Debugging Annotation processors in eclipse

Question

I am writing a simple annotation processor and trying to debug it using eclipse. I created a new project for annotation processor and configured javax.annotation.processing.Processor under META-INF as needed and it processes annotations fine.

Then, I added some more code and tried debugging, but could never make the execution stop at the breakpoints added in the annotation processor. I am compiling using ant and I am using the following ANT options.

export ANT_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000"

After triggering ant build, i go create a remote debug configuration and the debugger starts fine. Ant build also starts successfully. But the execution never stops at any break point added in the annotation processor.

Answer 1

This is a problem I just ran into, and the eclipse plugin solution seems super cumbersome to me. I found a simpler solution using javax.tools.JavaCompiler to invoke the compilation process. Using the code below, you can just Right-Click > Debug As > JUnit Test in eclipse and debug you annotation processor directly from there

   @Test
   public void runAnnoationProcessor() throws Exception {
      String source = "my.project/src";

      Iterable<JavaFileObject> files = getSourceFiles(source);

      JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

      CompilationTask task = compiler.getTask(new PrintWriter(System.out), null, null, null, null, files);
      task.setProcessors(Arrays.asList(new MyAnnotationProcessorClass()));

      task.call();
   }

   private Iterable<JavaFileObject> getSourceFiles(String p_path) throws Exception {
     JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
     StandardJavaFileManager files = compiler.getStandardFileManager(null, null, null);

     files.setLocation(StandardLocation.SOURCE_PATH, Arrays.asList(new File(p_path)));

     Set<Kind> fileKinds = Collections.singleton(Kind.SOURCE);
     return files.list(StandardLocation.SOURCE_PATH, "", fileKinds, true);
   }