So you want a web project, a build system and a reasonable IDE to take care of the annoying details for you, right? The good news are that it's actually quite possible and there're many ways to do this. The bad news are that it's nigh impossible to get them to play along if you don't already know how to do that. It took me days to find a solution that finally seems to work, and I'd like to share it with you. I'm probably missing a few important details or did something really really stupid along the way (I'd appreciate comments!), but this process does seem to work. I'm not going into essentials of Java-based web development here -- if you want a more basic explanation of the terminology, post a comment and I'll see what I can do...
I want to:
- Use a common, standard and powerful IDE to edit and debug my Java code, and preferably provide a usable GUI interface for dependency and project management;
- Use a common, standard servlet container to host my servlet and still be able to control and debug everything from the same IDE;
- Have a convenient way to handle internal-and-external dependencies without worrying too much about the details;
- Be able to quickly compile, test and package my servlet for deployment;
- Understand as little as possible about the dependency stack of the tools involved
I'm going to tell you how to achieve most of these goals, with two glaring omissions: I won't show you how to do testing (I haven't successfully managed servlet unit testing so far -- different post on that) and I can't help but delve into some of the more annoying details involved with these tools and their dependencies. Sorry about that. Additionally, some of the information here applies even if you use different tools, but you're bound to face issues not covered here; don't assume I know more than you do -- seek the answers, post them somewhere, and maybe the next person will actually find what they're looking for!
The tools used are:
- J2SE JDK is an obvious must-have. Version used: JDK 6 update 3;
- Eclipse (but please don't download it just yet) for code editing, debugging and project management;
- Web Tools Platform: this is the Eclipse plug-in that adds web development capabilities to the IDE, including J2EE dependency management, hosting and running servlets from within the Eclipse workspace etc. This would be a good time to run along to the WTP web-site and download the Web Tools Platform All-In-One package. I only used the release version (2.0.1 at the time of writing this), so if you use another version your mileage may vary;
- Apache Maven is the newfangled build system from Apache slated to replace ant. I've used it for the last few days and so far it appears to be quite robust and even fairly well-integrated into Eclipse (see next item). Version used: 2.0.8;
- M2eclipse is the Eclipse plug-in for Maven integration. I've only found one problem with it so far, which I'll detail later on;
- Apache Tomcat is a solid choice in servlet containers. It's robust, fast and open-source, and has terrific Eclipse integration. I haven't given any of the other containers a serious whirl yet though.
Unlike Visual Studio, with the tools mentioned above there's no straightforward installation procedure. You'll have to designate at least a workspace directory (where your Eclipse projects, settings etc. go) and some location where the tools themselves go. For me, it's C:\Dev\Eclipse and C:\Tools respectively.
- Setting up Java:
- Install the JDK and remember where it was installed (nominally in %PROGRAMFILES%\Java\jdk1.6.0_03)
- Set up a system-wide JAVA_HOME environment variable pointing to the same directory
- Setting up Maven and Tomcat:
- Extract both archives to your designated directory (e.g. for Maven it would be C:\Tools\apache-maven-2.0.8)
- Add the Maven bin directory to your PATH environment variable (user- or system-wide, depending on your preference)
- Add whichever J2EE libraries you desire from the Tomcat installation to your class-path. If you have no idea what I'm talking about, you'll probably just want to set the CLASSPATH environment variable to your equivalent of c:\tools\apache-tomcat-6.0.14\lib\servlet-api.jar;c:\tools\apache-tomcat-6.0.14\lib\jsp-api.jar
- Setting up Eclipse:
- Extract the WTP all-in-one package (which contains Eclipse itself) to your designated directory (e.g. C:\Tools\Eclipse)
- Load Eclipse and point it to your designated workspace location
- Install M2Eclipse:
- Go to Help->Software Updates->Find and Install..., select "Search for new features to install" and click Next
- Click on New Remote Site..., use M2eclipse or whatever for the name and http://m2eclipse.codehaus.org/update/ for the URL
- Click on Finish and let Eclipse install the M2Eclipse plug-in
- Set up a web server runtime for Eclipse to host your servlets in:
- Open Window->Preferences...
- Under Server select Installed Runtimes and click on Add...
- Choose (from Apache) the Apache Tomcat v6.0 runtime and click Next
- Enter the Apache installation directory (e.g. C:\Tools\apache-tomcat-6.0.14) in the appropriate location and click Finish
4. Creating a new web project
First off, you must create the actual project, directory structure etc. To do this:
- Open a command prompt, go to your Eclipse workspace directory
- Decide on your Maven group and artifact IDs; it's worth noting that the artifact ID is also the directory name for the project
- Type in mvn archetype:create -DgroupId=your.group.id -DartifactId=your.artifact.id -DarchetypeArtifactId=maven-archetype-webapp
- You'll notice that a new directory was created under the workspace root
- Edit the Maven project descriptor POM.XML in the newly created directory:
- Add (after the <url> tag, although I'm not sure the order matters) the following section:
- Under <build>, add the following section:
- You can now thank my colleague Aviran Mordo for finding out this bit of Voodoo.
- In the command prompt, now enter the project directory
- Type in mvn eclipse:m2eclipse -Dwtpversion=1.5 to create an Eclipse project
- Run Eclipse if it's not already started, then from the package explorer right click anywhere and click on Import...
- Choose General->Existing Projects into Workspace. For root directory pick the workspace directory
- Choose the new project and click on Finish
- At this point you may encounter a "Java compiler level does not match the version of the installed Java project facet" error. If that's the case, just right-click on the error (in the Problems view) and select Quick Fix, which will allow you to change the Java project facet version to 6.0. If this isn't what you want, you probably know enough to resolve the issue on your own...
- You'll need a src/main/java directory as a root source folder (as per the Maven convention). Right-click on the project, select New->Source Folder and type in src/main/java.
- Finally, in order to execute or debug the project on an actual running server, right-click on the new project and select Properties. From there go to the Server tab and select the runtime you created in the previous chapter.
At this point you have a Maven web project with a corresponding Eclipse project ready for editing in your workspace. In practice you will have to do several things to have any meaningful results.
- Add your own code into the mix, such as a servlet. When adding a new servlet (via right-clicking the project, New->Other and choosing Web->Servlet) your WEB.XML file is automatically updated with the new servlet.
- Add your own dependencies. Maven handles dependencies quite well; for instance, in order to actually create a servlet you're going to need servlet-api.jar in your classpath; the easiest way to do this is to right-click the project, select Maven->Add Dependency and then simply type in servlet and choose javax.servlet servlet-api.
- When you wish to run or debug your servlet, right-click on its Java file and select Run As->Run on Server (or Debug, as appropriate). Your applet should be happily up and running.
5. Converting an existing project to Maven
I'm not sure how to go about doing this for web projects, but converting regular projects to use Maven is actually pretty straightforward; move your sources to the appropriate directories according to the Maven conventions, right-click the project in Eclipse and choose Maven->Enable Dependency Management; this will implicitly create a Maven project descriptor for you (POM.XML) and that's pretty much it. From that point on your Eclipse and Maven projects should peacefully coexist, allowing you to leverage both tools for your purposes.