In my annotation processor, I wanted to locate a file in source path, so I wrote the following code:

FileObject fo = processingEnv.getFiler().getResource(StandardLocation.SOURCE_PATH, "", "META-INF/persistence.xml");

It throws NullPointerException if I do not specify -sourcepath option while invoking javac. I have two questions:

1) Is "." not the default value for source search path?

2) Instead of throwing an IOException as per the javadocs of getResource, why is it throwing an NPE?

The stack trace is:
java.lang.NullPointerException
at com.sun.tools.javac.util.DefaultFileManager.getFileForOutput(DefaultFileManager.java:974)
at com.sun.tools.javac.util.DefaultFileManager.getFileForOutput(DefaultFileManager.java:950)
at com.sun.tools.javac.processing.JavacFiler.getResource(JavacFiler.java:434)
at foo.Ap.readDD(Ap.java:182)
at foo.Ap.init(Ap.java:101)
at com.sun.tools.javac.processing.JavacProcessingEnvironment$ProcessorState.<init>(JavacProcessingEnvironment.java:339)
...

Sahoo

 

 

Sahoo,

This looks like a bug to me.

Despite the fact that it shouldn't throw an NPE, are you sure the file exists in your SOURCE_PATH?

I have read your blog, and it would seem to me that if you are generating the META-INF/persistence.xml file, then if that has already been done, it ought to be in CLASS_OUTPUT (that is the location where I put generated service lookup files).

Also, you might like to take a look at the hickory project on java.net which has a couple of things that could simplify your code.

First there is a class to handle collecting state and maintaining it over multiple incremental compiles. This would enable your processor to work correctly when you remove an annotation from a single class, and just recompile that one class. I am not sure if your existing code can correctly rebuild the persistence.xml file in that case, but hickory's StateSaver takes most of the pain away from those situations where a single output class or resource is derives from multiple source files.

You may also be interested in the prisms mechanism that makes handling known annotations much easier. It gives the best of both worlds between getting the runtime annotation via Element.getAnnotation(Class<A> annotationType)
and using AnnotationMirrors.

Also there is a package there designed to support testing annotation processors which you might find useful.

https://hickory.dev.java.net/nonav/apidocs/index.html

Bruce

 

 

Bruce,

Yes, the file does not exist in default sourcepath, ".", yet I get NPE if I don't specify -sourcepath.

I plan to do some more work on annotation processing, so I will take a look at the hickory project, it does sound interesting. I am not answering questions specific to the annotation processor here as they can be distracting to someone following this thread. If you ask them in my blog, I can answer them.


Thanks,
Sahoo

 

 

I've filed Sun bug 6647998 to track this issue.