JSP学习笔记——过滤器（二）使用

过滤器的使用：

1.       过滤非法文字

package demo.filter ;   import java.io.* ; import javax.servlet.* ; import javax.servlet.http.* ;   public class CharFilter implements Filter {        public void init(FilterConfig filterConfig)throws ServletException        {               System.out.println("**Filter初始化……") ;        }            public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws java.io.IOException,ServletException        {               request.setCharacterEncoding("gbk") ;               String name = request.getParameter("name") ;               if(name!=null){                      if(name.indexOf("猪猪")==-1){                            chain.doFilter(request,response) ;                      }else{                             System.out.println("非法字符！") ;                      }               }else{                      System.out.println("feikong") ;               chain.doFilter(request,response) ;               }        }        public void destroy(){} }

2.       对内容进行统一编码

package demo.filter ;   import java.io.* ; import javax.servlet.* ; import javax.servlet.http.* ;   public class EncodingFilter implements Filter {        public void init(FilterConfig filterConfig)throws ServletException        {}           public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws java.io.IOException,ServletException        {               try               {                      request.setCharacterEncoding("gb2312") ;               }               catch (Exception e)       {}               chain.doFilter(request,response) ;        }        public void destroy()        {} }

3.       登录验证

package demo.filter ;   import java.io.* ; import javax.servlet.* ; import javax.servlet.http.* ;   public class SessionFilter implements Filter {        public void init(FilterConfig filterConfig)throws ServletException        {}           public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws java.io.IOException,ServletException        {               HttpServletRequest req = (HttpServletRequest)request ;               HttpServletResponse res = (HttpServletResponse)response ;               HttpSession session = req.getSession() ;               System.out.println(session.getAttribute("name")) ;               if (session.getAttribute("name")!=null)               {                      //System.out.println("已登录……") ;                      chain.doFilter(request,response) ;               }else{                      //System.out.println("未登录……") ;                      request.getRequestDispatcher("login.jsp").forward(request,response) ;               }             }        public void destroy()        {} }