gzip压缩js和html文件java源码

gzip压缩js和html文件java源码

作者：张�F 版本：V1.0 最后更新日期：2013/4/25  http://idata.blog.51cto.com

静态文件压缩是十年前的技术，在视频、图片占据带宽主流的今天对很多网站已不再重要。但是，对于数据服务而言，静态文件压缩技术依然可以摆在显著位置值得一提，甚至可以说比十年前更加重要了。究其原因根本上是因为javascript和html5。在数据服务领域，笔者相信基于javascript+html5的数据可视化技术会成为未来的主流，这正是压缩技术的用武之地。

引入第三方jar包实现压缩是可行的，但是这是以牺牲灵活性和简单性为代价的。在技术进步竞争激烈的今天，关键技术成为黑盒就好比与人赛跑的您身上又多了一道枷锁。下面的代码已在生产环境证实可行，期待您的反馈：

web.xml

<!-- ResponseFilter must be executed as the last one of the filter chain.-->
<filter>
    <filter-name>ResponseFilter</filter-name>
    <filter-class>com.datawebservice.ResponseFilter</filter-class>
</filter>
   <filter-mapping>
        <filter-name>ResponseFilter</filter-name>
        <url-pattern>/*</url-pattern>
   </filter-mapping>

ResponseFilter.java

package com.datawebservice;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;

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

public class ResponseFilter implements Filter {
        public void init(FilterConfig filterConfig) throws ServletException {}
        public void doFilter(ServletRequest request, ServletResponse response,
                        FilterChain filterChain) throws IOException, ServletException {
                HttpServletRequest httpServletRequest = (HttpServletRequest) request;
                HttpServletResponse httpServletResponse = (HttpServletResponse) response;

                String requestURI = httpServletRequest.getRequestURI();
                if (requestURI.endsWith("html")|| requestURI.endsWith("js"))
                {
                    ResponseWrapper wrapper = new ResponseWrapper(httpServletResponse);
                    filterChain.doFilter(request, wrapper);
                    String resultText = wrapper.getResultText();
                    wrapper.close();

                    //压缩
                    ByteArrayOutputStream os = new ByteArrayOutputStream();
                    GZIPOutputStream gzip = new GZIPOutputStream(os);
                    gzip.write(resultText.getBytes("UTF-8"));
                    gzip.close();

                     //输出
                     byte[] bytes = os.toByteArray();
                     httpServletResponse.setContentType("text/html; charset=UTF-8");
                     httpServletResponse.addHeader("Content-Length",Integer.toString(bytes.length));
                     httpServletResponse.addHeader("Content-Encoding", "gzip");
                     ServletOutputStream output = httpServletResponse.getOutputStream();
                     output.write(bytes);
                     output.flush();
                     output.close();
                }else {
                    filterChain.doFilter(httpServletRequest, httpServletResponse);
                }
        }
        public void destroy() {}
}

ResponseWrapper.java

package com.datawebservice;

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

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

public class ResponseWrapper extends HttpServletResponseWrapper {
    private String responseText="";
    private ByteArrayOutputStream responseStream=null;

    public ResponseWrapper(HttpServletResponse response) {
        super(response);
        responseStream = new ByteArrayOutputStream();
    }

    public String getResultText() {
        if(responseText.equals("")){
            try{
                responseText= new String(responseStream.toByteArray(),"UTF-8");
            }catch(Exception e){
                System.out.println("getResultText exception");
                System.out.println(e.getMessage());
            }
        }
        return responseText;
    }

    public byte[] getStreamBytes() {
        return responseStream.toByteArray();
    }

    public void close(){
        try{
          responseStream.close();
        }catch(Exception e){
            System.out.println("ResponseWrapper.responseStream.close() throw exception");
            System.out.println(e.getMessage());
        }
    }

    public ServletOutputStream getOutputStream() throws IOException {
        return (new MyServletOutputStream());
    }

    public PrintWriter getWriter() throws IOException {
        return (new MyPrintWriter(new PrintWriter(new MyServletOutputStream())));
    }

      class MyServletOutputStream extends ServletOutputStream{
          MyServletOutputStream(){
          }
          public void close() throws IOException {
              super.close();
          }
          public void flush() throws IOException {
                super.flush();
          }
          public void write(int b) throws IOException {
                write((byte)b);
          }
          public void write(byte b[]) throws IOException {
              write(b, 0, b.length);
          }
          public void write(byte b[], int off, int len) throws IOException {
             responseStream.write(b, off, len);
          }//end write
      }//end class MyServletOutputStream

      class MyPrintWriter extends PrintWriter{
          MyPrintWriter(Writer out){
              super(out);
          }
          public void flush(){
          }
          public void close(){
          }
          public void write(int b) {
              char[] cb = new char[1];
              cb[0]=(char)b;
              write(cb);
          }
          public void write(char[] chars) {
              write(chars,0,chars.length);
          }
          public void write(String s){
              responseText=responseText+s;
          }
          public void write(char buf[],int off,int len){
              responseText=responseText+String.copyValueOf(buf, off, len);
          }
          public void write(String s,int off,int len){
              responseText=responseText+s.substring(off, off+len);
          }
      }
}

补充说明：我使用了内部类来简化代码。如果您不乏冒险精神，这份代码也可用于压缩jsp。