Question

How do you debug java annotation processors using intellij?

Preferably using IDEA IntelliJ. I tried setting a breakpoint inside the processor and running but it did not break.

Answer 1

If you really need to debug an annotation processor, it might be better to run the annotation processor from the command line rather than within your IDE with debugging enabled and attach to that using your IDE's debugger.

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If running javac directly, you can debug this by specifying the following extra parameters:

javac -J-Xdebug -J-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000 ... (usual javac parameters go here)

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If running Maven, use mvndebug instead of the standard mvn command - Maven runs the compiler in-process.

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If running Ant, add the following to the ANT_OPTS environment variable before running:

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

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With all these executions, the javac, Ant or Maven process will wait for you to attach your debugger before it actually starts executing. IntelliJ instructions for this are here. For Eclipse, here.