Why you should always export your sources with your Java projects

With the advent of popular and widespread Maven 2 adoption, there's no reason you shouldn't be using it to build your open-source or closed source Java projects. With that in mind, it's dead easy to use Maven's 'source' plugin to automatically generate a separate JAR with your project's sources in it when you package and deploy your project. Posting the sources with your project not only allows other people to easily debug their code while using your project, but also serves as a backup in the event of a catastrophic failure of a computer hosting your code for which you did not have proper backup procedures already in place. In the event that you couldn't tell, that happened to me tonight.

JAXB schemagen - Finally got it working

For those not in the know, schemagen is a program that comes as part of the Java Web Services Developer Pack and it's used to generated XML schemas from JAXB annotations on Java beans. It so happens that the creators of the JAXB reference implementation also made a Maven 2 plugin for this program. I had previously attempted to use it to generate schemas in my initial attempts with JAXB, but had been presented with a slough of unfriendly exceptions being thrown at me whenever I ran the plugin. Not having the time back then to really play around with it and being considerably less experienced with JAXB, I had to shelve it and find other, less satisfying solutions to my problems with generating documentation.

Recently, I've had to come back to using JAXB because I'm making a RESTful Web Services API that leverages the power of both JAXB and Hibernate to do all my heavy lifting for me. This time around, I wasn't willing to tolerate a lack of schema to give to our users of the API, because it would mean a lot more work for them, and a lot more work for me. This time, I decided to be persistent and dig around the jaxb-schemagen plugin to make sure I could get it working. I'm proud to say that my perseverance paid off, and I now have my RESTful API schema being automatically generated for my application. Here are the problems and the solutions I ran into when I was trying to get going on this:

NullPointerException

I came across persistent NullPointerExceptions while trying to run the plugin at first. The stack trace indicated that the problem was with apt, the Java annotation processing tool. I later discovered that in order to properly map your classes into XSD schema types, you must specify an @XmlType annotation on *all* of the classes you wish to map (at least with JAXB 2.0, which is the version I'm currently using)

ClassCastException

After I resolved the first problem, I came across another pesky exception that likewise did not provide any useful debugging information. The plugin output indicated that it was finding annotations that it didn't know how to deal with, specifically the Java Persistence API annotations that I was using for Hibernate. After much digging around on Google and some detective work, I discovered that any annotations encountered by the jaxb-schemagen plugin had to be on the Maven runtime classpath. I double checked my POM to find that I had specified the scope of the JPA / Hibernate annotations as 'provided', which instructs Maven not to load them into either the compile or runtime classpaths. The initial reason I had for specifying the dependency scope as 'provided' was so that they would not needlessly get included with my project WAR files. I changed their scope to 'compile' (which also includes 'runtime') and voila, apt could now properly detect the unknown annotations, and get past them to deal with the JAXB annotations it needs to create the XML schema.

If anybody else encounters similar errors with JAXB-schemagen, I hope they find this page and find it useful.

Fixing package retrieval quirks in Ubuntu Gutsy Gibbon Server

In the default installation of Ubuntu Server (Gutsy Gibbon), the default source of packages is the CD-ROM drive. That's fine if you make the assumption that there will always be somebody physically present in order to maintain the servers, but for most server's these days, that's a fallacious assumption. The really bad part about this default, is that there's no way I know of at the time of this writing to override this on the update command. In our company, we have our servers hosted off-site like so many other companies, so everything must be done remotely. Therefore, the CD-ROM as a source for Ubuntu packages is a bad idea. To remedy this, you have to go into the apt-get configuration stored at

/etc/apt/sources.list

, and you'll have to find a line similar to :

deb cdrom:[Ubuntu-Server 7.10 _Gutsy Gibbon_ - Release i386 (20071016)]/ gutsy main restricted

Comment out this line, try your update again and you should be good to go.

Fixing Messenger when you've accidentally screwed it up

If you're like me, you like to have your Windows Live Messenger conversation windows be as simple and clean as possible, with no toolbars, and no contact pictures. To that end, I removed the toolbars from my messenger contact windows so that I wouldn't have to see them. However, this became a problem one day when I dragged a picture that I intended to send to someone into a conversation window, and instead of sending it to them, Messenger permanently changed the background of my chat windows with that person to that picture. To resolve this, I had to open a chat window with person X, press the Alt key to get the old-school windows standard toolbar to pop-up at the top, and then go to Tools -> Show toolbars -> Standard. Then from the standard toolbar, you can click on the 'Show Menu' button on the top right of the conversation window from the standard toolbar, and go to Tools -> Backgrounds ... . This wil take you to a screen where you can select a blank default background. However, dragging the picture may have changed the default background colour for the window, as it did in my case. To remedy this, you have to change the background colour to match the rest of the Messenger colour scheme, and you can do so by clicking on the paintbrush icon on the standard toolbar, and selecting a default background colour from there to make things consistent with the rest of the Messenger colour scheme.

