ContextLoaderListener 与 ServletDispatcher

2022-03-21 16:58:46

网上找了一下关于ContextLoaderListener和ServletDispatcher的解释,这是原文

http://simone-folino.blogspot.com/2012/05/dispatcherservlet-vs.html

http://syntx.co/languages-frameworks/difference-between-loading-context-via-dispatcherservlet-and-contextloaderlistener/

总结如下:

Spring中有两种上下文环境-"Application Context和Web Application Context",他们分别对应ContextLoaderListener和ServletDispatcher,且都可以用来配置bean的注入,装配,和AOP

1. ContextLoaderListener

ContextLoaderListener通过读取contextConfigLocation参数来读取配置参数,一般来说它配置的是Spring项目的中间层,服务层组件的注入,装配,AOP.

对应到Spring的自动装配机制<context:component-scan>就是以下几种注解的装配

DAO: such as @Repository bean
Entity: such as @Entity bean
Service: such as @Service bean

(以上内容来自引用博文)

下面是一个典型web.xml中加载ContextLoaderListener的代码片段

    <!-- 定义参数 -->

    <context-param>

        <param-name>contextConfigLocation</param-name>

        <param-value>classpath*:spring/config/applicationContext.xml</param-value>

    </context-param>

    <!-- 定义Listener -->

    <listener>

        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>

    </listener>

以及 applicationContext.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<beans xmlns="http://www.springframework.org/schema/beans"

 xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"

 xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx"

 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jaxrs="http://cxf.apache.org/jaxrs"

 xmlns:cxf="http://cxf.apache.org/core"

 xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd http://cxf.apache.org/core http://cxf.apache.org/schemas/core.xsd   http://www.springframework.org/schema/beans  http://www.springframework.org/schema/beans/spring-beans-3.0.xsd    http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context-3.0.xsd    http://www.springframework.org/schema/jee  http://www.springframework.org/schema/jee/spring-jee-3.0.xsd    http://www.springframework.org/schema/tx   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

     <context:annotation-config />

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

     <context:component-scan base-package="com.simonefolinoblogspot.dao" >

        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>

     </context:component-scan>

     ...

</beans>

可以看到ContextLoaderListener的配置文件都是中间层,数据层,DAO之类的

2. ServletDispatcher

ServletDispatcher通过读取<servlet-name>-servlet.xml文件来读取配置,如果文件不存在,则可以通过servlet标签内的

        <init-param>

            <param-name>contextConfigLocation</param-name>

            <param-value>classpath*:spring/config/dispatcher-servlet.xml</param-value>

        </init-param>

来指定配置文件,它配置的是Web层组件的注入,装配和AOP

Controllers
ViewResolvers
LocaleResolvers
ThemeResolvers

下面是一个典型配置web.xml

<servlet>

 <servlet-name>addressbook</servlet-name>

 <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

 <init-param>

  <param-name>contextConfigLocation</param-name>

  <param-value>/WEB-INF/spring/spring-mvc.xml</param-value>

 </init-param>

 <load-on-startup>1</load-on-startup>

</servlet>

spring-mvc.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

 xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context"

 xmlns:tx="http://www.springframework.org/schema/tx"

 xsi:schemaLocation="http://www.springframework.org/schema/beans

                           http://www.springframework.org/schema/beans/spring-beans.xsd

                           http://www.springframework.org/schema/context

                           http://www.springframework.org/schema/context/spring-context.xsd

                           http://www.springframework.org/schema/tx

                           http://www.springframework.org/schema/tx/spring-tx.xsd

                           http://www.springframework.org/schema/aop

                           http://www.springframework.org/schema/aop/spring-aop.xsd

                           ">

   <context:annotation-config />

   <context:component-scan base-package="com.simonefolinoblogspot.controller" >

        <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>

   </context:component-scan>

   <bean id="viewResolver"

  class="org.springframework.web.servlet.view.InternalResourceViewResolver">

  <property name="viewClass"

   value="org.springframework.web.servlet.view.JstlView" />

  <property name="prefix" value="/WEB-INF/pages/" />

  <property name="suffix" value=".jsp" />

   </bean>

</beans>

说一个我的例子,我在Conroller类上加上了@Controller自动注册注释,然后把aop的配置引入放到了applicationContext.xml里,这个配置由ContextLoaderListener读取的

    <import resource="classpath*:spring/aop/aopConfig.xml" />

结果AOP方法就不执行了,解决方法就是需要将aopConfig.xml放到ServletDispatcher的配置xml文件里

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