Springboot 中的 Filter 实现超大响应 JSON 数据压缩的方法

2022-11-13 18:11:13 响应方法数据压缩

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 {
 
    
    private ByteArrayOutputStream buffer;
 
    
    private GzipResponseWrapper.CustomServletOutputStream servletOutputStream;
 
    
    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();
        }
    }
 
    
    public byte[] getOutputData() throws IOException {
        flushBuffer();
        return buffer.toByteArray();
    }
 
    private static class CustomServletOutputStream extends ServletOutputStream {
 
        
        private ByteArrayOutputStream buffer;
 
        public CustomServletOutputStream(ByteArrayOutputStream buffer) {
            this.buffer = buffer;
        }
 
        @Override
        public boolean isReady() {
            return true;
        }
 
        @Override
        public void setWriteListener(WriteListener listener) {
        }
 
        
        @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;
 

@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;
 

@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

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