过滤字符功能

1.重写HttpServletRequest子类

package com.zh.charFilter;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class CharRequestWrapper extends HttpServletRequestWrapper{
 private Map<String,String> escapeMap=null;
 
 public CharRequestWrapper(HttpServletRequest request) {
  super(request);
  // TODO Auto-generated constructor stub
 }
 //重新写了这个构造方法
 public CharRequestWrapper(HttpServletRequest arg0,Map<String,String> escapeMap) {
  super(arg0);
  this.escapeMap=escapeMap;
  // TODO Auto-generated constructor stub
 }
 
 public String getParameter(String name){
  //System.out.println("CharRequestWrapper getParmeter");
  return this.doEscape(this.getRequest().getParameter(name));
 }
 
 //把收到的 parmeter 中的一些字符 替换
 //Map("要替换的","被替换的") 例: Map("<","&lt;");
 private String doEscape(String parmeter){
  if(parmeter==null){
   return null;
  }
  
  String result=parmeter;
  Iterator<String> iterator=escapeMap.keySet().iterator();
  while(iterator.hasNext()){
   String origin=iterator.next();
   String escape=escapeMap.get(origin);
   result=result.replaceAll(origin, escape);
  }
  
  return result;
 }
 
}



2.使用过滤器

package com.zh.charFilter;

import java.io.*;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;

public class CharFilter implements Filter{
 
 private Map<String,String> escapeMap=null;
 
 public void doFilter(ServletRequest arg0, ServletResponse arg1,
   FilterChain arg2) throws IOException, ServletException {
  // TODO Auto-generated method stub
  HttpServletRequest httpServletWrapper=new CharRequestWrapper((HttpServletRequest)arg0,escapeMap);
  //System.out.println("getParameter="+httpServletWrapper.getParameter("<input>"));
  arg2.doFilter(httpServletWrapper, arg1);
 }
 
 //将要替换的渗格式 写入Map中
 public void init(FilterConfig arg0) throws ServletException {
  // TODO Auto-generated method stub
  BufferedReader bufferedReader=null;
  
  try {
   bufferedReader=new BufferedReader(new FileReader(arg0.getServletContext().getRealPath("/MyFile/charFiter.txt")));
   String input=null;
   escapeMap=new HashMap<String,String>();
   while( (input = bufferedReader.readLine()) != null){
    String[] tokens=input.split("	");
    escapeMap.put(tokens[0], tokens[1]);
   }
   
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }finally{
   try {
    bufferedReader.close();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
 }
 
 public void destroy() {
  // TODO Auto-generated method stub
  
 }
}



3. 过滤的servlet view

package com.zh.charFilter;

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;

public class CharServlet extends HttpServlet{

 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  response.setContentType("text/html;charset=utf-8");
  PrintWriter out = response.getWriter();
  out.println("<form action='/MyFilter/CharServlet2' method='get'>");
  out.println("<textarea rows='3' name='textarea' cols='30'>");
  out.println("</textarea>");
  out.println("<input type='submit'/>");
  out.println("</form>");
  out.close();
 }

 /**
  * The doPost method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to post.
  * 
  * @param request the request send by the client to the server
  * @param response the response send by the server to the client
  * @throws ServletException if an error occurred
  * @throws IOException if an error occurred
  */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("text/html");
  PrintWriter out = response.getWriter();

  out.close();
 }

}



4. 过滤的结果 

package com.zh.charFilter;

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 CharServlet2 extends HttpServlet {


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

  response.setContentType("text/html");
  PrintWriter out = response.getWriter();
  out.println("<h1>ni hao</h1>");
  String s=request.getParameter("textarea");
  //System.out.println(s);
  out.println(s);
  out.close();
 }


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

  response.setContentType("text/html");
  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("    This is ");
  out.print(this.getClass());
  out.println(", using the POST method");
  out.println("  </BODY>");
  out.println("</HTML>");
  out.flush();
  out.close();
 }

}



5.  要过滤的字符 和 文件

<　　&lt;
>　　&gt;

charFiter.txt



6.设置web.xml

<filter>
   <filter-name>CharFilter</filter-name>
   <filter-class>com.zh.charFilter.CharFilter</filter-class>
  </filter>
  <filter-mapping>
   <filter-name>CharFilter</filter-name>
   <url-pattern>/CharServlet2</url-pattern>
  </filter-mapping>