修改前運行報錯:No WebApplicationContext found: no ContextLoaderListener registered?
<web-app> <display-name>Archetype Created Web Application</display-name> <filter> <filter-name>CharacterEncodingFilter</filter-name> <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> <!-- <init-param> --> <!-- <param-name>forceEncoding</param-name> --> <!-- <param-value>true</param-value> --> <!-- </init-param> --> </filter> <filter-mapping> <filter-name>CharacterEncodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- 配置shiro 過濾器 --> <filter> <filter-name>shiroFilter</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> <init-param> <param-name>targetFilterLifecycle</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>targetBeanName</param-name> <param-value>shiroFilter</param-value> </init-param> </filter> <filter-mapping> <filter-name>shiroFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- 配置springMVC核心控制器 --> <servlet> <servlet-name>DispatcherServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring_config.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>DispatcherServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping>
<welcome-file-list> <welcome-file>login.jsp</welcome-file> </welcome-file-list> <!-- 配置錯誤頁面 --> <error-page> <error-code>404</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> <error-page> <error-code>500</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> <error-page> <error-code>503</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> <error-page> <error-code>400</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> </web-app>
修改后:
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd" > <web-app> <display-name>web</display-name> <filter> <filter-name>CharacterEncodingFilter</filter-name> <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> <!-- <init-param> --> <!-- <param-name>forceEncoding</param-name> --> <!-- <param-value>true</param-value> --> <!-- </init-param> --> </filter> <filter-mapping> <filter-name>CharacterEncodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- 配置shiro 過濾器 --> <filter> <filter-name>shiroFilter</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> <init-param> <param-name>targetFilterLifecycle</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>targetBeanName</param-name> <param-value>shiroFilter</param-value> </init-param> </filter> <filter-mapping> <filter-name>shiroFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <context-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring_config.xml</param-value> </context-param> <!-- 配置springMVC核心控制器 --> <servlet> <servlet-name>DispatcherServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring_mvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>DispatcherServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>login.jsp</welcome-file> </welcome-file-list> <!-- 配置錯誤頁面 --> <error-page> <error-code>404</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> <error-page> <error-code>500</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> <error-page> <error-code>503</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> <error-page> <error-code>400</error-code> <location>/WEB-INF/jsp/common/error.jsp</location> </error-page> </web-app>
原因分析：
項目加載的shiro過濾器的功能需要依賴ContextLoaderListener所加載的apring_config.xml文件生成的applicationContext即Spring的上下文，而之前DispatcherServlet所加載的spring_mvc.xml文件生成的applicationContext為Spring mvc的上下文，shiro過濾器無法加載，所以得依靠監聽器加載public的applicationContext。
三個context之間的的關系：
- 對於一個web應用，web容器加載一個全局context（即servletContext）供其使用，為后面的spring IoC容器提供依賴。
- 在web.xml中提供的ContextLoaderListener監聽器，web容器啟動時會觸發容器初始化事件，ContextLoaderListener會監聽這個事件，初始化一個根上下文即WebApplicationContext，實現類為XmlWebApplicationContext。這個就是Spring的IoC容器，spring將其以WebApplicationContext.ROOTWEBAPPLICATIONCONTEXTATTRIBUTE為key存儲在servletContext中
- DispatcherServlet在初始化會建立自己的IoC容器用以持有Spring mvc相關的bean，它在建立的時候會通過WebApplicationContext.ROOTWEBAPPLICATIONCONTEXTATTRIBUTE先從servletContext中獲取根上下文作為自己上下文的父上下文，它的實現類也是XmlWebApplicationContext，在建立之后會以和自己servlet-name便簽有關的名稱存儲在servletContext中，這樣每個servlet就擁有自己獨立的bean及根上下文共享的bean
但是這樣會導致重復加載配置文件，DispatcherServlet、ContextLoaderListener會分別加載一次，解決方法是把配置文件拆分成2個，一個Spring mvc的配置文件，一個Spring的配置文件，DispatcherServlet加載Spring mvc的配置文件，ContextLoaderListener加載Spring的配置文件 。
Spring mvc在使用上下文的時候會使用DispatcherServlet加載的applicationContext，也會使用的contextLoaderListener加載的applicationContext。