来张图

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前置

最近在开发一个web项目，集成hibernate，且使用了OpenSessionInViewFilter，发现spring的事务无效了。进行了如下配置：

spring上下文的applicationContext.xml

<context:component-scan base-package="com.github.mypost">   
    <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>   
    <context:exclude-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice"/>
</context:component-scan>

<!-- 事务管理器 -->
<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory"></property>
</bean>

<!-- 事务特性  -->
<tx:advice id="txAdvice" transaction-manager="transactionManager" >
    <tx:attributes>
        <tx:method name="save*" propagation="REQUIRED"/>
        <tx:method name="add*" propagation="REQUIRED"/>
        <tx:method name="insert*" propagation="REQUIRED"/>
        <tx:method name="create*" propagation="REQUIRED"/>
        <tx:method name="delete*" propagation="REQUIRED"/>
        <tx:method name="remove*" propagation="REQUIRED"/>
        <tx:method name="update*" propagation="REQUIRED"/>
        <tx:method name="modify*" propagation="REQUIRED"/>
        <tx:method name="edit*" propagation="REQUIRED"/>
        <tx:method name="*" read-only="true" />
    </tx:attributes>
</tx:advice>

<aop:config proxy-target-class="true">
    <aop:pointcut id="serviceMethod" expression="execution(* com.github.mypost.*.service..*+.*(..))"/>
    <aop:advisor advice-ref="txAdvice" pointcut-ref="serviceMethod" />
</aop:config>

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

<!-- annotation trasaction -->
<tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>

springmvc的上下文配置webApplicationContext.xml

<context:component-scan base-package="com.github.mypost">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice"/>
</context:component-scan>

<!--默认的注解映射的支持 -->
<mvc:annotation-driven conversion-service="conversionService"/>

<!-- 拦截器 -->
<mvc:interceptors>
    <bean class="com.github.mypost.commons.web.interceptor.BaseInterceptor"></bean>
</mvc:interceptors>

<!--视图解释器,根据不同的请求展示不同的View -->
<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
    <property name="viewResolvers">
        <list>
            <!--视图解释类 -->
            <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
                <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
                <property name="prefix" value="/WEB-INF/view/" />
                <property name="suffix" value=".jsp" />
            </bean>
        </list>
    </property>
</bean>

<bean id="jsonHttpMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" />

<!-- 配置文件上传解析器 -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="defaultEncoding" value="UTF-8" />
</bean>

<mvc:view-controller path="/" view-name="index"/>

一直以为是使用了OpenSessionInViewFilter这个类库的原因导致的失败，最后才发现是由于context:component-scan的use-default-filters导致的问题。

分析

1. <context:component-scan>会交给org.springframework.context.config.ContextNamespaceHandler处理；

registerBeanDefinitionParser("component-scan", new ComponentScanBeanDefinitionParser());

2. <context:component-scan>的use-default-filters默认true，会交给ClassPathScanningCandidateComponentProvider进行扫描，看代码：

protected void registerDefaultFilters() {
    this.includeFilters.add(new AnnotationTypeFilter(Component.class));
    ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();
    try {
        this.includeFilters.add(new AnnotationTypeFilter(
                ((Class<? extends Annotation>) cl.loadClass("javax.annotation.ManagedBean")), false));
        logger.debug("JSR-250 'javax.annotation.ManagedBean' found and supported for component scanning");
    }
    catch (ClassNotFoundException ex) {
        // JSR-250 1.1 API (as included in Java EE 6) not available - simply skip.
    }
    try {
        this.includeFilters.add(new AnnotationTypeFilter(
                ((Class<? extends Annotation>) cl.loadClass("javax.inject.Named")), false));
        logger.debug("JSR-330 'javax.inject.Named' annotation found and supported for component scanning");
    }
    catch (ClassNotFoundException ex) {
        // JSR-330 API not available - simply skip.
    }
}

可以看到默认ClassPathBeanDefinitionScanner会自动注册对@Component、@ManagedBean、@Named注解的Bean进行扫描。如果细心，到此就找到问题根源了。

3. 对exclude-filter，include-filter进行过滤
   首先通过exclude-filter 进行黑名单过滤；
   然后通过include-filter 进行白名单过滤；
   否则默认排除。

结论

<context:component-scan base-package="com.github.mypost" use-default-filters="false"> 
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/> 
     <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice"/>
</context:component-scan>

那么这段代码不仅仅对@Controller的注解Bean进行了扫描，而且对@Compoent注解也扫描了，子注解@Service，@Repository也进行了扫描，所以原来mvc的上下文的Bean被后面的bean替换了。所以如下解决方法：

1. 如果不需要默认的，则use-default-filters=“false”禁用掉。
2. 直接写明具体Controller包名称。