Spring中Aspectj和Schema-based AOP混用引起的错误

         前几天要在项目中增加一个新功能用来监控某些模块的运行情况，自然就想到了使用Spring的AOP来实现。之前已经有类似的AOP代码，使用的是Schema-based形式配置的，也就是在Spring的ApplicationContext.xml中加入了：

其中sampleService和sampleAdvice都是通过：

自动引入的。

提交代码到测试服务器上进行测试，结果启动时就遇到了第一个问题：

 ERROR [org.springframework.web.servlet.DispatcherServlet] [Thread-2] Context initialization failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'service1' defined in file [/opt/myapp/bin/WEB-INF/classes/com/nokia/myapp/Service1.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.nokia.myapp.Service1]: Constructor threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'service2': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.nokia.myapp.Service1 com.nokia.myapp.Service2.locationService; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'service1': Requested bean is currently in creation: Is there an unresolvable circular reference?

        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:965) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]

        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:911) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]

        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]

        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) ~[spring-beans-3.0.5.RELEASE.jar:3.0.5.RELEASE]

……

        根据提示查看代码，发现在Service2中通过@Autowired引入了Service1，而在Service1中也通过@Autowired引入了Service2。于是去掉了Service2在Service1中引用，而后在需要用的时候通过ApplicationContext.getBean(String beanName)获取Service2。

        修正了上面的错误，再次测试，程序可以正常启动，但是有些程序运行出现了奇怪的问题：每次ApplicationConext.getBeansOfType(Class class)获取sampleService时，总是会获取到其他的Bean，导致程序运行异常（不过本地Eclipse中运行测试没有问题）。使用Eclipse的Remote Debug功能连到开发服务器上调试，发现其他类getClass()获取的都是class com.nokia.myapp.Service2$$EnhancerByCGLIB$$ccadc5e，而SampleService却是$Proxy119。百思不得其解。

        最后请教了对Spring框架很熟悉的同事，终于发现了问题的原因：

Spring AOP uses either JDK dynamic proxies or CGLIB to create the proxy for a given target object. (JDK dynamic proxies are preferred whenever you have a choice).

If the target object to be proxied implements at least one interface then a JDK dynamic proxy will be used. All of the interfaces implemented by the target type will be proxied. If the target object does not implement any interfaces then a CGLIB proxy will be created.

Spring又在实现了接口的SampleService的代理类外面包了JDK的代理实现，所以就造成了这个问题。