servlet过滤器(Filter)详解(九)

时间:2022-04-18 00:46:16

本文实例为大家分享了servlet过滤器的具体代码,供大家参考,具体内容如下

1.servlet过滤器产生背景

  项目中我们会遇到这样一类的需求,对访问服务器的用户ip实施过滤,只有在允许名单中的ip才能访问服务,为了实现需求,每当有客户端请求时,我们都会写校验ip的代码,客户端能够访问到的servlet我们都需要这样做,很明显这样做有一个缺点,就是代码冗余,维护不方便,如果验证规则改变,修改起来也特别麻烦。

  为了解决以上问题,Filter 技术应运而生。

2.servlet过滤器是什么?

  servlet过滤器是在java servlet 2.3 中定义的。它能够对servlet容器传给servlet组件的ServletRequest 对象和 ServletResponse对象进行检查和修改。

3.案例

  所有servlet过滤器都要实现javax.servlet.Filter接口。

NoteFilter

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package com.learn;
 
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
 
/**
 * Created by Administrator on 2017/09/29.
 */
public class NoteFilter implements Filter {
 
 private FilterConfig config = null;
 
 private String ipTable = null; //ip名单
 
 
 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
  System.out.println("note filter initial");
  this.config = filterConfig;
  this.ipTable = config.getInitParameter("ipTable");
 
 }
 
 @Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
  System.out.println("do filter starting");
 
  //校验ip地址
  if(!veryfyIP(request,response))
   return;
 
  long befor = System.currentTimeMillis();
  config.getServletContext().log("before call note Filter");
 
  chain.doFilter(request,response);
 
  config.getServletContext().log("after call note Filter");
  long after = System.currentTimeMillis();
 
  String name ="";
  if(request instanceof HttpServletRequest){
   name = ((HttpServletRequest) request).getRequestURI();
  }
  config.getServletContext().log("Note Filter : name:"+name +" time :"+(after -befor)+"ms");
 
 
 }
 
 @Override
 public void destroy() {
 
 }
 
 private boolean veryfyIP(ServletRequest request, ServletResponse response){
 
  String ip = request.getRemoteAddr();
  System.out.println("请求ip:"+ip);
  System.out.println("ipTable 黑名单:"+ipTable);
 
  if(ip.indexOf(ipTable) == -1){
   System.out.println("校验不通过");
   response.setContentType("text/html");
   PrintWriter out = null;
   try {
    out = response.getWriter();
    out.print("<h1>对不起,你的ip不能访问服务器</h1>");
    out.flush();
    out.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
   return false;
 
  } else {
   return true;
  }
 
 }
 
 
}

NoteServlet

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package com.learn;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
/**
 * Created by Administrator on 2017/09/29.
 */
public class NoteServlet extends HttpServlet {
 
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  System.out.println("已经通过了过滤器");
 
 
 }
}

web.xml配置

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<filter>
  <filter-name>ip</filter-name>
  <filter-class>com.learn.NoteFilter</filter-class>
  <init-param>
   <param-name>ipTable</param-name>
   <param-value>127.0.0.1</param-value>
  </init-param>
 </filter>
 <filter-mapping>
  <filter-name>ip</filter-name>
  <url-pattern>/note</url-pattern>
 </filter-mapping>
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<servlet>
  <servlet-name>note</servlet-name>
  <servlet-class>com.learn.NoteServlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>note</servlet-name>
  <url-pattern>/note</url-pattern>
 </servlet-mapping>

结果如下:

servlet过滤器(Filter)详解(九)

servlet过滤器(Filter)详解(九)

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:http://www.cnblogs.com/wwyx-xi/p/7613011.html