使用动态代理进行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.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
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;


//采用动态代理进行Gzip过滤
public class GzipFilterProxy implements Filter {

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

	}

	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		HttpServletRequest request = (HttpServletRequest) req;
		final HttpServletResponse response = (HttpServletResponse) res;
		final ByteArrayOutputStream bout = new ByteArrayOutputStream();
		final PrintWriter pw = new PrintWriter(new OutputStreamWriter(bout,
				response.getCharacterEncoding()));

		chain.doFilter(request, (ServletResponse) Proxy.newProxyInstance(this
				.getClass().getClassLoader(), response.getClass()
				.getInterfaces(), new InvocationHandler() {

			@Override
			public Object invoke(Object proxy, Method method, Object[] args)
					throws Throwable {
				String methodname = method.getName();
				if (methodname.equals("getOutputStream")) {//如果调用getOutputStream()方法，则返回保存了数据的字节数据流
					return new MyServletOutputStream(bout);
				} else if (methodname.equals("getWriter")) {//如果调用getWriter()方法，则返回保存了数据的PrintWriter流
					return pw;
				} else {
					return method.invoke(response, args);
				}

			}

		}));
		//Pintwriter 存在缓冲，调用之前进行缓存清空，字节缓冲才能才能得到数据
		if (pw != null) {
			pw.close();
		}
		byte data[] = bout.toByteArray();
		System.out.println("原始大小：" + data.length);

		byte[] gzip = gzip(data);
		//告诉浏览器获得的数据是压缩后的数据
		response.setHeader("content-encoding", "gzip");
		response.setHeader("content-length", gzip.length + "");
		response.getOutputStream().write(gzip);

	}
	//进行数据压缩
	private byte[] gzip(byte[] data) throws IOException {
		ByteArrayOutputStream bout = new ByteArrayOutputStream();
		GZIPOutputStream gout = new GZIPOutputStream(bout);
		gout.write(data);
		gout.close();
		return bout.toByteArray();
	}
	//创建ServletOutputStream子类，覆盖write方法，从而使数据写到字节数组中
	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 {
		// TODO Auto-generated method stub

	}

}