简介
项目中，请求时发送超大 json 数据外；响应时也有可能返回超大 json数据。上一篇实现了请求数据的 gzip 压缩。本篇通过 filter 实现对响应 json 数据的压缩。
先了解一下以下两个概念：
- 请求头：
Accept-Encoding : gzip告诉服务器，该浏览器支持 gzip 压缩 - 响应头：
Content-Encoding : gzip告诉浏览器，输出信息使用了 gzip 进行压缩
pom.xml 引入依赖
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.olive</groupId> <artifactId>response-compression</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>response-compression</name> <url>http://maven.apache.org</url> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.5.14</version> <relativePath /> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>8</maven.compiler.source> <maven.compiler.target>8</maven.compiler.target> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>com.alibaba.fastjson2</groupId> <artifactId>fastjson2</artifactId> <version>2.0.14</version> </dependency> <dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version>2.9.0</version> </dependency> </dependencies> </project>
对Response进行包装
GzipResponseWrapper 类重新定义了输出流，拦截需要输出的数据，直接缓存到 ByteArrayOutputStream 中。
package com.olive.filter; import lombok.extern.slf4j.Slf4j; import javax.servlet.ServletOutputStream; import javax.servlet.WriteListener; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpServletResponseWrapper; import java.io.*; @Slf4j public class GzipResponseWrapper extends HttpServletResponseWrapper { /** * 字节数组缓冲流，用来保存截获到的输出数据 */ private ByteArrayOutputStream buffer; /** * 重新定义servlet输出流，改变输出目的地将响应内容输出到给定的字节数组缓冲流中 */ private GzipResponseWrapper.CustomServletOutputStream servletOutputStream; /** * 同上 */ private PrintWriter writer; public GzipResponseWrapper(HttpServletResponse response) { super(response); //original HttpServletResponse object buffer = new ByteArrayOutputStream(); servletOutputStream = new GzipResponseWrapper.CustomServletOutputStream(buffer); try { writer = new PrintWriter(new OutputStreamWriter(buffer, response.getCharacterEncoding()), true); } catch (UnsupportedEncodingException e) { log.error("GZipHttpServletResponse", e); } } @Override public ServletOutputStream getOutputStream() throws IOException { return servletOutputStream; } @Override public PrintWriter getWriter() throws IOException { return writer; } @Override public void flushBuffer() throws IOException { if (servletOutputStream != null) { servletOutputStream.flush(); } if (writer != null) { writer.flush(); } } /** * 向外部提供一个获取截获数据的方法 * @return 从response输出流中截获的响应数据 */ public byte[] getOutputData() throws IOException { flushBuffer(); return buffer.toByteArray(); } private static class CustomServletOutputStream extends ServletOutputStream { /** * 字节数组缓冲流，用来保存截获到的输出数据 */ private ByteArrayOutputStream buffer; public CustomServletOutputStream(ByteArrayOutputStream buffer) { this.buffer = buffer; } @Override public boolean isReady() { return true; } @Override public void setWriteListener(WriteListener listener) { } /** * 重写输出流相关的方法 * 将输出数据写出到给定的ByteArrayOutputStream缓冲流中保存起来 * @param b 输出的数据 * @throws IOException */ @Override public void write(int b) throws IOException { buffer.write(b); } } }
定义GzipFilter对输出进行拦截
GzipFilter 拦截器获取缓存的需要输出的数据，进行压缩，在输出数据之前先设置响应头Content-Encoding : gzip。
