How to automate a build of a Java class and all the classes it depends on?

Question

I guess this is kind of a follow-on to question 1522329.

That question talked about getting a list of all classes used at runtime via the java -verbose:class option.

What I'm interested in is automating the build of a JAR file which contains my class(es), and all other classes they rely on. Typically, this would be where I am using code from some third party open source product's "client logic" but they haven't provided a clean set of client API objects. Their complete set of code goes server-side, but I only need the necessary client bits.

This would seem a common issue but I haven't seen anything (e.g. in Eclipse) which helps with this. Am I missing something?

Of course I can still do it manually by: biting the bullet and including all the third-party code in a massive JAR (offending my purist sensibilities) / source walkthrough / trial and error / -verbose:class type stuff (but the latter wouldn't work where, say, my code runs as part of a J2EE servlet, and thus I only want to see this for a given Tomcat webapp and, ideally, only for classes related to my classes therein).

Answer 1

I would recommend using a build system such as Ant or Maven. Maven is designed with Java in mind, and is what I use pretty much exclusively. You can even have Maven assemble (using the assembly plugin) all of the dependent classes into one large jar file, so you don't have to worry about dependencies.

http://maven.apache.org/

Edit:

Regarding the servlet, you can also define which dependencies you want packaged up with your jar, and if you are making a stand alone application you can have the jar tool make an executable jar.

note: yes, I am a bit of a Maven advocate, as it has made the project I work on much easier. No I do not work on the project personally. :)

Answer 2

What you want is not only to include the classes you rely on but also the classes, the classes you rely on, rely on. And so on, and so forth.

So that's not really a build problem, but more a dependency one. To answer your question, you can either solve this with Maven (apparently) or Ant + Ivy.

I work with Ivy and I sometimes build "ueber-jar" using the zipgroupfileset functionality of the Ant Jar task. Not very elegant would say some, but it's done in 10 seconds :-)