spring循环依赖问题分析

新搞了一个单点登录的项目，用的cas，要把源码的cas-webapp改造成适合我们业务场景的项目，于是新加了一些spring的配置文件。

但是在项目启动时报错了，错误日志如下：

一月 08, 2016 11:01:34 下午 org.apache.catalina.core.StandardContext filterStart
严重: Exception starting filter springSecurityFilterChain
org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'functionServiceImpl': Bean with name 'functionServiceImpl' has been injected into other beans [platformServiceImpl] in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:548)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:389)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:294)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
    at org.jasig.cas.web.init.SafeContextLoaderListener.contextInitialized(SafeContextLoaderListener.java:75)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5003)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5517)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1574)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1564)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

去stackoverflow上面搜，说是spring循环依赖导致的。但是问了组里一个技术牛，说如果是出现spring循环依赖，在启动项目的时候是不会报错的，spring的循环依赖在运行的时候才会报错。

循环依赖也可能出现在maven里，如果maven配置中出现了循环依赖，编译的时候就会报错。

那么，究竟是什么原因，我现在还不知道。

在我的web.xml文件中，引入了两次spring的applicationContext.xml文件。

  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
      /WEB-INF/spring-configuration/*.xml
      /WEB-INF/deployerConfigContext.xml
      classpath:spring/applicationContext.xml
    </param-value>
  </context-param>

当我去掉我自己的spring配置时，项目启动就不报错了。

  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
      /WEB-INF/spring-configuration/*.xml
      /WEB-INF/deployerConfigContext.xml      
    </param-value>
  </context-param>

那是不是因为加载了两个applicationContext.xml，就相当于初始化了两个spring容器，有的单例类只允许存在一个实例，但是却出现了两个容器的bean，所以报错了呢？

具体问题待排查。

问题原因查到了：

由于刚开始配置spring的时候加载了2遍applicationContext.xml,其中有一个动态代理切面的配置在两个配置文件中都存在重复了。详情见：

http://www.cnphp6.com/archives/22031

其实，还是因为bean加载重复了。