aop aspects as mock in spring test - spring-mvc

Question

I came across an interesting article: AOP Aspects as mocks in JUnit
Since I have requirement to mock multiple final and private static variables, I am planning to use AOP in place of reflection or PowerMockito as they are causing issues with SpringJUnit4ClassRunner.
Is there any way I can use #Aspect for test classes without using the annotation #EnableAspectJAutoProxy? (I want to use an aspect targeting class X only in one test case.)
This is a sample of what I want to do.
The question is answered(adding for discussion on what could be done)
//External class
public final class ABC(){
public void method1() throws Exception {}
}
#Service
public void DestClass() {
private static final ABC abc = new ABC();
public Object m() {
// code (...)
try {
abc.method1();
}
catch(Exception e) {
// do something (...)
return null;
}
// more code (...)
}
}

Answer 1

Spring framework allows to programmatically create proxies that advise target objects , without configuring through #EnableAspectJAutoProxy or <aop:aspectj-autoproxy>
Details can be found in the documentation section : Programmatic Creation of #AspectJ Proxies and the implementation is pretty simple.
Example code from the documentation.
// create a factory that can generate a proxy for the given target object
AspectJProxyFactory factory = new AspectJProxyFactory(targetObject);
// add an aspect, the class must be an #AspectJ aspect
// you can call this as many times as you need with different aspects
factory.addAspect(SecurityManager.class);
// you can also add existing aspect instances, the type of the object supplied must be an #AspectJ aspect
factory.addAspect(usageTracker);
// now get the proxy object...
MyInterfaceType proxy = factory.getProxy();
Please note that with Spring AOP , only method executions can be adviced. Excerpt from the documentation
Spring AOP currently supports only method execution join points
(advising the execution of methods on Spring beans). Field
interception is not implemented, although support for field
interception could be added without breaking the core Spring AOP APIs.
If you need to advise field access and update join points, consider a
language such as AspectJ.
The document shared with the question is about aspectj and without providing the sample code to be adviced it is hard to conclude if the requriement can acheived through Spring AOP. The document mentions this as well.
One example of the integration of AspectJ is the Spring framework,
which now can use the AspectJ pointcut language in its own AOP
implementation. Spring’s implementation is not specifically targeted
as a test solution.
Hope this helps.
--- Update : A test case without using AOP ---
Consider the external Class
public class ABCImpl implements ABC{
#Override
public void method1(String example) {
System.out.println("ABC method 1 called :"+example);
}
}
And the DestClass
#Service
public class DestClass {
private static final ABC service = new ABCImpl();
protected ABC abc() throws Exception{
System.out.println("DestClass.abc() called");
return service;
}
public Object m() {
Object obj = new Object();
try {
abc().method1("test");
} catch (Exception e) {
System.out.println("Exception : "+ e.getMessage());
return null;
}
return obj;
}
}
Following test class autowires the DestClass bean with overridden logic to throw exception . This code can be modified to adapt to your requirement.
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = { DestClassSpringTest.TestConfiguration.class })
public class DestClassSpringTest {
#Configuration
static class TestConfiguration {
#Bean
public DestClass destClass() {
return new DestClass() {
protected ABC abc() throws Exception {
// super.abc(); // not required . added to demo the parent method call
throw new Exception("Custom exception thrown");
}
};
}
}
#Autowired
DestClass cut;
#Test
public void test() {
Object obj = cut.m();
assertNull(obj);
}
}
Following will be the output log
DestClass.abc() called // this will not happen if the parent method call is commented in DestClassSpringTest.TestConfiguration
Exception : Custom exception thrown

Answer 2

The article you are referring to is using full AspectJ, not Spring AOP. Thus, you do not need any #EnableAspectJAutoProxy for that, just
either the AspectJ load-time weaver on the command line when running your test via -javaagent:/path/to/aspectjweaver.jar
or the AspectJ compiler activated when compiling your tests (easily done via AspectJ Maven plugin if you use Maven)
Both approaches are completely independent of Spring, will work in any project and even when using Spring also work when targeting execution of third party code because no dynamic proxies are needed unlike in Spring AOP. So there is no need to make the target code into a Spring bean or to create a wrapper method in your application class for it. When using compile-time weaving you can even avoid weaving into the third party library by using call() instead of execution() pointcut. Spring AOP only knows execution(), AspectJ is more powerful.
By the way: Unfortunately both your question and your comment about the solution you found are somewhat fuzzy and I do not fully understand your requirement. E.g. you talked about mocking final and private static variables, which would also be possible in other ways with AspectJ by using set() and/or get() pointcuts. But actually it seems you do not need to mock the field contents, just stub the results of method calls upon the objects assigned to those fields.