jsp过滤器

1、ip过滤

IpFilter：

package com.cn.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 IpFilter implements Filter {

    private String ip;

    public void destroy() {

    }

    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        System.out.println("ipFilter");

        //获取请求ip

        String clientIp = request.getRemoteAddr();

        System.out.println("ip="+ip);

        System.out.println("clientIp="+clientIp);

        if(!clientIp.equals(ip)){

            chain.doFilter(request, response);

        }else{

            HttpServletRequest req = (HttpServletRequest)request;

            req.getRequestDispatcher("sorry.jsp").forward((HttpServletRequest)request, (HttpServletResponse)response);

        }

    }

    public void init(FilterConfig filterConfig) throws ServletException {

        ip = filterConfig.getInitParameter("ip");

    }

}

web.xml：

  <!-- 配置过滤器 -->

  <filter>

      <filter-name>ipFilter</filter-name>

      <filter-class>com.cn.filter.IpFilter</filter-class>

      <init-param>

          <param-name>ip</param-name>

          <param-value>127.0.0.1</param-value>

      </init-param>

  </filter>

  <filter-mapping>

      <filter-name>ipFilter</filter-name>

      <url-pattern>/*</url-pattern>

  </filter-mapping>

2、统计访问人数

CountFilter：

package com.cn.filter;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

public class CountFilter implements Filter {

    int count = 0;

    //销毁

    public void destroy() {

    }

    //执行

    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        System.out.println("countFilter");

        count++;

        //强转类型

        HttpServletRequest req = (HttpServletRequest)request;

        ServletContext servletContext = req.getSession().getServletContext();

        servletContext.setAttribute("count", count);

        //向下传递请求

        chain.doFilter(request, response);

    }

    //初始化

    public void init(FilterConfig filterConfig) throws ServletException {

        String cou = filterConfig.getInitParameter("count");

        count = Integer.parseInt(cou);

    }

}

CountServlet：

package com.xtkj.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class CountServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        this.doPost(request, response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        ServletContext servletContext = request.getSession().getServletContext();

        Object count = servletContext.getAttribute("count");

        response.setContentType("text/html;charset=gbk");

        PrintWriter out = response.getWriter();

        out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");

        out.println("<HTML>");

        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");

        out.println("  <BODY>");

        out.print("您是第"+count+"位访问该网站的用户！");

        out.println("  </BODY>");

        out.println("</HTML>");

        out.flush();

        out.close();

    }

}

web.xml

  <filter>

      <filter-name>countFilter</filter-name>

      <filter-class>com.cn.filter.CountFilter</filter-class>

      <!-- 配置默认参数 -->

      <init-param>

          <param-name>count</param-name>

          <param-value>3000</param-value>

      </init-param>

  </filter>

  <filter-mapping>

      <filter-name>countFilter</filter-name>

      <url-pattern>/*</url-pattern>

  </filter-mapping>

3、图片防盗（不允许通过地址栏链接打开图片，必须访问index.jsp才能打开图片）

ImgRedirectFilter：

package com.cn.filter;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ImgRedirectFilter implements Filter {

    public void init(FilterConfig filterConfig) throws ServletException {

        //

    }

    public void doFilter(ServletRequest request, ServletResponse response,

            FilterChain chain) throws IOException, ServletException {

        HttpServletRequest req = (HttpServletRequest)request;

        HttpServletResponse resp = (HttpServletResponse)response;

        String referer = req.getHeader("referer");

        if(referer==null || !referer.contains(req.getServerName())){

            req.getRequestDispatcher("-----错误页面").forward(request, response);

        }else{

            chain.doFilter(req, resp);

        }

    }

    public void destroy() {

        //

    }

}

ImgServlet：

package com.cn.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ImgServlet extends HttpServlet {

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

        this.doPost(request, response);

    }

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

        String name = request.getParameter("name");

        request.getRequestDispatcher("img/"+name).forward(request, response);

    }

}

web.xml：

  <filter>

      <filter-name>ImgRedirectFilter</filter-name>

      <filter-class>com.cn.filter.ImgRedirectFilter</filter-class>

  </filter>

  <filter-mapping>

      <filter-name>ImgRedirectFilter</filter-name>

      <url-pattern>*.jpg</url-pattern>

  </filter-mapping>

index.jsp：

  <body>

    <img src="img/img01.jpg" /><a href="ImgServlet?name=img01.jpg">头像1</a></abbr><br/>

    <img src="img/img02.jpg" /><a href="ImgServlet?name=img02.jpg">头像2</a><br/>

    <img src="img/img03.jpg" /><a href="ImgServlet?name=img03.jpg">头像3</a><br/>

  </body>

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