Get callers method (java.lang.reflect.Method)

java, reflection

Solution

If it's just for testing, then this may work. It assumes that the class files are accessible via the calling class's `ClassLoader` and that the class files were compiled with debugging symbols (which I hope they are for testing!). This code relies on the ASM bytecode library.

public static Method getMethod(final StackTraceElement stackTraceElement) throws Exception {
    final String stackTraceClassName = stackTraceElement.getClassName();
    final String stackTraceMethodName = stackTraceElement.getMethodName();
    final int stackTraceLineNumber = stackTraceElement.getLineNumber();
    Class<?> stackTraceClass = Class.forName(stackTraceClassName);

    // I am only using AtomicReference as a container to dump a String into, feel free to ignore it for now
    final AtomicReference<String> methodDescriptorReference = new AtomicReference<String>();

    String classFileResourceName = "/" + stackTraceClassName.replaceAll("\\.", "/") + ".class";
    InputStream classFileStream = stackTraceClass.getResourceAsStream(classFileResourceName);

    if (classFileStream == null) {
        throw new RuntimeException("Could not acquire the class file containing for the calling class");
    }

    try {
        ClassReader classReader = new ClassReader(classFileStream);
        classReader.accept(
                new EmptyVisitor() {
                    @Override
                    public MethodVisitor visitMethod(int access, final String name, final String desc, String signature, String[] exceptions) {
                        if (!name.equals(stackTraceMethodName)) {
                            return null;
                        }

                        return new EmptyVisitor() {
                            @Override
                            public void visitLineNumber(int line, Label start) {
                                if (line == stackTraceLineNumber) {
                                    methodDescriptorReference.set(desc);
                                }
                            }
                        };
                    }
                },
                0
            );
    } finally {
        classFileStream.close();
    }

    String methodDescriptor = methodDescriptorReference.get();

    if (methodDescriptor == null) {
        throw new RuntimeException("Could not find line " + stackTraceLineNumber);
    }

    for (Method method : stackTraceClass.getMethods()) {
        if (stackTraceMethodName.equals(method.getName()) && methodDescriptor.equals(Type.getMethodDescriptor(method))) {
            return method;
        }
    }

    throw new RuntimeException("Could not find the calling method");
}

Problem

I would like to get the calling method `java.lang.reflect.Method`. NOT the name of the method. Here is an example how to get the callers Class. ``` // find the callers class Thread t = Thread.getCurrentThread(); Class<?> klass = Class.forName(t.getStackTrace()[2].getClassName()); // do something with the class (like processing its annotations) ... ``` It's for testing purpose only!

Original source