private void generateInterceptorHandledMethod()

in services/interceptor/impl/src/main/java/org/apache/karaf/service/interceptor/impl/runtime/proxy/AsmProxyFactory.java [187:336]
108 lines of code
17 McCabe index (conditional complexity)

    private void generateInterceptorHandledMethod(final ClassWriter cw, final Method method, final int methodIndex,
                                                  final Class<?> classToProxy, final String proxyClassFileName) {
        if ("<init>".equals(method.getName())) {
            return;
        }

        final Class<?> returnType = method.getReturnType();
        final Class<?>[] parameterTypes = method.getParameterTypes();
        final Class<?>[] exceptionTypes = method.getExceptionTypes();
        final int modifiers = method.getModifiers();
        if (Modifier.isFinal(modifiers) || Modifier.isStatic(modifiers)) {
            throw new IllegalStateException("It's not possible to proxy a final or static method: " + classToProxy.getName() + " " + method.getName());
        }

        // push the method definition
        final int modifier = modifiers & (ACC_PUBLIC | ACC_PROTECTED | ACC_VARARGS);

        final MethodVisitor mv = cw.visitMethod(modifier, method.getName(), Type.getMethodDescriptor(method), null, null);
        mv.visitCode();
        // push try/catch block, to catch declared exceptions, and to catch java.lang.Throwable
        final Label l0 = new Label();
        final Label l1 = new Label();
        final Label l2 = new Label();

        if (exceptionTypes.length > 0) {
            mv.visitTryCatchBlock(l0, l1, l2, "java/lang/reflect/InvocationTargetException");
        }

        // push try code
        mv.visitLabel(l0);
        final String classNameToOverride = method.getDeclaringClass().getName().replace('.', '/');
        mv.visitLdcInsn(Type.getType("L" + classNameToOverride + ";"));

        // the following code generates the bytecode for this line of Java:
        // Method method = <proxy>.class.getMethod("add", new Class[] { <array of function argument classes> });

        // get the method name to invoke, and push to stack
        mv.visitLdcInsn(method.getName());

        // create the Class[]
        createArrayDefinition(mv, parameterTypes.length, Class.class);

        int length = 1;

        // push parameters into array
        for (int i = 0; i < parameterTypes.length; i++) {
            // keep copy of array on stack
            mv.visitInsn(DUP);

            final Class<?> parameterType = parameterTypes[i];

            // push number onto stack
            pushIntOntoStack(mv, i);

            if (parameterType.isPrimitive()) {
                String wrapperType = getWrapperType(parameterType);
                mv.visitFieldInsn(GETSTATIC, wrapperType, "TYPE", "Ljava/lang/Class;");
            } else {
                mv.visitLdcInsn(Type.getType(parameterType));
            }

            mv.visitInsn(AASTORE);

            if (Long.TYPE.equals(parameterType) || Double.TYPE.equals(parameterType)) {
                length += 2;
            } else {
                length++;
            }
        }

        // the following code generates bytecode equivalent to:
        // return ((<returntype>) invocationHandler.invoke(this, {methodIndex}, new Object[] { <function arguments }))[.<primitive>Value()];

        final Label l4 = new Label();
        mv.visitLabel(l4);
        mv.visitVarInsn(ALOAD, 0);
        mv.visitFieldInsn(GETFIELD, proxyClassFileName, FIELD_INTERCEPTOR_HANDLER, Type.getDescriptor(InterceptorHandler.class));
        mv.visitFieldInsn(GETSTATIC, proxyClassFileName, FIELD_INTERCEPTED_METHODS, Type.getDescriptor(Method[].class));
        if (methodIndex < 128) {
            mv.visitIntInsn(BIPUSH, methodIndex);
        } else if (methodIndex < 32267) {
            mv.visitIntInsn(SIPUSH, methodIndex);
        } else {
            throw new IllegalStateException("Sorry, we only support Classes with 2^15 methods...");
        }

        mv.visitInsn(AALOAD);
        pushMethodParameterArray(mv, parameterTypes);
        mv.visitMethodInsn(INVOKEINTERFACE, Type.getInternalName(InterceptorHandler.class), "invoke",
                "(Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;", true);
        mv.visitTypeInsn(CHECKCAST, getCastType(returnType));
        if (returnType.isPrimitive() && (!Void.TYPE.equals(returnType))) {
            // get the primitive value
            mv.visitMethodInsn(INVOKEVIRTUAL, getWrapperType(returnType), getPrimitiveMethod(returnType),
                    "()" + Type.getDescriptor(returnType), false);
        }

        mv.visitLabel(l1);
        if (!Void.TYPE.equals(returnType)) {
            mv.visitInsn(getReturnInsn(returnType));
        } else {
            mv.visitInsn(POP);
            mv.visitInsn(RETURN);
        }

        // catch InvocationTargetException
        if (exceptionTypes.length > 0) {
            mv.visitLabel(l2);
            mv.visitVarInsn(ASTORE, length);

            Label l5 = new Label();
            mv.visitLabel(l5);

            for (int i = 0; i < exceptionTypes.length; i++) {
                Class<?> exceptionType = exceptionTypes[i];

                mv.visitLdcInsn(Type.getType("L" + exceptionType.getCanonicalName().replace('.', '/') + ";"));
                mv.visitVarInsn(ALOAD, length);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/reflect/InvocationTargetException", "getCause",
                        "()Ljava/lang/Throwable;", false);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Object", "getClass", "()Ljava/lang/Class;", false);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Object", "equals", "(Ljava/lang/Object;)Z", false);

                Label l6 = new Label();
                mv.visitJumpInsn(IFEQ, l6);

                Label l7 = new Label();
                mv.visitLabel(l7);

                mv.visitVarInsn(ALOAD, length);
                mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/reflect/InvocationTargetException", "getCause",
                        "()Ljava/lang/Throwable;", false);
                mv.visitTypeInsn(CHECKCAST, getCastType(exceptionType));
                mv.visitInsn(ATHROW);
                mv.visitLabel(l6);

                if (i == (exceptionTypes.length - 1)) {
                    mv.visitTypeInsn(NEW, "java/lang/reflect/UndeclaredThrowableException");
                    mv.visitInsn(DUP);
                    mv.visitVarInsn(ALOAD, length);
                    mv.visitMethodInsn(INVOKESPECIAL, "java/lang/reflect/UndeclaredThrowableException", "<init>",
                            "(Ljava/lang/Throwable;)V", false);
                    mv.visitInsn(ATHROW);
                }
            }
        }

        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }