumerated(EnumType.ORDINAL)

... with ...

@Type(type = RoleUserType.HIBERNATE_TYPE_NAME)

Fortunately, doing the conversion was just extra work, and didn't require any special changes to any of my Spring configuration, or even my Hibernate configuration (beyond adding the @TypeDef to my model package and adding it to my Hibernate SessionFactory's list of annotatedPackages).

A first time gem creator's addendum

I recently started researching how to create Ruby Gems because I was working on on a Ruby application that is a reference application for accessing our production system at work, and I wanted to make the specific access code for our production system a Gem in Ruby so that I could just hand it off to future clients who want to integrate with Ruby. Further to that end, I read about the Newgem gem, and so I decided to use it, since it had recently hit 1.0.1. You can read the documentation there, so I won't repeat it here, but there's a couple of things you should do, prior to following their instructions.

1. Set a 'HOME' environment variable if you're using Windows (as I am)


2. gem install cucumber newgem


3. rake config_hoe

The first step is to install newgem, but to also ensure that cucumber is installed as well because it's an unlisted dependency. The second step is to ensure that there's a basic .hoerc file created in your home directory that's ready to go whenever you want to run any tasks on your gem while testing / packaging it. I'm guessing it's automatically created in Linux, but I had to manually set the 'HOME' environment variable and run the configuration task myself in order to have the proper configuration file generated for me to run the tasks for creating and testing my gem.

A quick note on ActiveResource in Ruby on Rails

I've learned a bunch of new things about Ruby on Rails in the past few days, specifically when it comes to RESTful web services.

• ActiveResource uses the built in Ruby XML::Mapping library for its OXM (Object to XML mapping) layer


• Apparently, no Ruby library out there properly handles namespaces. Not a one : REXML, ROXML, XML::Mapping


• ActiveResource can be highly customized to adjust to other RESTful web service schemes, just not when it comes to the generated XML.

Unfortunately this makes it very hard to integrate (in ruby) with the RESTful web service that I've written for our company's production web site. Ironically, I wanted to make the service very Ruby friendly. I really wish there was more in depth documentation out there for Ruby APIs. It would have made things so much easier when I was designing our API, which runs in Java, using JAXB.

A quick note on Maven plugins

I've recently had to go abroad to various other countries for work, and I've found that porting my projects around to various workspaces hasn't been as easy as it otherwise should have been, and here's why : I use Maven, especially the plugins. I've used others, and I've even written my own. I've also learned that one should specify versions of all plugins used, because the behaviour of a plugin may change between versions and if you're unaware of that and you start getting strange behaviour from your project build, this can lead to hours of wasted time trying to figure out what the hell is going on. I'm referring specifically to the maven-war-plugin for building web application WAR files. I had previously left the version unspecified, and when I ported my workspace to my laptop, Maven chose to use a different version of the plugin than that of my desktop, and as a result was including files I didn't want in my WAR file. This led to classpath errors, and me spending several hours trying to find out where the problem was. So in short, always specify versions of the plugins you use to ensure consistent behaviour in your build, wherever you may be working on your project.

Reflection in Ruby

I've recently gotten started going on a Ruby on Rails project for my company, that's meant to be a simple app that we'll throw up and let run for any prospective customers. But I ran into a problem with copying property values between objects, since I'm not as familiar with the language as I'd like to be. The Object type defines a method called 'send' which lets you invoke a method with given arguments. However, I wanted to be able to assign property values via this method, and just sending the name of the property as the name of the method to invoke wasn't working. (Works just fine if you want to get the property). As it turns out, the method for invoking the setter of a property is brain-dead simple : use the name of the method as you'd define it if you were overriding the setter for the property. For example, if you have a property called 'name', you'd define the setter for it as follows :

def name= (name)
  @name = name
end

So if you wanted to set the value of this property reflectively, you'd do something like :

 @person_instance.send "name=", "John Smith"

A moment of developer clarity and zen

I had a moment today where I was just letting my mind wander. It was one of those moments where you have a brilliant idea that just seems so common sense that you can only ask yourself "Why the hell didn't I think of that before ?" This moment of clarity happened to be concerning my horribly slow laptop, with it's horribly old ATA 100, 5400 rpm hard drive. Then it occurred to me : just like with video encoding that I had setup months ago, I could setup a RAM disk to speed up Eclipse by storing my workspace on the RAM disk to speed up access to all the (ridiculous number of) temp files that Eclipse uses. On Ubuntu Linux, it turns out this was ridiculously easy : http://ubuntuforums.org/showthread.php?t=182764

The really amazing part was just how much this sped things up : it took my project build time from 6 mins, 30 seconds down to 35 seconds. And those are real numbers (plus or minus a couple seconds, due to slight variations in repeated builds.)

More JAXB quirks

Today I ran across yet more quirks of JAXB 2.0. I'm getting really tired of running across stupid errors that are difficult to debug because the programmers who wrote JAXB are lazy. Today, I was receiving a java.lang.InternalError when I tried to compile a schema from beans I'd recently refactored. The error I received was something along the lines of "could not escape schema namespace". As it turns out, it was caused by the lack of an @XmlType annotation on the enums I had added to one of my XML serializable beans. I hope this helps anybody who has the same problem.

