GZIP压缩提高网络传输效率

【spring】通过GZIP压缩提高网络传输效率（可以实现任何资源的gzip压缩、包括AJAX）

gzip是http协议中使用的一种加密算法,客户端向web服务器端发出了请求后，通常情况下服务器端会将页面文件和其他资源，返回到客户端，客户端加载后渲染呈现，这种情况文件一般都比较大，如果开启Gzip ，那么服务器端响应后，会将页面，JS,CSS等文本文件或者其他文件通过高压缩算法将其压缩，然后传输到客户端，由客户端的浏览器负责解压缩与呈现。通常能节省40%以上的流量（一般都有60%左右），一些PHP，JSP文件也能够进行压缩。

1、通过WEB服务器打开GZIP压缩服务

      目前大多数主流WEB中间件都支持GZIP压缩、下面以Tomcat 为例进行说明：

      找到Tomcat 目录下的conf下的server.xml，并找到如下信息

      <Connector port = "8080" maxHttpHeaderSize = "8192" maxThreads = "150" minSpareThreads = "25"

              maxSpareThreads = "75" enableLookups = "false" redirectPort = "8443" acceptCount = "100"

              connectionTimeout = "20000" disableUploadTimeout = "true"

      将它改成如下的形式（其实在上面代码的下面已经有了，将他们打开而已。）：

      <Connector port="8080" maxHttpHeaderSize="8192" maxThreads="150" minSpareThreads="25"

             maxSpareThreads="75" enableLookups="false" redirectPort="8443" acceptCount="100"

             connectionTimeout="20000" disableUploadTimeout="true"

             compression="on" compressionMinSize="2048" noCompressionUserAgents="gozilla, traviata"

             compressableMimeType="text/html,text/xml" >

      这样，就能够对html和xml进行压缩了，如果要压缩css 和 js，那么需要将

           compressableMimeType=”text/html,text/xml”加入css和js：

           <Connector port="8080" ......... compressableMimeType="text/html,text/xml,text/css,text/javascript" >

      一般文本类型的静态文件可以通过这种方式压缩后传输、提高传输效率。

      已压缩过的静态文件（如图片）进行gzip压缩后大小基本无变化、所以一般不进行压缩。

2、通过过滤器实现gzip压缩

package com.tyyd.framework.web;

import java.io.IOException;

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 org.apache.commons.io.FilenameUtils;
import org.apache.commons.lang.StringUtils;

import com.tyyd.framework.core.AcwsInfo;
import com.tyyd.framework.core.AcwsMonitorLog;
import com.tyyd.framework.core.BufferedResponse;
import com.tyyd.framework.core.util.ZipUtil;

/**
 * HTTP访问过滤器
 */
public class PageVisitFilter2 implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        //性能监控
        long startTime = System.currentTimeMillis();

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

        String uri = request.getRequestURI();
        String ext = FilenameUtils.getExtension(uri);

        try{
            response.setHeader("Pragma", "No-cache");
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expires", -1);
            request.setCharacterEncoding("UTF-8");
            response.setCharacterEncoding("UTF-8");

            response.setHeader("renderer", "webkit");
            response.setHeader("viewport", "width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0 user-scalable=no");

            if(isGZipEncoding(request)){
                //需要过滤的扩展名：.htm,.html,.jsp,.js,.ajax,.css
                String gzippPattern=",.htm,.html,.jsp,.js,.ajax,.css,";
                if(StringUtils.indexOf(gzippPattern, ",."+ext+",")!=-1){
                    BufferedResponse gzipResponse = new BufferedResponse(response);
                    chain.doFilter(request, gzipResponse);
                    byte[] srcData = gzipResponse.getResponseData();
                    byte[] outData = null;
                    if(srcData.length > 512){
                        byte[] gzipData = ZipUtil.toGzipBytes(srcData);
                        response.addHeader("Content-Encoding", "gzip");
                        response.setContentLength(gzipData.length);
                        outData = gzipData;
                    } else {
                        outData = srcData;
                    }
                    ServletOutputStream output = response.getOutputStream();
                    output.write(outData);
                    output.flush();
                } else {
                    chain.doFilter(request, response);
                }
                return;
            }

            chain.doFilter(request, response);
        }catch(Exception e){

        }finally{
            AcwsMonitorLog.warnHttpVisit(startTime, request);
        }
    }

