spring ioc injecting concrete implementation of interface to test

问题

I have the following setup:

@Component
public class ImplOne implements IFace{
}

@Component
public class ImplTwo implements IFace{
}

public interface IFace{
}

I am trying to get a reference of ImplOne by type:

@RunWith(SpringJUnit4ClassRunner.class)
public class ImplOneTest {
  @Autowired
  private ImplOne impl;

  @Test
  public void test(){
    Assert.assertNotNull(impl);
  }
}

Though with this I get the following exception:

org.springframework.beans.factory.NoSuchBeanDefinitionException:
No matching bean of type [some.package.TestBean] 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)}

I tried the following workarounds:

Remove "implements IFace" from ImplOne so the implementation class itself gets Proxied by cglib. Not acceptable because I also need to be able to get all implementations of IFace in my application code.
Doing method injection via a @Autowired public void setImplOne(IFace[] beans) and filtering the instance through instanceof check does not work, because the injected beans are subclasses of type java.lang.reflect.Proxy which doesn't offer any useful methods.
Changing @Component of ImplOne to @Component("implone") and using @Qualifier("implone").

Code:

@RunWith(SpringJUnit4ClassRunner.class)
public class ImplOneTest {
  @Autowired
  @Qualifier("implone")
  private ImplOne impl;

  @Test
  public void test(){
    Assert.assertNotNull(impl);
  }
}

But I don't like the idea of having to name my beans just to be able to inject the concrete implementation.

Is there some way to do this elegantly, or atleast in some manner that only affects my test code? Also is there some special reason why my first example is unsupported?

回答1:

Check if the exception is about the beans you think it is. Because the names don't match
Even if 1 is fixed, it is preferable to autowire by interface, not by concrete implementation. Most often (I can' know if this is true in your case), concrete implementations are proxied by spring (for transaction support, for example), and can be injected by interface only. And since you have two implementations of one interface, you have to provide a name, and either use @Autowired + @Qualifier, or use @Resource(name="") to inject what you want. And there is nothing wrong with this.

回答2:

Ok, today i found a way to make this work afterall. Seems like the Spring-AOP-Autoproxy was to blame for this not to work.

Currently I am using AJDT in Eclipse for compile time weaving (CTW) and the TransactionAnnotationAspect. I also removed the aspectjweaver and cglib dependency in my project, so autoproxy is not even supported anymore, after removing the following config part from applicationcontext:

<aop:pointcut id="serviceOperation" expression="execution(* some.package..*(..)) &amp;&amp; @target(org.springframework.stereotype.Service)" />
    <aop:advisor pointcut-ref="serviceOperation" advice-ref="serviceTxAdvice" />
</aop:config>
<tx:advice id="serviceTxAdvice" transaction-manager="transactionManager">
    <tx:attributes>
        <tx:method name="*" read-only="true" propagation="SUPPORTS" />
    </tx:attributes>
</tx:advice>

And that was also the reason why @Configurable didn't work for me...

回答3:

Adding the following line worked for me:

<aop:aspectj-autoproxy proxy-target-class="true"/>

来源：https://stackoverflow.com/questions/1882959/spring-ioc-injecting-concrete-implementation-of-interface-to-test

标签

Spring

dependency-injection

inversion-of-control

javabeans