Spring Test: Inject Mock Object into proxy-based Spring bean.(Like bean with @Transactional or @Aync ...)

Spring Test, which I have to say, is the perfect lib for testing projects build on Spring.

There is one very useful class called "ReflectionTestUtils". With that, we dont need to put any setter or getter  for autowired fields inside our services and we can partially replace one autowired field/service to our defined mock object. Very convenient and flexible.

Example:

FooDao mockFooDao = Mockito.mock(FooDao.class);
Mockito.when(mockFooDao.foo()).thenReturn("Var");
ReflectionTestUtils.setField(fooService, "fooDao", mockFooDao);

There is one thing we need to pay attention, is, component bean may be wrapped by proxy class when we use annotations from spring like @Transactional or @Aync. In this case, we need to unwrap the bean before we inject the mock object, otherwise, the "ReflectionTestUtils" cannot inject the mock object, because the "fooService" is proxy object, does not have the "fooDao" field inside it!

So we need to unwrap the bean like this:

protected Object unwrapService(Object service) throws Exception {
   if(AopUtils.isAopProxy(service) && service instanceof Advised) {
 Object target = ((Advised) service).getTargetSource().getTarget();
 return target;
   }
   return null;
}

And:

ReflectionTestUtils.setField(unwrapService(fooService), "fooDao", mockFooDao);

In this way, it works perfect.

Enjoy.