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HTTP gzip压缩

gzip压缩

一. HTTP gzip压缩,概述

  • request
    • header中声明Accept-Encoding : gzip，告知服务器客户端接受gzip的数据
  • response
    • body，同时加入以下header：Content-Encoding: gzip：表明body是gzip过的数据
    • Content-Length:117：表示body gzip压缩后的数据大小，便于客户端使用
    • 或Transfer-Encoding: chunked：分块传输编码
二. 如何使用gzip进行压缩Tomcat开启压缩（gzip）
tomcat server.xml
<Connectorcompression="on" # 表示开启压缩noCompressionUserAgents="gozilla, traviata"compressionMinSize="2048" # 表示会对大于2KB的文件进行压缩compressableMimeType="text/html,text/xml,text/css,text/JAVAscript,image/gif,image/jpg" # 是指将进行压缩的文件类型/>
  • 弊端
    对HTTP传输内容进行压缩是改良前端响应性能的可用方法之一，大型网站都在用 。但是也有缺点，就是压缩过程占用cpu的资源，客户端浏览器解析也占据了一部分时间 。但是随着硬件性能不断的提高，这些问题正在不断的弱化 。
程序压缩/解压
GZIPInputStream(解压) / GZIPOutputStream(压缩)
  • netflix.zuul相关示例
【HTTP gzip压缩】# org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter#writeResponse()is = context.getResponseDataStream();InputStream inputStream = is;if (is != null) {if (context.sendZuulResponse()) {// if origin response is gzipped, and client has not requested gzip,// decompress stream// before sending to client// else, stream gzip directly to clientif (context.getResponseGZipped() && !isGzipRequested) {// If origin tell it's GZipped but the content is ZERO bytes,// don't try to uncompressfinal Long len = context.getOriginContentLength();if (len == null || len > 0) {try {inputStream = new GZIPInputStream(is);}catch (java.util.zip.ZipException ex) {log.debug("gzip expected but not "+ "received assuming unencoded response "+ RequestContext.getCurrentContext().getRequest().getRequestURL().toString());inputStream = is;}}else {// Already done : inputStream = is;}}else if (context.getResponseGZipped() && isGzipRequested) {servletResponse.setHeader(ZuulHeaders.CONTENT_ENCODING, "gzip");}writeResponse(inputStream, outStream);}}# com.netflix.zuul.http.HttpServletRequestWrApper.UnitTest#handlesGzipRequestBody@Testpublic void handlesGzipRequestBody() throws IOException {// creates string, gzips into byte array which will be mocked as InputStream of requestfinal String body = "hello";final byte[] bodyBytes = body.getBytes();// in this case the compressed stream is actually larger - need to allocate enough spacefinal ByteArrayOutputStream byteOutStream = new ByteArrayOutputStream(0);final GZIPOutputStream gzipOutStream = new GZIPOutputStream(byteOutStream);gzipOutStream.write(bodyBytes);gzipOutStream.finish();gzipOutStream.flush();body(byteOutStream.toByteArray());final HttpServletRequestWrapper wrapper = new HttpServletRequestWrapper(request);assertEquals(body, IOUtils.toString(new GZIPInputStream(wrapper.getInputStream())));}示例: 网关主动对response进行压缩响应(可减少带宽) GZIPOutputStream
  • 简单实现示例.实际情况需考虑更新情况,如是否已经被压缩等
InputStream inputStream = okResponse.body().byteStream();try {// 网关主动对response进行压缩响应(可减少带宽)HttpServletRequest request = RequestContext.getCurrentContext().getRequest();boolean isGatewayGZIP = Boolean.parseBoolean(request.getHeader("x-gateway-gzip"));if (!isGatewayGZIP) {isGatewayGZIP = Boolean.parseBoolean(request.getParameter("x-gateway-gzip"));}if (isGatewayGZIP) {final ByteArrayOutputStream byteOutStream = new ByteArrayOutputStream(0);final GZIPOutputStream gzipOutStream = new GZIPOutputStream(byteOutStream);gzipOutStream.write(okResponse.body().bytes());gzipOutStream.finish();gzipOutStream.flush();inputStream = new ServletInputStreamWrapper(byteOutStream.toByteArray());httpHeaders.add(ZuulHeaders.CONTENT_ENCODING, "gzip");}} catch (Exception e) {logger.error("GatewayGZIP error:", e);}三.okhttp 压缩相关处理okHttp 解压gzip,条件: Content-Encoding = gizp
  • okio.GzipSource
if (transparentGzip&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))&& HttpHeaders.hasBody(networkResponse)) { GzipSource responseBody = new GzipSource(networkResponse.body().source()); Headers strippedHeaders = networkResponse.headers().newBuilder().removeAll("Content-Encoding").removeAll("Content-Length").build(); responseBuilder.headers(strippedHeaders); String contentType = networkResponse.header("Content-Type"); responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));}


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