J2EE-Servlet過濾器

<!-- 聲明 -->
  <filter>
  	<filter-name>Myfilter</filter-name>
  	<filter-class>com.pas.controller.MyFilter</filter-class>
  </filter>
  <!-- 映射 -->
  <filter-mapping>
  	<filter-name>Myfilter</filter-name>
  	<url-pattern>/*</url-pattern>  
  </filter-mapping>

關於URL pattern參考

若是有多個filter 執行順序按照xml中配置順序

過濾器實例：

package com.pas.controller; import java.io.IOException; import java.io.PrintWriter; 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.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.pas.domain.User; public class MyFilter extends HttpServlet implements Filter { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=gb2312"); PrintWriter out = response.getWriter(); out.flush(); out.close(); } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpServletRequest req=(HttpServletRequest)request; //查看請求資源 String url=req.getRequestURI(); if (url.startsWith("/UserManager/CreateCode") || url.startsWith("/UserManager/Login") || url.startsWith("/UserManager/imgs")) { //放行 chain.doFilter(request, response); } else { HttpSession session = req.getSession(); User u = (User) session.getAttribute("User"); if (u != null) { chain.doFilter(request, response); } else { request.setAttribute("err", "請登陸,過濾器攔截"); request.getRequestDispatcher("/LoginServlet").forward(request, response); } } } public void init(FilterConfig arg0) throws ServletException { // TODO Auto-generated method stub } }