简介
web.xml是web工程的配置文件，容器加载web工程时，会首先从WEB-INF中查询web.xml，并加载其中的配置信息，可以将web.xml认为是web工程的入口。
web.xml中包含有welcome欢迎页面、servlet、servlet-mapping、filter、listener和启动加载级别等。
web.xml加载顺序
- 容器读取工程的配置文件web.xml，读取<listener>和<context-param>两个节点。
- 容器创建ServletContext，所有的web项目都将共享该ServletContext。
- 容器将<context-param>转换为键值对，并交给ServletContext。
- 容器创建<listener>中的类的实例，创建监听器
web.xml内容详解
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:web="http://java.sun.com/xml/ns/javaee" xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<display-name>console</display-name>
<!--servletContext加载的属性信息 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring.xml,classpath:spring-mybatis.xml,classpath:spring-shiro.xml</param-value>
</context-param>
<!-- 定义过滤器的名称，以及其初始化参数-->
<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>
</filter>
<!-- 定义url被哪个filter过滤，下面的配置表示所有的请求都必须经过shiroFilter -->
<filter-mapping>
<filter-name>shiroFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter>
<filter-name>ResponseCrossFilter</filter-name>
<filter-class>com.emcc.changedig.filter.ResponseCrossFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>ResponseCrossFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- 定义监听器，控制容器在启动和停止时的行为 -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<filter>
<filter-name>encodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<description>字符集编码</description>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- 清理监听器，当应用停止时，使用该listener释放资源 -->
<listener>
<listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class>
</listener>
<! – 定义servlet，初始化参数以及启动顺序 -->
<servlet>
<description>spring mvc servlet</description>
<servlet-name>springMvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<description>spring mvc 配置文件</description>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>DruidStatView</servlet-name>
<servlet-class>com.alibaba.druid.support.http.StatViewServlet</servlet-class>
<init-param>
<!-- 允许清空统计数据 -->
<param-name>resetEnable</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<!-- 用户名 -->
<param-name>loginUsername</param-name>
<param-value>druid</param-value>
</init-param>
<init-param>
<!-- 密码 -->
<param-name>loginPassword</param-name>
<param-value>druid</param-value>
</init-param>
</servlet>
<!-- 定义servlet 映射规则 -->
<servlet-mapping>
<servlet-name>DruidStatView</servlet-name>
<url-pattern>/druid/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>springMvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<session-config>
<!-- 时间单位是分钟 -->
<session-timeout>360</session-timeout>
</session-config>
<!-- default表示，对客户端请求的静态资源，交由默认的servlet来处理 -->
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.css</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.js</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.ico</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.gif</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.jpg</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.png</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.bmp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.jpeg</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.swf</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.flv</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.xml</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.txt</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.htm</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.html</url-pattern>
</servlet-mapping>
<!-- 定义错误返回页面 -->
<error-page>
<error-code>404</error-code>
<location>/web/error/404.html</location>
</error-page>
</web-app>