    @Override
    public void destroy() {
    }

    /**
     * 判断浏览器是否支持GZIP
     * @param request
     * @return
     */
    private boolean isGZipEncoding(HttpServletRequest request){
      boolean flag=false;
      String encoding=request.getHeader("Accept-Encoding");
      if(encoding.indexOf("gzip")!=-1){
        flag=true;
      }
      return flag;
    }
}

package com.tyyd.framework.core;


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;

public class BufferedResponse extends HttpServletResponseWrapper {
    public static final int OT_NONE = 0, OT_WRITER = 1, OT_STREAM = 2;

    private BufferedOutputStream outputStream = null;
    private PrintWriter writer = null;
    private int outputType = OT_NONE;

    public BufferedResponse(HttpServletResponse response) {
        super(response);
        outputStream = new BufferedOutputStream();
    }

    public PrintWriter getWriter() throws IOException {
        if (outputType == OT_STREAM)
            throw new IllegalStateException();
        else if (outputType == OT_WRITER)
            return writer;
        else {
            outputType = OT_WRITER;
            writer = new PrintWriter(new OutputStreamWriter(outputStream,
                    getCharacterEncoding()), true);
            return writer;
        }
    }

    public ServletOutputStream getOutputStream() throws IOException {
        if (outputType == OT_WRITER)
            throw new IllegalStateException();
        else if (outputType == OT_STREAM)
            return outputStream;
        else {
            outputType = OT_STREAM;
            return outputStream;
        }
    }
    public void flushBuffer() throws IOException {
        try{writer.flush();}catch(Exception e){}
        try{outputStream.flush();}catch(Exception e){}
    }

    public void reset() {
        outputType = OT_NONE;
        outputStream.reset();
    }

    public byte[] getResponseData() throws IOException {
        flushBuffer();
        return outputStream.toByteArray();
    }
}

/**
 * 版权所有：
 * 项目名称:框架
 * 创建者: Wangdf
 * 创建日期: 2015-2-27
 * 文件说明: AJAX 缓存输出流
 */
package com.tyyd.framework.core;

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

import javax.servlet.ServletOutputStream;

public class BufferedOutputStream extends ServletOutputStream {
    private ByteArrayOutputStream outputStream = null;

    public BufferedOutputStream(){
        outputStream = new ByteArrayOutputStream(1024);
    }


    /**
     * Writes the specified byte to this output stream. The general
     * contract for <code>write</code> is that one byte is written
     * to the output stream. The byte to be written is the eight
     * low-order bits of the argument <code>b</code>. The 24
     * high-order bits of <code>b</code> are ignored.
     * <p>
     * Subclasses of <code>OutputStream</code> must provide an
     * implementation for this method.
     *
     * @param      b   the <code>byte</code>.
     * @exception  IOException  if an I/O error occurs. In particular,
     *             an <code>IOException</code> may be thrown if the
     *             output stream has been closed.
     */
    public void write(int b) throws IOException {
        outputStream.write(b);
    }

    /**
     * Writes <code>b.length</code> bytes from the specified byte array
     * to this output stream. The general contract for <code>write(b)</code>
     * is that it should have exactly the same effect as the call
     * <code>write(b, 0, b.length)</code>.
     *
     * @param      b   the data.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.OutputStream#write(byte[], int, int)
     */
    public void write(byte b[]) throws IOException {
        outputStream.write(b);
    }

