How to weave aspects using AspectjCompile task

[libertywork-agb]

I am using the io.freefair.aspectj.base plugin version 6.3.0. Referencing the documentation, it can be used in this way:

task myAjcTask(type: io.freefair.gradle.plugins.aspectj.AspectjCompile) {
    aspectjClasspath.setFrom configurations.aspectj
    ajcOptions {
        inpath = files()
        aspectpath = files()
    }
}

I created an aspectj configuration (it did not exist from applying the plugin), declared a dependency to the subproject containing my aspects using that configuration, defined my custom ajc task, and finalized compileJava by my ajc task.

plugins {
    id 'java'
    id 'io.freefair.aspectj.base' version '6.3.0'
}

configurations {
    aspectj
}

dependencies {
    aspectj project(':my-aspect-lib')
}

task myAjcTask(type: io.freefair.gradle.plugins.aspectj.AspectjCompile) {
    aspectjClasspath.setFrom configurations.aspectj
    ajcOptions {
        inpath.setFrom compileJava.outputs.files
        aspectpath.setFrom configurations.aspectj
    }
}

compileJava.finalizedBy tasks.myAjcTask

This setup results in the following exception when running compileJava:

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':html-sanitizer-test:myAjcTask'.
Caused by: java.lang.NullPointerException
	at io.freefair.gradle.plugins.aspectj.internal.AspectJRuntime.findAspectjtoolsJarFile(AspectJRuntime.java:108)
	at io.freefair.gradle.plugins.aspectj.internal.AspectJRuntime.access$000(AspectJRuntime.java:28)
	at io.freefair.gradle.plugins.aspectj.internal.AspectJRuntime$1.inferAspectjClasspath(AspectJRuntime.java:67)
	at io.freefair.gradle.plugins.aspectj.internal.AspectJRuntime$1.createDelegate(AspectJRuntime.java:59)

aspectjClasspath does not have much in the way of documentation, so I don't really understand its importance, but it seems like I have it set correctly based on the example myAjcTask from the documentation. My problem is that I don't know exactly what to put for inpath and aspectpath.

From my understanding, inpath should be the files into which aspects are woven and aspectpath should be the files containing the aspects to weave. I want the compiled Java to be woven with my-aspect-lib aspects.

If I just don't set inpath or if I set it to an empty file collection (files()) then running the build succeeds but of course it doesn't weave any aspects.

I also tried upgrading to version 6.4.1 of the plugin and got the exact same results.

Why am I getting this exception and how should inpath and aspectpath be configured?

[larsgrefer]

You are basically doing, what the io.freefair.aspectj.post-compile-weaving does.

From my understanding, inpath should be the files into which aspects are woven and aspectpath should be the files containing the aspects to weave. I want the compiled Java to be woven with my-aspect-lib aspects.

That is correct.
aspectjClasspath should contain the aspectj compiler itself.

The io.freefair.aspectj.base plugin tries to infer the ajc version based on the classpath of the corresponding compile task, but this fails here because the compile classpath is null.

[libertywork-agb]

I understand that io.freefair.aspectj.post-compile-weaving does basically the same thing, but in my other discussion Q&A post you indicated that it was not possible to exclude specific project classes from being processed. I need a Gradle plugin that can weave only certain aspects and exclude project aspects.

I'm afraid I don't quite understand what you mean by compile classpath.

If I add these lines to my task:

println 'compileJava.outputs.files: ' + compileJava.outputs.files
compileJava.outputs.files.forEach(file -> println file)

I get this output:

compileJava.outputs.files: task 'compileJava' output files
/home/user/projects/root-project/consuming-subproject/build/classes/java/main
/home/user/projects/root-project/consuming-subproject/build/generated/sources/annotationProcessor/java/main
/home/user/projects/root-project/consuming-subproject/build/generated/sources/headers/java/main
/home/user/projects/root-project/consuming-subproject/build/tmp/compileJava/previous-compilation-data.bin

If I add these lines to my task:

println 'configurations.aspectj: ' + configurations.aspectj
configurations.aspectj.forEach(file -> println file)

I get this output:

configurations.aspectj: configuration ':consuming-subproject:aspectj'
/home/user/projects/root-project/my-aspect-lib/build/libs/my-aspect-lib-0.0.1.jar
/home/user/.gradle/caches/modules-2/files-2.1/org.aspectj/aspectjrt/1.9.7/ha5h/aspectjrt-1.9.7.jar
...

If I add any of the following dependencies I still get the same exception:

compileClasspath 'org.aspectj:aspectjrt:1.9.7'
compileClasspath 'org.aspectj:aspectjweaver:1.9.7'
compileClasspath 'org.aspectj:aspectjtools:1.9.7'

How can the compile classpath be set, and how can it be ensured that the AspectJ classpath contains the AspectJ compiler?

[larsgrefer]

I've made some changes to the plugin which should make your use-case a bit easier (and the error message less confusing).

The io.freefair.gradle.plugins.aspectj.AspectjCompile task has four properties that are relevant here:

• aspectjClasspath: This file collection must contain the aspectjtools.jar and will be used to actually invoke the ajc compiler.
• classpath: This file collection will be directly mapped to the -classpath argument of ajc. When using the io.freefair.aspectj.base plugin, this defaults to null. When using the other plugins it should be correctly wired to use the compileClasspath configuration.
• ajcOptions.inpath: This file collection will be mapped to the -inpath argument of ajc
• ajcOptions.aspectpath: This file collection will be mapped to the -aspectpath argument of ajc.

More information about the ajc arguments can be found here: https://www.eclipse.org/aspectj/doc/released/devguide/ajc-ref.html

In its current form, the base plugin tries to determine the aspectjtools.jar for the aspectjClasspath by inspecting the classpath.
For the other plugins this works well, but in your case it failed, because classpath was null.

With my changes, which will be available with the next release, the plugin will inspect both the classpath and the ajcOptions.aspectpath to find the correct ajc version. This should work for you, since your aspectpath contains a aspectjrt.jar