JavaWeb项目过滤器的编写

一、字符过滤器

（1）Java class编写：

package com.struts2.project.util.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;

public class CharacterFilter implements Filter{
 private static String character=null;

 public void destroy() {
  
 }

 public void doFilter(ServletRequest req, ServletResponse res,
   FilterChain fch) throws IOException, ServletException {
  req.setCharacterEncoding(character);
  res.setCharacterEncoding(character);
  fch.doFilter(req, res);
  
 }

 @SuppressWarnings("static-access")
 public void init(FilterConfig config) throws ServletException {
  this.character=config.getInitParameter("character");
  if(this.character==null){
   throw new RuntimeException("提示：not found parameter named character");
  }
  
 }

}

（2）web.xml文件

<filter>
   <filter-name>character</filter-name>
   <filter-class>com.struts2.project.util.filter.CharacterFilter</filter-class>
   <init-param>
      <param-name>character</param-name>
      <param-value>UTF-8</param-value>
   </init-param>
</filter>
<filter-mapping>
    <filter-name>character</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

（3）jsp页面字符编码：pageEncoding="UTF-8";

二、session过滤器

（1）Java class编写：

publicclass FilterDemo implements Filter{

    publicvoid destroy() {}

    publicvoid doFilter(ServletRequest sreq, ServletResponse response,FilterChain filterChain)

                       throws IOException, ServletException {

       HttpServletRequest request=(HttpServletRequest)sreq;

       HttpSession session = request.getSession(false);

       if(session == null) {

           //如果是session超时，在此处做处理
       }

       if(request.getRequestURI().endsWith("download.do")) {

           //此处可以针对不同的请求根据用户是否具有权限来做处理
       }

       request.getRequestDispatcher("/Error.jsp").forward(request,response);

    }

    publicvoid init(FilterConfig filterConfig) throws ServletException {}

}

然后将新建的Filter添加到web.xml中，部署Filter需要添加两部分：

(2)web.xml文件

filter元素位于部署描述符文件（web.xml）的前部，所有filter-mapping、servlet或servlet-mapping元素之前。

 <filter>
       <filter-name>SessionFilter</filter-name>
       <filter-class>myPackage.FilterDemo</filter-class>
</filter>

<filter-mapping>
       <filter-name>SessionFilter</filter-name>
       <url-pattern>*.do</url-pattern>
</filter-mapping>

以上内容表示所以的请求中以.do结尾的都有首先通过我们这里指定的过滤器：

(3)Servlet来测试：

publicclass DownLoadDemo extends HttpServlet {

     privatestaticfinallongserialVersionUID = 1L;

     public DownLoadDemo() {

        super();

    }

protectedvoid doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

       this.doPost(request, response);

    }

protectedvoid doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

       request.getRequestDispatcher("/DownLoadExcel.jsp").

forward(request, response);

    }

}

在web.xml中部署好该servlet

<servlet>

       <servlet-name>DownLoadDemo</servlet-name>

       <servlet-class>com.sinosoft.base.sessiondemo.DownLoadDemo</servlet-class>

    </servlet>

    <servlet-mapping>

       <servlet-name>DownLoadDemo</servlet-name>

       <url-pattern>/download</url-pattern>

    </servlet-mapping>

新建jsp来测试index.jsp

<body>

    <form action="download.do">

 <a href = 'DownLoadExcel.jsp'>导出Excel</a>

    <input type='submit'/>

    </form>

</body>

使用一个是超链接的形式，一个是通过servlet来跳转，当点击提交按钮时会被拦截，而直接点击超链接就不会被拦截，因为我们的Filter中配置的是拦截.do形式的，如果要拦截jsp也可以使用<url-pattern>DownLoadExcel.jsp </url-pattern>

再添加一个错误页面Error.jsp

<body>

<h1>对不起，你没有权限</h1>

</body>

三、用户浏览权限过滤

（1）Java class编写：

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;    
   
public class RightFilter implements Filter {    
   
    public void destroy() {    
            
     }    
    public void doFilter(ServletRequest sreq, ServletResponse sres, FilterChain arg2) throws IOException, ServletException {    
        // 获取uri地址    
         HttpServletRequest request=(HttpServletRequest)sreq;    
         String uri = request.getRequestURI();    
         String ctx=request.getContextPath();    
         uri = uri.substring(ctx.length());    
         //判断admin级别网页的浏览权限    
         if(uri.startsWith("/admin")) {    
            if(request.getSession().getAttribute("admin")==null) {    
                 request.setAttribute("message","您没有这个权限");    
                 request.getRequestDispatcher("/login.jsp").forward(sreq,sres);    
                return;    
             }    
         }    
        //判断manage级别网页的浏览权限    
        if(uri.startsWith("/manage")) {    
            //这里省去    
             }    
         }    
        //下面还可以添加其他的用户权限，省去。    
   
     }    
   
    public void init(FilterConfig arg0) throws ServletException {    
            
     }    
   
}

（2）在web.xml中加入Filter的配置，如下：

<!-- 判断页面的访问权限 -->   
  <filter>   
     <filter-name>RightFilter</filter-name>   
      <filter-class>cn.itkui.filter.RightFilter</filter-class>   
  </filter>   
  <filter-mapping>   
      <filter-name>RightFilter</filter-name>   
      <url-pattern>/admin/*</url-pattern>   
  </filter-mapping>   
  <filter-mapping>   
      <filter-name>RightFilter</filter-name>   
      <url-pattern>/manage/*</url-pattern>   
  </filter-mapping>

posted on 2011-07-27 16:48 boonya 阅读(839) 评论(0) 编辑收藏举报