How to recurlively delete a folder and its contents in PowerShell

The command :

Remove-Item -recurse -force [directory name]

The really sad thing is that I googled this and there are no sites that explicitly state how to do this. The comparable command in bash :

rm -rf [directory name]

Yet one more reason I hate Microsoft and PowerShell in particular.

RESTful web services with JAXB 2.0

In case you're not familiar, JAXB (Java API for Xml Binding) is an API developed by Sun for binding between XML and Java beans. The first incarnation, 1.x, was interface+implementation based like XMLBeans from the Apache Project. The second incarnation, 2.x, is annotation+pojo based. It's a very useful API, especially when combining it with Hibernate (and the Java Persistence API) to make restful web services. But, that's not really the point of this post. The point is that I've been using JAXB 2.0 for web services much in the past, but this is the first time where I've had to map the "class hierarchy per-table" pattern used by Hibernate into XML. As it turns out, JAXB 2 has very good support for this pattern. You can read more on this at the java.net project page for JAXB.

Logging for tests using the Spring Framework

It's been a while since I've posted to the blog 'cause I've been so busy, and it seems fitting that this be a good way to resume posting, as this issue has pissed me off quite a bit and been a major thorn in my side for the longest time.

The Spring Framework has some pretty good support for creating test classes for your application, however it by default does not properly initialize log4j logging when doing tests, and I found out today why. When running your application in a Servlet container, you'd configure Spring logging in web.xml. However, when running in a standalone context, Spring has no way of knowing how you want logging configured, so it leaves it up to log4j to configure itself. On that front, you have to realize what log4j's default configuration strategy is : reading a 'log4j.properties' file from the root of the classpath. Once this hits you (and it took me a while), getting logging running for your test cases becomes a simple matter of placing a valid 'log4j.properties' config file in the root of your test classpath, and logging starts working properly, so now you can read those pesky hibernate generated queries off your test log .

Determining which version of Ubuntu you're running

At our company, we use Ubuntu to run our servers. Sure, there's other distributions with potentially better performance, but none so easy to setup, and that was the deciding factor in choosing which distro was going to run our systems because I had to set it up, and since I'm both developer and system administrator (*very* small company), I really don't have time to fuck around and I need to make things as easy on myself as possible. To that end, I've decided to start writing tutorials on everything I learn how to do, and I needed to make sure I note which version of Ubuntu / Linux I'm using. To that end, in order to determine which version of Ubuntu you're running, run this :

cat /etc/issue

I learned of this little trick from here.

*Edit (2008-10-29)*
A much better command for determining the current Ubuntu version you're running :

lsb_release -a

More random MySQL glitches

I ran into the following exception recently when moving an application from one server to another :

java.lang.NullPointerException
 at com.mysql.jdbc.StringUtils.indexOfIgnoreCaseRespectQuotes(StringUtils.java:959)
 at com.mysql.jdbc.DatabaseMetaData.getCallStmtParameterTypes(DatabaseMetaData.java:1296)
 at com.mysql.jdbc.DatabaseMetaData.getProcedureColumns(DatabaseMetaData.java:3670)
 at com.mysql.jdbc.CallableStatement.determineParameterTypes(CallableStatement.java:702)
 at com.mysql.jdbc.CallableStatement.(CallableStatement.java:513)
 at com.mysql.jdbc.Connection.parseCallableStatement(Connection.java:4422)
 at com.mysql.jdbc.Connection.prepareCall(Connection.java:4496)
 at com.mysql.jdbc.Connection.prepareCall(Connection.java:4470)
 at org.apache.commons.dbcp.DelegatingConnection.prepareCall(DelegatingConnection.java:275)
 at org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.prepareCall(PoolingDataSource.java:292)

As it turns out, there was a permissions issue whereby the function was created with a line specifying the definer and this causes the 'SHOW CREATE FUNCTION' call to fail and return null unless the user calling the statement has permissions for select on the 'mysql' database. Some recommended solutions (that I didn't get around to trying) were changing the call to 'prepareStatement' as opposed to 'prepareCall'. The issue is logged as MySQL Bug #24065. Lately it just seems as if I keep hitting every bug out there, and can't get anything done. I hope this helps somebody.

