Autowiring of beans generated by EasyMock factory-

问题:

I have a problem that seems really strange to me. I have the following setup:

An interface:

package com.example;

public interface SomeDependency {
}

A spring component:

package com.example;

@Component
public class SomeClass {
}

A spring test config with a mocked bean generated by EasyMock:

<beans ....>
    <context:component-scan base-package="com.example"/>

    <bean id="someInterfaceMock" class="org.easymock.EasyMock" factory-method="createMock">
        <constructor-arg value="com.example.SomeDependency" />
    </bean> 
</beans>

And a unit test:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("/testconfig.xml")
public class SomeClassTest {

    @Autowired
    SomeClass someClass;

    @Autowired
    SomeDependency someDependency;

    @Test
    public void testSomeClass() throws Exception {
        assertNotNull(someClass);
    }

    @Test
    public void testSomeDependency() throws Exception {
        assertNotNull(someDependency);
    }
}

The project compiles and the tests pass without any problem, i.e. autowiring of both SomeClass (a "real" object) and SomeDependency (a mock object generated by EasyMock) succeed.

However, if I change the implementation of SomeClass to:

@Component
public class SomeClass {

    @Autowired
    SomeDependency someDependency;
}

both tests fail because

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [com.example.SomeDependency] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

So my questions are:

1. Why does Spring fail to autowire the dependency to SomeClass (when it succeeds autowiring the same dependency to SomeClassTest)?
2. How can I change the SomeClassTest or testconfig.xml to make the tests pass?

Comment: In reality the class represented by SomeClass is part of a framework. Consequently, it cannot easily be updated, at least not within reasonable time.

Dependencies:

• Spring: 3.0.5.RELEASE
• EasyMock: 3.0

Edit:

As of Spring 3.2 RC1, the problem with generic factory methods and mock objects has been solved.

/Mattias

回答1:

It seems the order of the definitions in the xml actually matter when using factories to create beans with autowiring. If you place the declaration of someInterfaceMock above component-scan it will work.

Some clarification why: When Spring tries to autowire SomeClass it searches for a bean of type SomeDependency. At this stage someInterfaceMock is still a factory so Spring checks the signature of the factory method EasyMock.createMock(...) which returns <T> so Spring only finds an Object which isn't the type required.

A better way would be to use Spring's FactoryBean interface to create your mocks.

Here is a basic implementation that should work:

public class EasyMockFactoryBean<T> implements FactoryBean<T> {
    private Class<T> mockedClass;

    public void setMockedClass(Class mockedClass) {
        this.mockedClass = mockedClass;
    } 

    public T getObject() throws Exception {
        return EasyMock.createMock(mockedClass);
    }

    public Class<T> getObjectType() {
        return mockedClass;
    }

    public boolean isSingleton() {
        return true;
    } 

}

Here is the bean definition (the order won't matter!):

<bean class="com.example.EasyMockFactoryBean">
    <property name="mockedClass" value="com.example.Dependancy"/>
</bean>