    /**
     * Writes <code>len</code> bytes from the specified byte array
     * starting at offset <code>off</code> to this output stream.
     * The general contract for <code>write(b, off, len)</code> is that
     * some of the bytes in the array <code>b</code> are written to the
     * output stream in order; element <code>b[off]</code> is the first
     * byte written and <code>b[off+len-1]</code> is the last byte written
     * by this operation.
     * <p>
     * The <code>write</code> method of <code>OutputStream</code> calls
     * the write method of one argument on each of the bytes to be
     * written out. Subclasses are encouraged to override this method and
     * provide a more efficient implementation.
     * <p>
     * If <code>b</code> is <code>null</code>, a
     * <code>NullPointerException</code> is thrown.
     * <p>
     * If <code>off</code> is negative, or <code>len</code> is negative, or
     * <code>off+len</code> is greater than the length of the array
     * <code>b</code>, then an <tt>IndexOutOfBoundsException</tt> is thrown.
     *
     * @param      b     the data.
     * @param      off   the start offset in the data.
     * @param      len   the number of bytes to write.
     * @exception  IOException  if an I/O error occurs. In particular,
     *             an <code>IOException</code> is thrown if the output
     *             stream is closed.
     */
    public void write(byte b[], int off, int len) throws IOException {
        outputStream.write(b, off, len);
    }
    /**
     * Writes a <code>String</code> to the client,
     * without a carriage return-line feed (CRLF)
     * character at the end.
     *
     *
     * @param s         the <code>String</code> to send to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */
    public void print(String s) throws IOException {
        print(s, "UTF-8");
    }

    public void print(String s, String charsetName) throws IOException {
        /*
         * 解决中文乱码问题
         */
        outputStream.write(s.getBytes(charsetName));
    }



    /**
     * Writes a <code>boolean</code> value to the client,
     * with no carriage return-line feed (CRLF)
     * character at the end.
     *
     * @param b         the <code>boolean</code> value
     *              to send to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void print(boolean b) throws IOException {
        print(b?"true":"false");
    }



    /**
     * Writes a character to the client,
     * with no carriage return-line feed (CRLF)
     * at the end.
     *
     * @param c         the character to send to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void print(char c) throws IOException {
        print(String.valueOf(c));
    }

    /**
     *
     * Writes an int to the client,
     * with no carriage return-line feed (CRLF)
     * at the end.
     *
     * @param i         the int to send to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void print(int i) throws IOException {
        print(String.valueOf(i));
    }




    /**
     *
     * Writes a <code>long</code> value to the client,
     * with no carriage return-line feed (CRLF) at the end.
     *
     * @param l         the <code>long</code> value
     *              to send to the client
     *
     * @exception IOException   if an input or output exception
     *              occurred
     *
     */

    public void print(long l) throws IOException {
        print(String.valueOf(l));
    }



    /**
     *
     * Writes a <code>float</code> value to the client,
     * with no carriage return-line feed (CRLF) at the end.
     *
     * @param f         the <code>float</code> value
     *              to send to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     *
     */

    public void print(float f) throws IOException {
        print(String.valueOf(f));
    }



    /**
     *
     * Writes a <code>double</code> value to the client,
     * with no carriage return-line feed (CRLF) at the end.
     *
     * @param d         the <code>double</code> value
     *              to send to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void print(double d) throws IOException {
        print(String.valueOf(d));
    }



    /**
     * Writes a carriage return-line feed (CRLF)
     * to the client.
     *
     *
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void println() throws IOException {
        print("
");
    }



    /**
     * Writes a <code>String</code> to the client,
     * followed by a carriage return-line feed (CRLF).
     *
     *
     * @param s         the <code>String</code> to write to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */
    public void println(String s){
        println(s, "UTF-8");
    }
    public void println(String s, String charsetName){
        /*
         * 解决中文乱码问题
         */
        try {
            print(s,charsetName);
            println();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }




