ContextLoaderListener 與 ServletDispatcher

網上找了一下關於ContextLoaderListener和ServletDispatcher的解釋,這是原文

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

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

總結如下:

Spring中有兩種上下文環境-"Application Context和Web Application Context",他們分別對應ContextLoaderListener和ServletDispatcher,且都可以用來配置bean的注入,裝配,和AOP

1. ContextLoaderListener

ContextLoaderListener通過讀取contextConfigLocation參數來讀取配置參數,一般來說它配置的是Spring項目的中間層,服務層組件的注入,裝配,AOP.

對應到Spring的自動裝配機制<context:component-scan>就是以下幾種注解的裝配

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

(以上內容來自引用博文)

下面是一個典型web.xml中加載ContextLoaderListener的代碼片段

    <!-- 定義參數 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath*:spring/config/applicationContext.xml</param-value>
    </context-param>

    <!-- 定義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的配置文件都是中間層,數據層,DAO之類的

2. ServletDispatcher

ServletDispatcher通過讀取<servlet-name>-servlet.xml文件來讀取配置,如果文件不存在,則可以通過servlet標簽內的

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

來指定配置文件,它配置的是Web層組件的注入,裝配和AOP

• Controllers
• ViewResolvers
• LocaleResolvers
• ThemeResolvers

下面是一個典型配置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>

 

說一個我的例子,我在Conroller類上加上了@Controller自動注冊注釋,然后把aop的配置引入放到了applicationContext.xml里,這個配置由ContextLoaderListener讀取的

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

結果AOP方法就不執行了,解決方法就是需要將aopConfig.xml放到ServletDispatcher的配置xml文件里