How to programmatically exclude top level packages from src/java in gradle?

Question

I have a project that has about 100 top level packages. I want to be able to make a jar for some of these top level packages. The code below finds the top level packages, but how do I actually do the exclusions so i only get one?

It would be nice to generalize this so that it could work with packages that are not at the top level.

sourceSets {
    List<String> folders=new LinkedList<>()
    String target="r"
    for(String path:main.java.srcDirs) 
        for(String name:new File(path).list())
            if(!name.equals(target))
                if(new File(path,name).isDirectory()) 
                    folders.add(name)
    println("how to exclude these folders: "+folders)
    
}

Answer 1

In an empty directory you can create a simulation of your source setup with the following script:

def dir = new File('src/main/java')

['a', 'b', 'c', 'd', 'e'].each { l1 -> 
  ['x', 'y', 'z', 'r', 'v'].each { l2 -> 
    def f = new File(dir, "$l1/$l2/SampleClass.java")
    f.parentFile.mkdirs()
    f.text = """\
      package ${l1}.${l2};

      class SampleClass { 

      }
    """.stripIndent()
  }
}

which, when run, generates the following:

─➤ groovy write.groovy 

─➤ find src/main/java -type f | sort
src/main/java/a/r/SampleClass.java
src/main/java/a/v/SampleClass.java
src/main/java/a/x/SampleClass.java
src/main/java/a/y/SampleClass.java
src/main/java/a/z/SampleClass.java
src/main/java/b/r/SampleClass.java
src/main/java/b/v/SampleClass.java
src/main/java/b/x/SampleClass.java
src/main/java/b/y/SampleClass.java
src/main/java/b/z/SampleClass.java
src/main/java/c/r/SampleClass.java
src/main/java/c/v/SampleClass.java
src/main/java/c/x/SampleClass.java
src/main/java/c/y/SampleClass.java
src/main/java/c/z/SampleClass.java
src/main/java/d/r/SampleClass.java
src/main/java/d/v/SampleClass.java
src/main/java/d/x/SampleClass.java
src/main/java/d/y/SampleClass.java
src/main/java/d/z/SampleClass.java
src/main/java/e/r/SampleClass.java
src/main/java/e/v/SampleClass.java
src/main/java/e/x/SampleClass.java
src/main/java/e/y/SampleClass.java
src/main/java/e/z/SampleClass.java

─➤ 

With the following build.gradle in the root of this directory tree:

apply plugin: 'java'

task jara(type: Jar) {
  archiveBaseName = 'jara'
  from jar.source
  include 'a/**/*'
}

task jarb(type: Jar) {
  archiveBaseName = 'jarb'
  from jar.source
  include 'b/**/*'
}

artifacts {
  archives jara, jarb
}

you can then run:

─➤ gradle clean build 

BUILD SUCCESSFUL in 509ms

which generates:

─➤ ls -1 build/libs
groovy-how-to-programmatically-exclude-top-level-packages-from-src-java-in-gradle.jar
jara.jar
jarb.jar

─➤ unzip -l build/libs/jara.jar    
Archive:  build/libs/jara.jar
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  2020-12-21 15:56   META-INF/
       25  2020-12-21 15:56   META-INF/MANIFEST.MF
        0  2020-12-21 15:56   a/
        0  2020-12-21 15:56   a/r/
      266  2020-12-21 15:56   a/r/SampleClass.class
        0  2020-12-21 15:56   a/y/
      266  2020-12-21 15:56   a/y/SampleClass.class
        0  2020-12-21 15:56   a/z/
      266  2020-12-21 15:56   a/z/SampleClass.class
        0  2020-12-21 15:56   a/x/
      266  2020-12-21 15:56   a/x/SampleClass.class
        0  2020-12-21 15:56   a/v/
      266  2020-12-21 15:56   a/v/SampleClass.class
---------                     -------
     1355                     13 files

─➤ unzip -l build/libs/jarb.jar
Archive:  build/libs/jarb.jar
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  2020-12-21 15:56   META-INF/
       25  2020-12-21 15:56   META-INF/MANIFEST.MF
        0  2020-12-21 15:56   b/
        0  2020-12-21 15:56   b/r/
      266  2020-12-21 15:56   b/r/SampleClass.class
        0  2020-12-21 15:56   b/y/
      266  2020-12-21 15:56   b/y/SampleClass.class
        0  2020-12-21 15:56   b/z/
      266  2020-12-21 15:56   b/z/SampleClass.class
        0  2020-12-21 15:56   b/x/
      266  2020-12-21 15:56   b/x/SampleClass.class
        0  2020-12-21 15:56   b/v/
      266  2020-12-21 15:56   b/v/SampleClass.class
---------                     -------
     1355                     13 files

─➤ 

ie two jar files, one with all the classes from the a top level package, one with all the classes from the b top level package.

Not sure if this hits your target square on, but it should give you some idea of how to accomplish what you want.