使用@Cacheable方法创建实现ApplicationListener的bean时出错

Question

我们在部署应用程序时遇到了问题，经过一段时间的研究，我们找到了问题的根源，但我们不知道为什么会发生这种情况。

在Spring上下文初始化时，应用程序尝试将bean“bar”连接到bean“foo”上Bar’bean实现了接口ApplicationListener，并且还有一个@Cacheable方法。由于某种原因，我们不知道，bean创建出现了崩溃。删除@Cacheable或使bean不是ApplicationListener的实例，应用程序运行正常。

可能是对ApplicationListener和/或@Cacheable的误解，但发生此错误的原因是什么？为什么“酒吧豆”是非法的？Spring版本是3.2.9。

Spring上下文文件

<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:cache="http://www.springframework.org/schema/cache"
   xmlns:task="http://www.springframework.org/schema/task"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans.xsd
   http://www.springframework.org/schema/cache
   http://www.springframework.org/schema/cache/spring-cache.xsd
   http://www.springframework.org/schema/task
   http://www.springframework.org/schema/task/spring-task.xsd">

<bean id="applicationContextProvder" class="com.mycompany.ApplicationContextProvider"/>

<!-- CACHE -->
<cache:annotation-driven cache-manager="springEhCacheManager"/>

<bean id="ehCacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">
    <property name="configLocation" value="/WEB-INF/conf/ehcache.xml"/>
</bean>

<bean id="springEhCacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager">
    <constructor-arg ref="ehCacheManager"/>
</bean>

<bean id="cacheProvider" class="org.springmodules.cache.provider.ehcache.EhCacheFacade">
    <property name="cacheManager" ref="ehCacheManager"/>
</bean>

<bean id="cacheService" class="com.myapp.cache.DefaultEHCacheServiceImp">
    <constructor-arg index="0" ref="ehCacheManager"/>
</bean>

<!-- ALIVE -->
<bean id="voldemortAlive"
      class="com.myapp.voldemort.VoldemortAliveImp">
</bean>

<bean id="atlasAlive"
      class="com.myapp.atlas.AtlasAliveImp">
</bean>



<task:annotation-driven executor="myExecutor" scheduler="myScheduler"/>
<task:executor id="myExecutor" pool-size="5"/>
<task:scheduler id="myScheduler" pool-size="10"/>

<!-- custom beans defined -->

<bean id="updatersSynchronizedTaskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor"/>
<bean id="updatersSynchronizedTaskExporter" class="org.springframework.jmx.export.MBeanExporter" lazy-init="false"/>

福课

package com.foo

@Service
public class Foo {

    @Autowired
    private Bar bar;

    ... lots of stuff here ...

    @PostConstruct
    protected void init() {
         ... method body ...
    }

... more logic ...

}

酒吧班

package com.bar

@Repository
public class Bar extends BarParent implements ApplicationListener<BarEvent>   {

... more stuff ...

    @Cacheable("cache_name")
    public List<Baz> cachedMethod(final Integer code) {
        ... some logic here ...
    }
...
}

给予的例外

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.bar.Bar com.foo.Foo.bar; nested exception is java.lang.IllegalArgumentException: Can not set com.bar.Bar field com.foo.Foo.bar to $Proxy86
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:517)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:286)
... 63 more
Caused by: java.lang.IllegalArgumentException: Can not set com.bar.Bar field com.foo.Foo.bar to $Proxy86
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:146)
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:150)
at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:63)
at java.lang.reflect.Field.set(Field.java:657)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:513)
... 65 more

提前谢谢你。

Answer 1

改变

<cache:annotation-driven cache-manager="springEhCacheManager"/>

到

<cache:annotation-driven cache-manager="springEhCacheManager" proxy-target-class="true"/>

由于其中一种方法是@Cacheable，Spring会为条生成一个代理。由于默认代理生成策略基于Java动态代理，并且Bar实现接口ApplicationListener，因此生成的代理是ApplicationListener的子类型，而不是Bar。因此，当遇到@Autowired Bar时，Spring会尝试注入一个不是Bar子类型的代理实例，因此会出现错误。

通过将proxy target class设置为true，Spring将被迫使用CGLIB生成基于类的代理，@Autowired Bar将注入一个Bar实例。