package com.olive.filter; import lombok.extern.slf4j.Slf4j; import org.springframework.http.HttpHeaders; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.*; import java.util.zip.GZIPOutputStream; /** * 压缩过滤器 * * 功能:对于返回给客户端的数据进行gzip压缩,提高响应速度 * 实现说明: * 要对response对象的输出数据进行gzip压缩,首先得拿到后面servlet(controller)进行业务处理后往response对象里写入的数据 * 可以通过重写response对象,修改该对象内部的输出流,使该流写出数据时写出到给定的字节数组缓冲流当中, * 并在重写后的response对象内部提供一个获取该字节数组缓冲流的方法,这样就可以截获响应数据 * 然后就可以对截获的响应数据通过Gzip输出流进行压缩输出即可; * 因为响应数据是gzip压缩格式,不是普通的文本格式所以需要通过response对象(响应头)告知浏览器响应的数据类型 */ @Slf4j public class GzipFilter implements Filter { private final String GZIP = "gzip"; public void destroy() { log.info("GzipFilter destroy"); } public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { log.info("GzipFilter start"); HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) resp; String acceptEncoding = request.getHeader(HttpHeaders.ACCEPT_ENCODING); //searching for 'gzip' in ACCEPT_ENCODING header if( acceptEncoding != null && acceptEncoding.indexOf(GZIP) >= 0){ GzipResponseWrapper gzipResponseWrapper = new GzipResponseWrapper(response); //pass the customized response object to controller to capture the output data chain.doFilter(request, gzipResponseWrapper); //get captured data byte[] data = gzipResponseWrapper.getOutputData(); log.info("截获到数据：" + data.length + " bytes"); //get gzip data ByteArrayOutputStream gzipBuffer = new ByteArrayOutputStream(); GZIPOutputStream gzipOut = new GZIPOutputStream(gzipBuffer); gzipOut.write(data); gzipOut.flush(); gzipOut.close(); byte[] gzipData = gzipBuffer.toByteArray(); log.info("压缩后数据：" + gzipData.length + " bytes"); //set response header and output response.setHeader(HttpHeaders.CONTENT_ENCODING, GZIP); response.getOutputStream().write(gzipData); response.getOutputStream().flush(); }else{ chain.doFilter(req, resp); } } public void init(FilterConfig config) throws ServletException { log.info("GzipFilter init"); } }
注册 GzipFilter 拦截器
package com.olive.config; import com.olive.filter.GzipFilter; import org.springframework.boot.web.servlet.FilterRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; /** * 注册filter */ @Configuration public class FilterRegistration { @Bean public FilterRegistrationBean<GzipFilter> gzipFilterRegistrationBean() { FilterRegistrationBean<GzipFilter> registration = new FilterRegistrationBean<>(); //Filter可以new，也可以使用依赖注入Bean registration.setFilter(new GzipFilter()); //过滤器名称 registration.setName("gzipFilter"); //拦截路径 registration.addUrlPatterns("/*"); //设置顺序 registration.setOrder(1); return registration; } }
定义 Controller
该 Controller 非常简单，主要读取一个大文本文件，作为输出的内容。
package com.olive.controller; import java.io.File; import java.util.HashMap; import java.util.Map; import com.olive.vo.ArticleRequestVO; import org.apache.commons.io.FileUtils; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class TestController { @RequestMapping("/getArticle") public Map<String, Object> getArticle(){ Map<String, Object> result = new HashMap<>(); result.put("code", 200); result.put("msg", "success"); byte[] bytes = null; try { bytes = FileUtils.readFileToByteArray(new File("C:\\Users\\2230\\Desktop\\凯平项目资料\\改装车项目\\CXSSBOOT_DB_DDL-1.0.9.sql")); }catch (Exception e){ } String content = new String(bytes); ArticleRequestVO vo = new ArticleRequestVO(); vo.setId(1L); vo.setTitle("BUG弄潮儿"); vo.setContent(content); result.put("body", vo); return result; } }
Controller 返回数据的 VO
package com.olive.vo; import lombok.Data; import java.io.Serializable; @Data public class ArticleRequestVO implements Serializable { private Long id; private String title; private String content; }
定义 Springboot 引导类
package com.olive; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class); } }
测试
测试的curl
curl -X POST http://127.0.0.1:8080/getArticle
