Question

I’m writing an integration test where an application context xml is initialized during startup. There are several test methods in the test class which make use of a specific bean ‘X'(already defined in the xml). My actual requirement is to mock bean X only for one of the test methods.

Inside a test method: I tried creating a separate application context using ClassPathXMLApplicationContext with only the mock bean ‘M’.

Now I have two Application Contexts (AC):
1. One created during test case startup (which contains the actual bean X) and
2. One created using ClassPathXMLApplicationContext within the test method (which has the mock bean M).

I want to replaced the actual bean definition ‘X’ within AC:1, using the mock bean definition ‘M’ from AC:2.

Can somebody throw some light on this please?

Answer 1

There is not a clear way to replace a a bean in a refreshed ApplicationContext unless you close it and refresh it again.

To emulate it, the common approach is to use a Proxy of the bean that you want to replace and change the target at runtime.

You can do it easily using the framework aop support classes:

<bean id="realBean" class="RealClass" />
<bean id="mockBean" class="MockClass" />
<bean id="targetSource" class="org.springframework.aop.target.HotSwappableTargetSource">
    <constructor-arg ref="realBean" />
</bean>

<bean id="bean" class="org.springframework.aop.framework.ProxyFactoryBean">
    <property name="targetSource" ref="targetSource" />
</bean>

 

@Test
public void testWithMockBean() {
Object real = targetSource.swap(mock);
....
// do your test work
...
targetSource.swap(real);

}