通过GZIP优化性能

3/8/2017来源:ASP.NET技巧人气:1450

              原创文章,转载请注明

              gzip为一种压缩技术,在网络http传输中得到应用。gzip需要web容器,浏览器的支持。

              看一下效果

              压缩前:

              

              压缩后:

 

             这里的时间不需要纠结,开发环境在本机,这里的性能损耗主要在cpu上,也就是压缩时消耗的cpu,而且本机还跑了其他东西,不同时刻的环境不太一样。

      1、tomcat配置

               tomcat中使用gzip需要进行配置,在server.xml中,在Connector标签中加入如下属性

              

comPRession="on"
compressionMinSize="2048"
noCompressionUserAgents="gozilla,traviata"
compressableMimeType="text/html,text/CSS.text/javascript"
               compression:指定是否开启压缩

               compressionMinSize:表示小于该值进行压缩,单位为Byte

               noCompressionUserAgents:表示不进行压缩的浏览器

               compressableMimeType:表示哪些格式的文件需要被压缩

               注意:图片不要进行压缩,因为图片完全可以在项目开发中使用压缩后的图片。这样避免了压缩对于CPU的消耗

      2、代码

              除了进行tomcat配置之外,还需要对请求写一个filter进行压缩。

        2.1、GZIPOutputStream

             主要是通过该类进行压缩,它由java.util.zip包提供

        2.2、ServletResponse、HttpServletResponse、ServletResponseWrapper、HttpServletResponseWrapper、WrappedOutputStream

              需要继承HttpServletResponseWrapper,复写其中的getWriter,getOutputStream方法从而获得响应数据,然后就可以调用gzipOutputStream进行压缩。

              这里顺道说一下这几个类的关系

               ServletResponse为最基本的接口,表示response。

               HttpServletResponse扩展了ServletRespones,表示http协议下的response

               ServletResponseWrapper实现了ServletResponse

               HttpServletResponseWrapper实现了HttpServletResponse

               所以我们平时用的HttpServletResponse默认的实现为HttpServletResponseWrapper,struts2似乎在这之上又包装了一层。

               WrappedOutputStream:在我们调用getOutputStream方法时,会通过该接口的write方法输出byte

        2.3思路

              思路很清晰了,通过继承HttpServletResponseWrapper重写getWriter,getOutputStream获得响应数据,在stream的输出时,需要通过WrappedOutputStream的write方法输出byte。最后把输出的byte通过gzipOutputStream进行压缩

              来看一个实现代码

package com.zs.vehicle.filter;

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

import com.zs.vehicle.utils.Wrapper;

public class GZipFilter implements Filter{

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		HttpServletResponse resp=(HttpServletResponse) response;
		HttpServletRequest req=(HttpServletRequest) request;
		if(isGZipEncoding(req)){
			Wrapper wrapper=new Wrapper(resp);
			chain.doFilter(request, wrapper);
			byte[] gzipData=gzip(wrapper.getResponseData());
			resp.addHeader("Content-Encoding", "gzip");
			resp.setContentLength(gzipData.length);
			ServletOutputStream output=response.getOutputStream();
			output.write(gzipData);
			output.flush();
		}else{
			chain.doFilter(request, response);
		}
	}

	@Override
	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub
	}

	private static boolean isGZipEncoding(HttpServletRequest request){
		boolean flag=false;
		String encoding=request.getHeader("Accept-Encoding");
		if(encoding.indexOf("gzip")!=-1){
			flag=true;
		}
		return flag;
	}
	
	private byte[] gzip(byte[] data){
		ByteArrayOutputStream byteOutput=new ByteArrayOutputStream(10240);
		GZIPOutputStream output=null;
		try{
			output=new GZIPOutputStream(byteOutput);
			output.write(data);
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			try{
				output.close();
			}catch(Exception e){
				e.printStackTrace();
			}
		}
		return byteOutput.toByteArray();
	}
	
}

package com.zs.vehicle.utils;

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

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

public class Wrapper extends HttpServletResponseWrapper{
	
	public static final int OT_NONE=0;
	public static final int OT_WRITER=1;
	public static final int OT_STREAM=2;
	private int outputType=OT_NONE;
	private ServletOutputStream output=null;
	private PrintWriter writer=null;
	private ByteArrayOutputStream buffer=null;

	public Wrapper(HttpServletResponse response) {
		super(response);
		buffer=new ByteArrayOutputStream();
	}

	@Override
	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(buffer,getCharacterEncoding()));
			return writer;
		}
	}
	
	@Override
	public ServletOutputStream getOutputStream() throws IOException{
		if(outputType==OT_WRITER)
			throw new IllegalStateException();
		else if(outputType==OT_STREAM)
			return output;
		else{
			outputType=OT_STREAM;
			output=new WrappedOutputStream(buffer);
			return output;
		}
	}
	
	@Override
	public void flushBuffer() throws IOException{
		if(outputType==OT_WRITER)
			writer.flush();
		if(outputType==OT_STREAM)
			output.flush();
	}
	
	@Override
	public void reset(){
		outputType=OT_NONE;
		buffer.reset();
	}
	
	public byte[] getResponseData() throws IOException{
		flushBuffer();
		return buffer.toByteArray();
	}
	
	class WrappedOutputStream extends ServletOutputStream{

		private ByteArrayOutputStream buffer;
		
		public WrappedOutputStream(ByteArrayOutputStream buffer){
			this.buffer=buffer;
		}
		
		@Override
		public void write(int b) throws IOException {
			buffer.write(b);
		}
		
		public byte[] toByteArray(){
			return buffer.toByteArray();
		}

		@Override
		public boolean isReady() {
			// TODO Auto-generated method stub
			return true;
		}

		@Override
		public void setWriteListener(WriteListener listener) {
			// TODO Auto-generated method stub
			
		}
		
	}
	
}

      3、spring-boot

              对于spring-boot来说,由于其内嵌了web容器,那么它的行为是怎样的呢。

              spring-boot的web容器是默认开启了gzip压缩的,而且不会对图片进行压缩。