A quick note about JAXB

JAXB (the Java API for XML Binding) is a great piece of technology (2.x, not 1.x). However, if you're starting an application and your JAXBContext is throwing an exception saying that it's unaware of a given class, there's a quick fix. At this point, I'm guessing you've configured your JAXB context to use a package, and the class that the JAXBContext is unaware of is in the given package, and you're scratching your head as to why it can't seem to find a class that's in the proper package. Well, here's the most probable answer : if you're using package-configured JAXBContexts, you need to have factory methods for all top level elements, similar to the following :

    /**
     * Create an instance of {@link PurchaseOrder }
     * 
     */
    public PurchaseOrder createPurchaseOrder() {
        return new PurchaseOrder();
    }

... assuming that mypackage.PurchaseOrder is the class the JAXBContext is complaining that it's unaware of. This little quirk took me a couple hours to debug because I had just regenerated some web services code using Apache CXF 2.1.1 from an updated WSDL document for an updated Web Service that our company uses. Little did I know, that in comparing the two ObjectFactory files in Eclipse, I had missed copying over certain important functions. Hopefully this helps you.

Pure FTP on Ubuntu

Pure FTP is a great FTP server and I love it because it's ridiculously fast, reliable and works well for our company. The only problem is that it's tricky to configure on Ubuntu because just like with numerous other programs, the people at Ubuntu, in their infinite wisdom, felt the need to fuck with the program's default way of doing things. Specifically, in Ubuntu, command line arguments for starting the FTP service are done through individual files for each command line option you want the service to be started with, with values for the options placed inside each of the files. This is a stupid way of doing things, but that's not the topic of this post.

The problem I've been having lately is that I recently deployed new projects within our production network, and these new projects required access to the FTP server, and aren't on the same box as the server, as is the sole other project that has been using the FTP server. I'd been getting problems trying to connect to the server from any LAN box, but not any external boxes nor the machine itself (localhost). The error I got back was "421 Service not available". I googled around for hours and found nothing useful, until I started realizing that other people were getting 421 errors when their PureFTP instance was misconfigured, but with different messages, and then it got me thinking that maybe my instance was somehow misconfigured.

I re-read the documentation for PureFTP and after an hour or so, it hit me that the server does reverse lookups to resolve fully qualified names, and such resolution doesn't work properly on our network (for good reasons that I'm not going to go into). After disabling reverse DNS resolution with the -H startup option (`echo "yes" >> DontResolve` in the configuration directory in Ubuntu), the problem went away.

I hope this helps anybody else who runs into the same problem.

More Tomcat quirks

I recently ran across a problem with receiving a LinkageError in one of my web applications. The problem occurred when Acegi security tried to use libraries that were not yet loaded and tried to load them itself. Strangely, the error only occurred while using my RESTful API with a Spring Framework controller. If I logged in through my web interface which uses Acegi and Spring MVC, then the linkage error didn't occur.

After numerous hours of Googling around, I found a small company's JIRA issue tracker that reported the same bug, but also that it only occurred when using the security manager. After disabling the security manager on my own Tomcat instance, I found that the problem went away. I'd very much like to have a better resolution, but it's going to have to do for the time being.

Tomcat quirks

In recent weeks, we've had problems with our company's servers going down because of power problems at our colocation provider. As a result, the fact that Tomcat hadn't been properly configured to boot at startup had really burned us. Consequentially, I've been spending the past few days troubleshooting why the servers wouldn't startup, and ensuring that they do come up properly at boot time in future. The following are some of the things I've run across.

• 
  The JAVA_HOME and JRE_HOME variables must be set. If they're not, then Tomcat won't start, at least on Ubuntu Gutsy Gibbon Server. This is a problem I encountered with the default installation of JIRA on one of our production servers.
  


• 
  When using EhCache with Hibernate, the tmp directories don't get deleted, regardless of whether or not Tomcat is shutdown properly. This will block the container from starting up again, so these temp files must be deleted. I encountered this problem with my own applications.
  

Finally! The trick to proper Java Date and Calendar formatting

It's well documented in the Java API as well as numerous forums and blogs, that the Java API is not properly implemented, and in some respects flat out broken, hence why Java 7 is going to have a brand spanking new Date/Time API based on the Joda Time library hosted at sourceforge.net. In implementing Dates / TimeZones in Java, the developers of Java saw fit to separate time zones from date implementations because, really, a date is just a number of milliseconds from Jan 1, 1970 at 00:00:00.000 GMT in the morning. This is a noble goal which I whole heartedly agree with : dates should be represented separately from their timezones because the printed representation of a date will change depending on time zone, whereas no matter where you are in the world, the number of milliseconds from the Epoch has not changed. However, the Java developers implemented this concept poorly. They chose to attach TimeZones to Calendars and then not have them affect any of the time fields, which is fine. But the TimeZone attached to a calendar is not used when using a DateFormat directly. Here's the key : the DateFormat object uses its own internal TimeZone during formatting (which it takes from the currently running JVM) by default. In order to format using the TimeZone attached to a Calendar, you have to explicitly set the TimeZone of the DateFormat to that of the Calendar instance you want to format.