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缓存过滤器

时间:2016-07-23 21:34:34      阅读:140      评论:0      收藏:0      [点我收藏+]

标签:缓存过滤器


                          缓存过滤器


import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.OutputStreamWriter;

import java.io.PrintWriter;

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.ServletOutputStream;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpServletResponseWrapper;


/**

 * Servlet Filter implementation class CacheFilter

 */

public class CacheFilter implements Filter {

    private Map<String,byte[]> map = new HashMap();//缓存

    /**

     * Default constructor. 

     */

    public CacheFilter() {

        // TODO Auto-generated constructor stub

    }


/**

* @see Filter#destroy()

*/

public void destroy() {

// TODO Auto-generated method stub

}


/**

* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)

*/

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

HttpServletRequest request = (HttpServletRequest) req;

HttpServletResponse response = (HttpServletResponse) res;


// TODO Auto-generated method stub

// place your code here

        //1.得到用户请求的url

String uri = request.getRequestURI();

//2.看缓存中有没有url对应的数据

byte data[] = map.get(uri);

//3.如果缓存中有数据,直接返回

if(data != null){

response.getOutputStream().write(data);

return;

}

//4.如果没有,让目标资源执行,并捕获目标资源输出

BufferHttpResponse bufferHttpResponse = new BufferHttpResponse(response);

chain.doFilter(request, response);

byte out[] = bufferHttpResponse.getBuffer();

//5.把目标资源数据以uri为关键字保存到缓存中

map.put(uri, out);

//6.把数据输出到浏览器

response.getOutputStream().write(out);

}


/**

* @see Filter#init(FilterConfig)

*/

public void init(FilterConfig fConfig) throws ServletException {

// TODO Auto-generated method stub

}

}



class BufferHttpResponse extends HttpServletResponseWrapper {

private HttpServletResponse response;

private ByteArrayOutputStream bout = new ByteArrayOutputStream();

private PrintWriter pw;


public BufferHttpResponse(HttpServletResponse response) {

super(response);

this.response = response;

}


@Override

public ServletOutputStream getOutputStream() throws IOException {

return new MyServletOutputStream(bout);

}


@Override

public PrintWriter getWriter() throws IOException {

pw = new PrintWriter(new OutputStreamWriter(bout,this.response.getCharacterEncoding()));

return pw;

}


public byte[] getBuffer() {

try {

            if(pw != null){

            pw.close();

            }

if (bout != null)

bout.flush();

return bout.toByteArray();

} catch (Exception e) {

throw new RuntimeException(e);

}

}


}


class MyServletOutputStream extends ServletOutputStream {

private ByteArrayOutputStream bout;


public MyServletOutputStream(ByteArrayOutputStream bout) {

this.bout = bout;

}


@Override

public void write(int arg0) throws IOException {


}


}


本文出自 “德泽无忧” 博客,谢绝转载!

缓存过滤器

标签:缓存过滤器

原文地址:http://dezewuyou.blog.51cto.com/2628602/1829014

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