How do I set the Eclipse build path and class path from an Ant build file?

Question

Hey folks,

There's a lot of discussion about Ant and Eclipse, but no previously answered seems to help me.

Here's the deal: I am trying to build a Java program that compiles successfully with Ant from the command-line. (To confuse matters further, the program I am attempting to compile is Ant itself.)

What I really want to do is to bring this project into Eclipse and have it compile in Eclipse such that the type bindings and variable bindings (nomenclature from Eclipse JDT) are correctly resolved. I need this because I need to run a static analysis on the code that is built on top of Eclipse JDT. The normal way I bring a Java project into Eclipse so that Eclipse will build it and resolve all the bindings is to just import the source directories into a Java project, and then tell it to use the src/main/ directory as a "source directory."

Unfortunately, doing that with Ant causes the build to fail with numerous compile errors. It seems to me that the Ant build file is setting up the class path and build path correctly (possibly by excluding certain source files) and Eclipse does not have this information.

Is there any way to take the class path & build path information embedded in an Ant build file, and given that information to Eclipse to put in its .project and .classpath files? I've tried, creating a new project from an existing build file (an option in the File menu) but this does not help. The project still has the same compile errors.

Thanks, Nels

Answer 1

I've never found a really clean way to do it, but one "hackish" way to do it is to manipulate the .classpath file eclipse uses (this contains the build path).

So the .classpath is going to have stuff in it like this:

<classpathentry kind="lib" path="C:/jboss-4.2.3.GA/client/jboss-system-client.jar"/>

So you could, for example, write some sort of batch script, etc. which would read your ant file dependencies and put them into the eclipse .classpath file (in the proper format, of course).

But personally, I never fool with such things. What I do is just put all the jars my project needs in one folder, and then in my ant file I have a path set up like this:

<path id="all_libs">
    <fileset dir="test_reflib">
        <include name="**/*.jar"/>
    </fileset>
</path>

test_reflib just needs to be defined to wherever this folder is that contains all the jars.

Then, on the eclipse side you can just do a "Add jars" and navigate to this same folder and just pick all the jars. What's even cooler is that any time you drop new jars into this folder, just click at the root level in the eclipse project and do "Refresh", and then edit the build path and click add jar again and it will only show you the jars that you haven't already added to the build path yet (i.e. the new jar you just dropped into the folder).

This obviously doesn't work too well if you are sharing jars in a central place, but it works pretty well for smaller projects where you can just copy all the jars over to a centralized folder for the project.

Answer 2

From the raw ant distribution, first run "ant -f fetch.xml" (or similar) to download a lot of needed dependencies. Add these to your Eclipse project and see if it helps.

Answer 3

We've generated Ecipse .classpath and .project files from Ant for a large project with centrally located jars (100+) (not counting src jars and javadocs). Similar to the build.xml linked from here http://people.csail.mit.edu/stefie10/antAndEclipse.html with the obvious addition of the src and javadoc attributes.

Answer 4

I use the ivy to manage my ANT classpaths, I highly recommend learning how it works.

There is an eclipse plugin that will manage the eclipse classpath from the same ivy.xml file that ANT uses to define it's dependencies.