过滤器-->GZIP压缩

1.创建一个 可以使用GZIPOutputStream 压缩的流

package com.zh.yasuo2;

import java.io.IOException;
import java.util.zip.GZIPOutputStream;

import javax.servlet.ServletOutputStream;

public class GzipServletOupputStream extends ServletOutputStream{

 private GZIPOutputStream gzipOutputStream;
 @Override
 public void write(int b) throws IOException {
  // TODO Auto-generated method stub
  System.out.println("b="+b);
  gzipOutputStream.write(b);
 }

 public GzipServletOupputStream(ServletOutputStream servletOutPutStream) throws IOException{
  this.gzipOutputStream=new GZIPOutputStream(servletOutPutStream);
 }

 public GZIPOutputStream getGZIPOutputStream(){
  return gzipOutputStream;
 }
}

2. 继承 HttpServletResponseWrapper 重写 getOutputStream(),  getWriter()方法.  使其流是可以压缩的

package com.zh.yasuo2;

import java.io.*;
import java.util.zip.GZIPOutputStream;
import javax.servlet.*;
import javax.servlet.http.*;

public class GzipWrapper extends HttpServletResponseWrapper{

 private GzipServletOupputStream gzipServletOupputStream;
 private PrintWriter printwrite;
 public GzipWrapper(HttpServletResponse response) {
  super(response);
  // TODO Auto-generated constructor stub
 }
 //重写 getOutputStream()方法
 public ServletOutputStream getOutputStream()throws IOException{
  if(printwrite != null){
   throw new IllegalStateException();
  }

  if(gzipServletOupputStream ==null){
   gzipServletOupputStream=new GzipServletOupputStream(this.getResponse().getOutputStream());
  }

  return gzipServletOupputStream;
 }

 //重写getWriter()方法
 public PrintWriter getWriter() throws IOException{
  if(gzipServletOupputStream != null){
   throw new IllegalStateException();
  }
  if(printwrite== null){
   gzipServletOupputStream=new GzipServletOupputStream(this.getResponse().getOutputStream());
   OutputStreamWriter osw=new OutputStreamWriter(gzipServletOupputStream,getResponse().getCharacterEncoding());
   printwrite=new PrintWriter(osw);
   //System.out.println("printwrite"+printwrite.toString());
  }
  return printwrite;
 }

 public void setContentLength(int len){

 }

 public GZIPOutputStream getGZIPOutputStream(){
  if(this.gzipServletOupputStream == null){
   return null;
  }
  return this.gzipServletOupputStream.getGZIPOutputStream();
 }
}

3.使用过滤器

package com.zh.yasuo2;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;
import javax.servlet.*;
import javax.servlet.http.*;
public class GzipFilter implements Filter{

 public void destroy() {
  // TODO Auto-generated method stub

 }

 public void doFilter(ServletRequest arg0, ServletResponse arg1,
   FilterChain arg2) throws IOException, ServletException {
  // TODO Auto-generated method stub
  HttpServletRequest req=(HttpServletRequest) arg0;
  HttpServletResponse res=(HttpServletResponse) arg1;
  //用encodings 来判断浏览器是否有 gzip压缩的功能
  String encodings=req.getHeader("accept-encoding");

  if((encodings!=null) && (encodings.indexOf("gzip"))>-1){
   GzipWrapper gzipWrapper=new GzipWrapper(res);
   //设置响应内容编码为gzip格式
   gzipWrapper.setHeader("content-encoding", "gzip");
   arg2.doFilter(arg0, gzipWrapper);
   GZIPOutputStream gzipOutputStream=gzipWrapper.getGZIPOutputStream();
   if(gzipOutputStream !=null ){
    gzipOutputStream.finish();  //写成压缩输出
    System.out.println("finish();");
   }
  }else{
   arg2.doFilter(arg0, arg1);
  }
 }

 public void init(FilterConfig arg0) throws ServletException {
  // TODO Auto-generated method stub

 }
}

4.web.xml

<filter>
   <filter-name>GzipFilter</filter-name>
   <filter-class>com.zh.yasuo2.GzipFilter</filter-class>
  </filter>
  <filter-mapping>
   <filter-name>GzipFilter</filter-name>
   <url-pattern>/GzipServler</url-pattern>
  </filter-mapping>

5. servlet 实验.

package com.zh.yasuo2;

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 GzipServler extends HttpServlet {

 /**
  * The doGet method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to get.
  *
  * @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 doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("text/html;charset=utf-8");
  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 GET method");
  out.println("  </BODY>");
  out.println("</HTML>");
  out.flush();
  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
    .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();
 }

}