EasyMock Objects Injection using Spring and Annotations

Declaring EasyMock objects as spring beans is easy...

However, if the bean you want to test is dynamically proxied, you will get a ClassCastException. To work around this, you can create a custom annotation and bean post processor. This will allow you to annotate fields with @MockObject and Spring will provide the mock object using dependency injection...

Custom Annotation

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
@Documented
public @interface MockObject {}

Custom Spring Bean Post Processor

@Component
public class MockObjectBeanPostProcessor implements BeanPostProcessor
{
private Log logger = LogFactory.getLog(this.getClass());

/* (non-Javadoc)
* @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessBeforeInitialization
*/
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException
{
// get all the fields
Field[] fields = bean.getClass().getDeclaredFields();
for(Field field : fields)
{
// check if field is annotated by Environment Property
if(field.isAnnotationPresent(MockObject.class))
{
try
{
field.setAccessible(true);
field.set(bean, EasyMock.createMock(field.getType()));
} catch (Exception e) {
logger.warn(e);
}
}
}
return bean;
}

/* (non-Javadoc)
* @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessAfterInitialization
*/
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException
{
// do nothing, return original bean
return bean;
}
}

Sample JUnit Test

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"/spring-test.xml"})
public class MailProcessorTest
{
@MockObject private MailProcessor mailProcessor;

@Test
public void test()
{
// setup test behavior

EasyMock.replay(mailProcessor);
}
}

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