context-param、init-param、监听器、过滤器与拦截器

本文详细解析了Servlet配置中的context-param、init-param、监听器、过滤器和拦截器的区别及作用。context-param作为全局变量,适用于所有servlet;init-param为局部变量,仅限于声明的servlet使用;监听器用于监控项目运行时属性,如在线人数统计;过滤器作用于servlet之前,统一处理字符集等;拦截器则作用于servlet内部,如登录认证。

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1.context-param 相当于全局变量,针对容器中所有的servlet都有效,均可获取该参数,与监听器无任何必然关系,紧设置的参数可在监听器中监控使用而已;

2.init-param相当于局部变量,只针对在xml中声明的servlet中有效;

3.监听器Listener:监听整个项目运行时的相关属性,可从request、session、application中获取相关属性   eg:统计在线聊天人数、系统正在使用人数等

4.过滤器filter:作用于servlet之前,对整个请求操作执行相关操作  eg:统一入参字符集

5.拦截器:作用于servlet之中,可作用与controller、service之前等,主要对相关请求进行拦截处理  eg:登录认证

 

加载顺序:

context-param ====》 监听器 =====》 过滤器  =====》 拦截器

 

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <display-name></display-name> <context-param> <param-name>contextConfigLocation</param-name> <param-value> classpath*:applicationContext*.xml classpath*:*Context.xml </param-value> </context-param> <context-param> <param-name>webAppRootKey</param-name> <param-value>rms.root</param-value> </context-param> <context-param> <param-name>log4jConfigLocation</param-name> <param-value>/WEB-INF/classes/log4j.properties</param-value> </context-param> <context-param> <param-name>log4jRefreshInterval</param-name> <param-value>60</param-value> </context-param> <listener> <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class> </listener> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <listener> <listener-class>com.hg.filter.UrlAuthListen</listener-class> </listener> <listener> <listener-class>com.hg.filter.WebConfigListener</listener-class> </listener> <filter> <filter-name>openSessionInViewFilter</filter-name> <filter-class>org.springframework.orm.hibernate4.support.OpenSessionInViewFilter </filter-class> <init-param> <param-name>singleSession</param-name> <param-value>true</param-value> </init-param> </filter> <filter-mapping> <filter-name>openSessionInViewFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <filter> <filter-name>XssFilter</filter-name> <filter-class>com.hg.aop.XssFilter</filter-class> </filter> <filter-mapping> <filter-name>XssFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- dwr 配置 --> <servlet> <servlet-name>dwr-invoker</servlet-name> <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class> <init-param> <param-name>debug</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>activeReverseAjaxEnabled</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>crossDomainSessionSecurity</param-name> <param-value>false</param-value> </init-param> <init-param> <description>How quickly do scriptSessions timeout?</description> <param-name>scriptSessionTimeout</param-name> <param-value>1800000</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>dwr-invoker</servlet-name> <url-pattern>/dwr/*</url-pattern> </servlet-mapping> <listener> <listener-class>org.directwebremoting.servlet.EfficientShutdownServletContextAttributeListener</listener-class> </listener> <!-- dwr 配置 --> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>具体解释一下web.xml的配置
最新发布
07-08
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