Commons VFS (FTP) problems

I recently had a problem with Commons VFS whereby I could log into an FTP server and list the contents of the initial directory, but no contents were shown, nor could I otherwise resolve any of the contents or subdirectories. As it turns out, there's a problem with FTPClient which is part of the Commons Net package, and the basis for the FTP module of Commons VFS. After logging in, if the VFS client tries to set passive mode and the server doesn't respond that it allows passive mode (ie PureFTP specifically), then the client just continues as if there's no problem instead of throwing an Exception. The result was getting an error message like "The file root [ftp://myuser:*****@localhost/my_sub_folder] is not a folder". Since I wasn't able to get PureFTP successfully configured to allow passive mode, I was able to resolve the problem by forcing the code to use active mode instead. Fortunately this wasn't a problem since the FTP server in question was on the same machine as the code trying to access it (ie not across the boundary of a router).

Software developers are arrogant assholes

Like the title of this post says, software developers are arrogant assholes. I can say that because I am one. The reason I say this is that I've been Googling like a mofo for articles related to RESTful development and RESTful web services servers using Ruby on Rails, and I must say that it's a real pain in the ass. The vast majority of the articles I'm able to find are in blog format, and are (as is typical with blog-style articles / tutorials) very vague, and don't provide enough detail for a learner to get going. Essentially, they make the assumption that you already know something about Ruby on Rails, and it's a rather hypocritical assumption for a tutorial / article to make. I will admit that I've been somewhat guilty of doing this same thing in my own blog whenever I've provided code examples, so it stops now. Any future "tutorials" on this blog are going to be as complete as possible, time constraints at work be damned. Vagueness cannot be allowed to continue.

Setting up your own domain in (Ubuntu) Linux

...is easier than you actually think. I managed to get a working domain name for our company's servers going using tutorials and information collected from here, here, here and here.
I'd love to be able to write a coherent guide based off of the information from these pages, but I'm just too busy at work to do it at the moment.

A Quick note on SFTP jails

SFTP jails are uber useful and I've blogged about them before, but one crucial piece of information that I've been missing has been where it all started. This thread on the Ubuntu forums was the base for all of the work that I've done and it has made it super easy to setup jails here at work, which is a blessing due to the frequency with which we move files and make changes. I'm finding more and more that I owe an increasing amount of thanks to the people and posts on forums, both Ubuntu and others, so thanks.

Understanding Linux ACLs

Ok, so for a while, I've had an SFTP jail setup within our company for our clients to connect and dump batch files to our systems. It later became necessary to have an administrator user for our staff to be able to go in and read any of the files from any of the clients without having to use a bunch of different logins to login as each individual client. This makes sense as doing so would be far too cumbersome. This is where ACLs came in. I learned what I had to so that I could get going, but that wasn't very much (forunately at the time, unfortunately later). I've since learned a couple of interesting things since then:

There are two types of ACLs in Linux :

1. The access ACL which controls access to files and directories


2. The default ACL which applies to directories only and acts like a template for newly created files and subdirectories within that directory.

The former I knew about right from the beginning (pretty obvious), but I didn't really know the proper name for what I was manipulating. The latter I learned about today, and had previously assumed that Access and Default ACLs were one and the same (I didn't know about the distinction because it wasn't mentioned in the fucking

man

page.

Today's karmic balance

It's pretty rare that I have something to blog about within a couple days of each other, never mind on the same day, so I suppose that this post is the karmic balance of the other for today. I just found out yesterday that because one of our processing partners had their douchebag of a contractor ditch on them, I now have to maintain two systems and integrate them both together. That in and of itself is kinda stupid. But at least this'll be my first production interaction with Ruby on Rails, and I'm actually really looking forward to the experience. I've been meaning to get myself up to speed with Rails, but between feeling tired after I get home and working so damn much that I don't have the time when I get home, I haven't really had the chance. It's going to be an interesting coming couple of weeks.

Use DTDs, they're there for a reason

<rant>
As the title of this post states, if you're a web developer, use a fucking DTD. They exist for a reason, that reason being to allow web browsers to have a reasonable expectation of the content and layout of your website so they can deliver the desired experience to your user. If you're a web developer and you don't know what a DTD is, then you're in serious fucking trouble. In the event that you don't know, DTD stands for Document Type Definition, and it's a single line of XML that goes at the very beginning of HTML documents and almost at the very beginning of XML documents (if they're validated by DTDs). An example of a DTD :

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

That DTD is for a strictly validated XHTML 1.0 compliant HTML document. This means that it's strongly validated and web browsers can expect everything after it to be well-formed quality. That's right bitches, I use a good version of HTML and I'm standards compliant like a mofo.
</rant>

Sorry, but I just had to get that out. Lately, I'm being inundated with pages from our partners that don't use DTDs, don't validate to anything, and are just generally horrible markup. Now, normally, a person wouldn't need to care, but when your partners are lame and you have to scrape their pages for data, the lack of developing to a DTD becomes a giant pain in the ass.

