使用包装模式进行GZIP数据压缩过滤

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
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;

public class GzipFilter implements Filter {

	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) res;
		
		ByteArrayOutputStream bout=new ByteArrayOutputStream();
		MyResponse myresponse=new MyResponse(response);
		chain.doFilter(request, myresponse);
		
		byte data[]=myresponse.getData();
		System.out.println("原始大小："+data.length);
		
		byte[] gzip=gzip(data);
		response.setHeader("content-encoding", "gzip");
		response.setHeader("content-length", gzip.length+"");
		response.getOutputStream().write(gzip);
		
	}
	
	private byte[] gzip(byte[] data) throws IOException {
		ByteArrayOutputStream bout=new ByteArrayOutputStream();
		GZIPOutputStream gout=new GZIPOutputStream(bout);
		gout.write(data);
		gout.close();
		return bout.toByteArray();
	}

	class MyResponse extends HttpServletResponseWrapper{
		private HttpServletResponse response;
		private ByteArrayOutputStream bout=new ByteArrayOutputStream();
		private PrintWriter pw;
		public MyResponse(HttpServletResponse response){
			super(response);
			this.response=response;
		}
		@Override
		public ServletOutputStream getOutputStream() throws IOException {

			return new MyServletOutputStream(bout);
		}
		
		public byte[] getData(){
			if(pw!=null){
				pw.close();
			}
			return bout.toByteArray();
		}
		@Override
		public PrintWriter getWriter() throws IOException {
			pw=new PrintWriter(new OutputStreamWriter(bout,response.getCharacterEncoding()));
			return pw;
		}
		
		
		
	}
	
	
	class MyServletOutputStream extends ServletOutputStream{

		private ByteArrayOutputStream bout;
		public MyServletOutputStream(ByteArrayOutputStream bout){
			this.bout=bout;
		}
		@Override
		public void write(int b) throws IOException {
			// TODO Auto-generated method stub
			bout.write(b);
		}
		
	}
	
	

	public void init(FilterConfig filterConfig) throws ServletException {

	}
	
	
	public void destroy() {

	}




}