Saturday, April 21, 2007

How to make Eclipse, Tomcat, Maven 2 and Wicket play nice

On the off chance that other people find this helpful, here's how I set up Tally-Ho to work in Eclipse with the Sysdeo Tomcat plugin and Maven 2.

First, obviously, you need to install your prerequisites. Download and install Tomcat. Install the Sysdeo Tomcat plugin. You also want the Maven 2 Eclipse plugin. Installation of these is outside the scope of this post. It is also outside the scope of this post to explain Maven, Tomcat, Servlets and so-on. Use Google.

Next, bootstrap your project. I found it easiest to change into my Eclipse workspace directory, use mvn to create my archetype for my project, and then run mvn eclipse:eclipse inside the project directory it created. Then go to File | Import in Eclipse and import the project. Finally, enable the Maven 2 plugin for your imported project from the project's context menu, Maven 2 | Enable.

I found that the only way to make working with Maven bearable was to follow its default layout. This means that web.xml is going in src/main/webapp/WEB-INF and that all of the library dependencies are defined in pom.xml and all of the libraries will download into the Maven 2 Dependencies collection the first time you run mvn on the project.

Edit pom.xml and make sure you have your dependencies defined how you want them and that your project name and version are what you'd like.

Now is a good time to run a build of the project just to set up all of the remaining directories, like target. I did this by configuring an m2 build from the External Tools menu using my project's location as the Base directory with the goal "install".

Now set up the Tomcat plugin. From Window | Preferences | Tomcat, configure the appropriate Tomcat version and Tomcat home. From the context menu of your project, select Properties and then Tomcat. Check "is a Tomcat project." Set the context name to "/" and check "Can update context definition" and "Mark this context as reloadable." Set the subdirectory to "/target/your_project_name-your.project.version". The project name and version here must match what you've defined in pom.xml.

Now set up Eclipse to build directly to the Maven output directory. This allows you to avoid running a mvn build every time you make a change to a class or resource file. You will still need to run a mvn build if you add or change dependencies or if you change web.xml, however. From the project's properties context menu, choose Java Build Path and set the default output folder to target/your_project_name-your.project.version/WEB-INF/classes.

Lastly, from your project's context menu, choose Tomcat Project | Update Context Definition.

So to recap, here are the steps:

1. Download and install Maven 2, Eclipse, Tomcat, the Maven 2 plugin for Eclipse and the Tomcat plugin for Eclipse.
2. Create a project using Maven. Consult Maven's documentation for more detail or use an existing project that already has a pom.xml.
3. Run mvn eclipse:eclipse to generate Eclipse's metadata files from the project's pom.xml.
4. Import the project into your Eclipse workspace.
5. Edit pom.xml to define the version number and your dependencies.
6. Put web.xml in src/main/webapp/WEB-INF
7. Create a m2 external build and run it to create your target directory structure.
8. Configure the Tomcat plugin to look in Maven's target directory for your webapp's directory structure.
9. Configure Eclipse to build directly to Maven's target directory structure.

To make the setup play nicely with Wicket, you only need to define Wicket as a dependency in pom.xml (step 5). This is a matter of adding:


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