除了。下面的第9，10条，没用，其他的都在项目里有用到。。。。。。。。
先看各个配置都是干嘛的：
1、Web应用图标：指出IDE和GUI工具用来表示Web应用的大图标和小图标
<icon>
<small-icon>/images/app_small.gif</small-icon>
<large-icon>/images/app_large.gif</large-icon>
</icon>
2、Web 应用名称：提供GUI工具可能会用来标记这个特定的Web应用的一个名称
<display-name>Tomcat Example</display-name>
3、Web 应用描述： 给出于此相关的说明性文本
<disciption>Tomcat Example servlets and JSP pages.</disciption>
4、上下文参数：声明应用范围内的初始化参数。
<context-param>
<param-name>ContextParameter</para-name>
<param-value>test</param-value>
<description>It is a test parameter.</description>
</context-param>
在servlet里面可以通过getServletContext().getInitParameter("context/param")得到
5、过滤器配置：将一个名字与一个实现javaxs.servlet.Filter接口的类相关联。
<filter>
<filter-name>setCharacterEncoding</filter-name>
<filter-class>com.myTest.setCharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>GB2312</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>setCharacterEncoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
6、监听器配置
<listener>
<listerner-class>listener.SessionListener</listener-class>
</listener>
7、Servlet配置
基本配置
<servlet>
<servlet-name>snoop</servlet-name>
<servlet-class>SnoopServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>snoop</servlet-name>
<url-pattern>/snoop</url-pattern>
</servlet-mapping>
高级配置
<servlet>
<servlet-name>snoop</servlet-name>
<servlet-class>SnoopServlet</servlet-class>
<init-param>
<param-name>foo</param-name>
<param-value>bar</param-value>
</init-param>
<run-as>
<description>Security role for anonymous access</description>
<role-name>tomcat</role-name>
</run-as>
</servlet>
<servlet-mapping>
<servlet-name>snoop</servlet-name>
<url-pattern>/snoop</url-pattern>
</servlet-mapping>
元素说明
<servlet></servlet> 用来声明一个servlet的数据，主要有以下子元素：
<servlet-name></servlet-name> 指定servlet的名称
<servlet-class></servlet-class> 指定servlet的类名称
<jsp-file></jsp-file> 指定web站台中的某个JSP网页的完整路径
<init-param></init-param> 用来定义参数，可有多个init-param。在servlet类中通过getInitParamenter(String name)方法访问初始化参数
<load-on-startup></load-on-startup>指定当Web应用启动时，装载Servlet的次序。
当值为正数或零时：Servlet容器先加载数值小的servlet，再依次加载其他数值大的servlet.
当值为负或未定义：Servlet容器将在Web客户首次访问这个servlet时加载它
<servlet-mapping></servlet-mapping> 用来定义servlet所对应的URL，包含两个子元素
<servlet-name></servlet-name> 指定servlet的名称
<url-pattern></url-pattern> 指定servlet所对应的URL
8、会话超时配置（单位为分钟）
<session-config>
<session-timeout>120</session-timeout>
</session-config>
9、MIME类型配置
<mime-mapping>
<extension>htm</extension>
<mime-type>text/html</mime-type>
</mime-mapping>
10、指定欢迎文件页配置
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
</welcome-file-list>
11、配置错误页面
一、 通过错误码来配置error-page
<error-page>
<error-code>404</error-code>
<location>/NotFound.jsp</location>
</error-page>
上面配置了当系统发生404错误时，跳转到错误处理页面NotFound.jsp。
二、通过异常的类型配置error-page
<error-page>
<exception-type>java.lang.NullException</exception-type>
<location>/error.jsp</location>
</error-page>
上面配置了当系统发生java.lang.NullException（即空指针异常）时，跳转到错误处理页面error.jsp
12、TLD配置
<taglib>
<taglib-uri>http://jakarta.apache.org/tomcat/debug-taglib</taglib-uri>
<taglib-location>/WEB-INF/jsp/debug-taglib.tld</taglib-location>
</taglib>
如果MyEclipse一直在报错,应该把<taglib> 放到 <jsp-config>中
<jsp-config>
<taglib>
<taglib-uri>http://jakarta.apache.org/tomcat/debug-taglib</taglib-uri>
<taglib-location>/WEB-INF/pager-taglib.tld</taglib-location>
</taglib>
</jsp-config>
然后上自己实际用的实例代码：
<?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"
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>Web Application</display-name>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/config/applicationContext.xml</param-value>
</context-param>
<context-param>
<param-name>log4jRefreshInterval</param-name>
<param-value>600000</param-value>
</context-param>
<filter>
<filter-name>encodingFilter</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>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<listener>
<listener-class>com.xxx.xxx.utils.listener.StartupListener</listener-class>
</listener>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/config/dispatcher-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>120</session-timeout>
</session-config>
<jsp-config>
<taglib>
<taglib-uri>authorization</taglib-uri>
<taglib-location>/WEB-INF/tlds/authorization.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>messagefield</taglib-uri>
<taglib-location>/WEB-INF/tlds/message.tld</taglib-location>
</taglib>
</jsp-config>
<error-page>
<error-code>400</error-code>
<location>/error/400.jsp</location>
</error-page>
<error-page>
<error-code>404</error-code>
<location>/error/404.jsp</location>
</error-page>
<error-page>
<error-code>405</error-code>
<location>/error/405.jsp</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/error/500.jsp</location>
</error-page>
</web-app>