A letter to Apple

Yes, these things are cliche, but whatever, screw it.

Dear Apple,

In case you haven't figured it out from my buying patterns, I've stopped buying music from you that isn't DRM-free. This is because, as Steve Jobs has admitted himself, DRM is archaic, and frankly doesn't work. What your company doesn't seem to realize is that if you want to continue your high level of sales, (especially to technophiles / audiophiles such as myself) you're going to need to get going on casting off the DRM that exists on your considerable library of music. I steadfastly refuse to purchase any music that is not DRM-free. I want to be able to play it anywhere on whatever device I may happen to own, and I'm not going to cave into unreasonable demands of an already clearly greedy music industry that refuses to evolve and adapt to technological reality. If I can't purchase music through large corporations such as yourself, I'm going to look elsewhere : smaller sites, independent labels, and independent artists who publish their music for free. So, until you get your head out of your ass : screw you, you're not getting one thin dime from my pocket.

Beginning with SQL Server

Given changes in the environment in which our business does it's business, I've had to start learning to use SQL Server and various other Microsoft technologies lately. A quick note on connecting to a foreign SQL Server instance (ie another company's ...) :

Create an alias for the database so that Enterprise Manager has something to work with

Open up the Client Network Utility which should be included in the Start menu programs group for your SQL Server installation.

Start -> Programs -> Microsoft SQL Server -> Client Network Utility -> Alias (tab) -> Add... (button).

Under 'Server alias' enter an easy to remember name for the connection. Under 'Network libraries' select the TCP/IP option. Under 'Connection parameters' enter the DNS name or IP address under 'Server name' of the server you wish to connect to. Change the option for 'Dynamically determine port' if the server you're attempting to connect to doesn't run under the standard port of 1433 for SQL Server. Hit 'Ok' to save your settings, then 'Ok' to close out of the Client Network Utility.

Create a new SQL Server Registration to add your SQL Server instance to the Enterprise Manager

Open Enterprise Manager. It should be in the same programs group in the start menu as the Client Network Utility. Once open, create a new SQL Server Group if you haven't already got one (or haven't got one that you want to add your new SQL Server instance to). Then add a new SQL Server Registration. You should be prompted by a Wizard at this point. (If you're not, then you've probably already disabled the Wizard and don't need to be reading this tutorial.) In the wizard, click on 'Next' to proceed to the SQL Server selection screen. Under the list of available servers, you should see the alias you just created in the previous step. Select it and click on 'Add >' to add it to the list of added servers, and then click on 'Next'. After this, you should be prompted for credentials, and the rest is pretty self explanatory.

Cool MySQL tricks

It's been a while since I've written a blog post, and I figured this was a good topic to write about. For the most part, I don't use SQL. There's numerous ORM (Object-Relational Mapping) tools and frameworks out there (ie Hibernate) that abstract away all the boiler-plate CRUD code. When I do have to use SQL (be it on the command line or with a query browser), I'm not afraid to dive right in, and it's interesting to learn new things about SQL because there's so much to learn and it's such a ridiculously powerful query language.

I had to update the configuration in one of my databases, but the configuration required inserting numerous new lines into a table for user roles. I could've written a stored procedure to do it, but given my (admittedly somewhat limited) knowledge of SQL, I figured this would take too much time and I didn't want to do it. (This is what I like to call constructive laziness). I kept Googling and found MySQL's INSERT INTO ... SELECT syntax, which allows you to conveniently insert the results of one query into another table. I'm sure that most other database implementations out there have a similar convenience syntax, but I happen to work with MySQL so there you go. It took what would've been a numerous line script with looping and separate SELECT and INSERT statements down to a one liner. If you use MySQL (especially with LAMP / AJAX) I recommend that you read about it.

Deleting .svn folders

Subversion is a great tool, but unfortunately it has to store metadata somewhere, and like all other code repository tools, it stores them in metadata directories ... for each directory in whatever project you're working with. I recently found that I have to copy parts of my project documentation out for some of our clients to access our APIs, and I wanted to quickly delete all the SVN metadata and trim certain other files where necessary. I figured the quickest way to do with would be a simple command. Windows PowerShell provides a good (though not great, and certainly not as good as bash) way of doing it :

Get-ChildItem -Recurse -force |where {$_.PSIsContainer -AND $_.Name -match "svn"} | foreach ($_) {remove-item -force -recurse $_.fullname}

Two Google queries yielded the above command from this blog. Happy reading.