动态代理练习2-全站压缩流输出[response动态代理]

全站压缩流输出[response动态代理]

 

1、普通类-代理类

import java.io.ByteArrayOutputStream;
import java.io.IOException;
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;

public class GzipFilter implements Filter {

    public void init(FilterConfig arg0) throws ServletException {
    }
    public void destroy() {
    }
    public void doFilter(ServletRequest req , ServletResponse res,FilterChain chain) throws IOException, ServletException {
        
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        MyResponse myResponse = new MyResponse(response);
        chain.doFilter(request, myResponse.getProxy());
//        取得缓存中的数据
        byte[] buf = myResponse.getBuffer();
        System.out.println("压缩前：" + buf.length);
        //以下是压缩代码
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        GZIPOutputStream gout = new GZIPOutputStream(bout);
        gout.write(buf);
        gout.flush();
        gout.close();
//        取得压缩后的数据
        buf = bout.toByteArray();
        System.out.println("压缩后：" + buf.length);
//        向浏览器发送压缩后的数据
        response.setHeader("content-encoding", "gzip");
        response.setHeader("content-length", buf.length+"");
        response.getOutputStream().write(buf);
    }
}
//    1、一个普通类不实现任何接口-代理类
class MyResponse{
//    缓存
    private ByteArrayOutputStream bout = new ByteArrayOutputStream();
    //取得缓存中的数据
    public byte[] getBuffer(){
        return bout.toByteArray();
    }
//    2、代理对象的引用
    private HttpServletResponse response;
//    3、通过构造器初始化代理对象
    public MyResponse(HttpServletResponse response){
        this.response = response;
    }
//    4、写一个普通方法，该方法的返回值是接口，该接口是目标对象的实现接口
    public HttpServletResponse getProxy(){
        
        return  (HttpServletResponse) Proxy.newProxyInstance(
                MyResponse.class.getClassLoader(),//1、由哪个类加载器加载 
                response.getClass().getInterfaces(), //2、被代理类的方法
                new InvocationHandler() {
                    
                    public Object invoke(
                            Object proxy,//1、被代理的对象 
                            Method method, //2、被代理的方法
                            Object[] args//3、被代理方法的参数
                            )throws Throwable {
                        
                        if("getOutputStream".equals(method.getName())){
                            return new MyServletOutputStream(bout);
                        }
                        return null;
                    }
                });
    }
}
//    带有缓存功能的ServletOutputStream
class MyServletOutputStream extends ServletOutputStream{

    private ByteArrayOutputStream bout;
    public MyServletOutputStream(ByteArrayOutputStream bout) {
        this.bout = bout;
    }
    @Override
    public void write(int b) throws IOException {
    }
    //将字节数据写入缓存
    public void write(byte[] buf) throws IOException{
        bout.write(buf);
        bout.flush();
    }
}

2、Servlet

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ShowServlet extends HttpServlet {

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

        ServletOutputStream sout =  response.getOutputStream();
        sout.write("QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ".getBytes());
    }
}

 3、web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <filter>
        <filter-name>MyGzipFilte</filter-name>
        <filter-class>cn.zengfanshegn.proxy.servlet.GzipFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>MyGzipFilte</filter-name>
        <servlet-name>ShowServlet</servlet-name>
    </filter-mapping>

 　　<servlet>
   　　 <servlet-name>ShowServlet</servlet-name>
   　　 <servlet-class>cn.zengfanshegn.proxy.servlet.ShowServlet</servlet-class>
 　　 </servlet>
　　<servlet-mapping>
    　　<servlet-name>ShowServlet</servlet-name>
    　　<url-pattern>/ShowServlet</url-pattern>
  　</servlet-mapping>
</web-app>