标签：实用案例－缓存数据到内存

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.itcast.web.decorator.MyResponse;

//单例
public class CacheFilter implements Filter {

    //实例变量[每个线程共享]
    private Map<String,byte[]> cache = new HashMap<String,byte[]>(); 

    public void destroy() {
    }
    public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;

        //NO1：取得客户端访问的资源路径
        String uri = request.getRequestURI();

        //NO2：根据uri去缓存中查询对应的页面资源有没有
        byte[] data = cache.get(uri);

        //NO3：如果没有
        if(data==null){

            //将请求和响应放行到web资源中   
            MyResponse myResponse = new MyResponse(response);
            chain.doFilter(request,myResponse);

            //NO4:将刚取得的数据放入到缓存中，便于下次重用
            data = myResponse.getBuffer();
            cache.put(uri,data);

            System.out.println("从服务端取得资源");

        //NO5：如果有，直接从缓存中了得数据
        }

        //NO6：向浏览器输出数据
        response.getOutputStream().write(data);
    }
    public void init(FilterConfig filterConfig) throws ServletException {
    }
}

压缩资源：

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 ShowServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        PrintWriter pw = response.getWriter();

        ServletOutputStream sout = response.getOutputStream();
        sout.write(data.getBytes("UTF-8"));
        MyServletOutputStream mySout = myResponse.getOutputStream();
    sout.write("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA".getBytes());
        //mySout.write("AAAAAA".getBytes[]);
    }
}

MyResponse

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

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

//对response对象的装饰/包装
public class MyResponse extends HttpServletResponseWrapper{
    private HttpServletResponse response;
    //缓存
    private ByteArrayOutputStream bout = new ByteArrayOutputStream();
    private PrintWriter pw;
    public MyResponse(HttpServletResponse response) {
        super(response);
        this.response = response;
    }
    //重写父类方法,目的是将字节输出到缓存中去[字节]
    public ServletOutputStream getOutputStream() throws IOException {
        return new MyServletOutputStream(bout);
    }
    //重写父类方法,目的是将字符输出到缓存中去[字符]
    public PrintWriter getWriter() throws IOException {
        pw = new PrintWriter(new OutputStreamWriter(bout,"UTF-8"));
        return pw;
    }
    //取得缓存中的数据
    public byte[] getBuffer(){
        if(pw!=null){
            pw.flush();
        }
        return bout.toByteArray();
    }
}
//带有缓存功能ServletOutputStream
class MyServletOutputStream extends ServletOutputStream{
    private ByteArrayOutputStream bout;
    public MyServletOutputStream(ByteArrayOutputStream bout) {
        this.bout = bout;
    }
    public void write(int b) throws IOException {
    }
    public void write(byte[] bytes) throws IOException {
        //将字节数组的内容写入缓存
        bout.write(bytes);
        //确保所有字节数组内容进入缓存
        bout.flush();
    }
}

Filter-缓存数据到内存：学习笔记

标签：实用案例－缓存数据到内存

原文地址：http://blog.51cto.com/357712148/2105523