    /**
     *
     * Writes a <code>boolean</code> value to the client,
     * followed by a
     * carriage return-line feed (CRLF).
     *
     *
     * @param b         the <code>boolean</code> value
     *              to write to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void println(boolean b) throws IOException {
        print(b);
        println();
    }



    /**
     *
     * Writes a character to the client, followed by a carriage
     * return-line feed (CRLF).
     *
     * @param c         the character to write to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void println(char c) throws IOException {
        print(c);
        println();
    }



    /**
     *
     * Writes an int to the client, followed by a
     * carriage return-line feed (CRLF) character.
     *
     *
     * @param i         the int to write to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void println(int i) throws IOException {
        print(i);
        println();
    }



    /**
     *
     * Writes a <code>long</code> value to the client, followed by a
     * carriage return-line feed (CRLF).
     *
     *
     * @param l         the <code>long</code> value to write to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void println(long l) throws IOException {
        print(l);
        println();
    }



    /**
     *
     * Writes a <code>float</code> value to the client,
     * followed by a carriage return-line feed (CRLF).
     *
     * @param f         the <code>float</code> value
     *              to write to the client
     *
     *
     * @exception IOException   if an input or output exception
     *              occurred
     *
     */

    public void println(float f) throws IOException {
        print(f);
        println();
    }



    /**
     *
     * Writes a <code>double</code> value to the client,
     * followed by a carriage return-line feed (CRLF).
     *
     *
     * @param d         the <code>double</code> value
     *              to write to the client
     *
     * @exception IOException   if an input or output exception occurred
     *
     */

    public void println(double d) throws IOException {
        print(d);
        println();
    }
    /**
     * Flushes this output stream and forces any buffered output bytes
     * to be written out. The general contract of <code>flush</code> is
     * that calling it is an indication that, if any bytes previously
     * written have been buffered by the implementation of the output
     * stream, such bytes should immediately be written to their
     * intended destination.
     * <p>
     * If the intended destination of this stream is an abstraction provided by
     * the underlying operating system, for example a file, then flushing the
     * stream guarantees only that bytes previously written to the stream are
     * passed to the operating system for writing; it does not guarantee that
     * they are actually written to a physical device such as a disk drive.
     * <p>
     * The <code>flush</code> method of <code>OutputStream</code> does nothing.
     *
     * @exception  IOException  if an I/O error occurs.
     */
    public void flush() throws IOException {
        outputStream.flush();
    }

    /**
     * Closes this output stream and releases any system resources
     * associated with this stream. The general contract of <code>close</code>
     * is that it closes the output stream. A closed stream cannot perform
     * output operations and cannot be reopened.
     * <p>
     * The <code>close</code> method of <code>OutputStream</code> does nothing.
     *
     * @exception  IOException  if an I/O error occurs.
     */
    public void close() throws IOException {
        outputStream.close();
    }

    /**
     * Resets the <code>count</code> field of this byte array output
     * stream to zero, so that all currently accumulated output in the
     * output stream is discarded. The output stream can be used again,
     * reusing the already allocated buffer space.
     *
     * @see     java.io.ByteArrayInputStream#count
     */
    public void reset() {
        outputStream.reset();
    }

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

在web.xml中配置 PageVisitFilter,当我们访问应用中以.htm,.html,.jsp,.js,.ajax,.css结尾的资源的使用,服务器端就开启http gzip压缩,将压缩后的信息通过http 协议传递给浏览器. 

<filter>
  <filter-name>Page Visit Filter</filter-name>
  <filter-class>com.tyyd.framework.web.PageVisitFilter</filter-class>
 </filter>

 <filter-mapping>
  <filter-name>Page Visit Filter</filter-name>
  <url-pattern>/*</url-pattern>
 </filter-mapping>

3、AJAX也可以通过这种方式压缩

只需知道ajax请求的后缀添加到下面的代码中即可：

//需要过滤的扩展名：.htm,.html,.jsp,.js,.ajax,.css

String gzippPattern=",.htm,.html,.jsp,.js,.ajax,.css,";