全站压缩代---练习代码

package com.elomo.filter;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
//全站压缩过滤器
public class GzipFilter implements Filter {

	public void init(FilterConfig filterConfig) throws ServletException {

	}

	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest)req;
		HttpServletResponse response =(HttpServletResponse)res;
		//包装response，将输出流存到缓存中用
		GzipHttpServletResponse gresponse = new GzipHttpServletResponse(response);
		chain.doFilter(request, gresponse);
		//这里是压缩代码
		//找到一个内存缓冲字节流
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		//把数据压缩到字节缓冲流中
		GZIPOutputStream gout = new GZIPOutputStream(baos);
		//取出数据，压缩后的
		byte[] b= gresponse.getOldBytes();
		System.out.println("原始数据大小："+b.length);
		gout.write(b);
		gout.close();//保证所有的数据都进字节缓冲流中。
		
		//取出压缩后的数据
		b = baos.toByteArray();
		System.out.println("压缩数据大小："+b.length);
		//通知客户端压缩方式
		response.setHeader("Content-Encoding", "gzip");
		response.setContentLength(b.length);
		//服务器的响应输出
		ServletOutputStream out = response.getOutputStream();
		out.write(b);
		
		
		
	}

	public void destroy() {

	}

}

class GzipHttpServletResponse extends HttpServletResponseWrapper{
	private ByteArrayOutputStream baos= new ByteArrayOutputStream();
	private PrintWriter pw;
	public GzipHttpServletResponse(HttpServletResponse response) {
		super(response);
	}

	//把原始数据存放到一个缓冲流中
	@Override
	public ServletOutputStream getOutputStream() throws IOException {
		return new MyServletOutputStream(baos);
	}
	
	
	//字符流：把原始的数据封装到一个缓冲流中
	@Override
	public PrintWriter getWriter() throws IOException {
		pw = new PrintWriter(new OutputStreamWriter(baos,super.getCharacterEncoding()));
		return pw;
	}

	// 返回baos中的缓冲数据：原始
	public byte[] getOldBytes(){
		try {
			if(pw!=null)
				pw.close();
			baos.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return baos.toByteArray();
	}
}

class MyServletOutputStream extends ServletOutputStream{
	private ByteArrayOutputStream baos;
	public MyServletOutputStream(ByteArrayOutputStream baos){
		this.baos = baos;
	}
	@Override
	public void write(int b) throws IOException {
		baos.write(b);
	}
	
}

最后，不要忘记在web.XML中配置一下哈！