<?xml?version="1.0"?encoding="UTF-8"?>
<web-app>
??<display-name></display-name>
??<welcome-file-list>
????<welcome-file>index.jsp</welcome-file>
??</welcome-file-list>
??<filter>
??????<filter-name>FirstFilter</filter-name>
??????<filter-class>com.imooc.filter.FirstFilter</filter-class>
??</filter><filter-mapping>
??????<filter-name>FirstFilter</filter-name>
??????<url-pattern>/index.jsp</url-pattern></filter-mapping>
??<!--??
??<filter-mapping>
??????<filter-name>FirstFilter</filter-name>
??????<url-pattern>/main.jsp</url-pattern>
??????<dispatcher>FORWARD</dispatcher></filter-mapping>
??-->
??<!--??
??<filter>
??????<filter-name>SecondFilter</filter-name>
??????<filter-class>com.imooc.filter.SecondFilter</filter-class></filter>
??<filter-mapping>
??????<filter-name>SecondFilter</filter-name>
??????<url-pattern>/index.jsp</url-pattern></filter-mapping>
??-->
??<error-page>
????<error-code>404</error-code>
????<location>/error.jsp</location>
??</error-page>
???????
</web-app>

package?com.imooc.filter;

import?java.io.IOException;

import?javax.servlet.Filter;
import?javax.servlet.FilterChain;
import?javax.servlet.FilterConfig;
import?javax.servlet.ServletException;
import?javax.servlet.ServletRequest;
import?javax.servlet.ServletResponse;
import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;

public?class?FirstFilter?implements?Filter?{

????@Override
????public?void?destroy()?{
????????System.out.println("destory-----FirstFilter");
????}

????@Override
????public?void?doFilter(ServletRequest?request,?ServletResponse?response,?FilterChain?chain)
????????????throws?IOException,?ServletException?{
????????System.out.println("start---FirstFilter--doFilter");
//????????chain.doFilter(request,?response);
????????HttpServletRequest?req?=?(HttpServletRequest)?request;
????????HttpServletResponse?response2?=?(HttpServletResponse)?response;
????????//重定向
????????response2.sendRedirect(req.getContextPath()+"/main.jsp");
????????//轉(zhuǎn)發(fā)
//????????req.getRequestDispatcher("main.jsp").forward(request,?response);
//????????req.getRequestDispatcher("main.jsp").include(request,?response);
????????System.out.println("end---FirstFilter--doFilter");
????}

????@Override
????public?void?init(FilterConfig?filterConfig)?throws?ServletException?{
????????System.out.println("init-----FirstFilter");
????}

}

以上分別是web.xml和FirstFilter的代碼，請(qǐng)大神告知下