HttpClient使用管道流提交Multipart请求

HttpClient 是JDK11提供的一个全新HTTP客户端Api，超级好用。

Multipart 请求

HttpClient 并没有提供 Multipart 请求体的构建Api。但是可以使用apache的开源httpmime库来进行构建。

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpmime -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpmime</artifactId>
    <version>4.5.13</version>
</dependency>

构建一个 MultipartBody

// 构建Multipart请求
HttpEntity httpEntity = MultipartEntityBuilder.create()
        // 表单数据
        .addPart("name", new StringBody(UriUtils.encode("SpringBoot中文社区", StandardCharsets.UTF_8), ContentType.APPLICATION_FORM_URLENCODED))
        // JSON数据
        .addPart("info", new StringBody("{\"site\": \"https://springboot.io\", \"now\": 2021}", ContentType.APPLICATION_JSON))
        // 文件数据
        .addBinaryBody("file", file, ContentType.APPLICATION_OCTET_STREAM, "eclipse-jee-2019-12-R-win32-x86_64.zip")
        .build();

ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream((int) httpEntity.getContentLength());

// 把body写入到内存
httpEntity.writeTo(byteArrayOutputStream);

Multipart 请求可以一次性post多个子body，通常用来上传本地磁盘上的文件。所以这种请求体可能会异常庞大。甚至内存不能完整的存入整个请求体。那么这个时候有2种办法可以解决。

1. 先把构建好的Body数据写入到磁盘，再通过IO磁盘数据，提交给服务器
2. 使用管道流，在读取磁盘数据进行body构建的时候，直接通过管道提交到远程服务器

管道流

管道流，顾名思义，可以往一边写，从另一边读。

// 创建读取流
PipedInputStream pipedInputStream = new PipedInputStream();
// 创建写入流
PipedOutputStream pipedOutputStream = new PipedOutputStream();
// 连接写入和读取流
pipedInputStream.connect(pipedOutputStream);

通过往pipedOutputStream写入数据，就可以在pipedInputStream 读取。

不能使用单线程既读又写，因为读写都是阻塞方法。任何一方阻塞住了了，另一方就会一直处于等待状态，导致死锁

完整Demo

客户端

package io.springcloud.test;

import java.io.IOException;
import java.io.InputStream;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpResponse;
import java.net.http.HttpResponse.BodyHandlers;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

import org.apache.http.HttpEntity;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.StringBody;
import org.springframework.web.util.UriUtils;

public class MainTest {


    public static void main(String[] args) throws Exception {
        
        // 管道流
        PipedInputStream pipedInputStream = new PipedInputStream();
        PipedOutputStream pipedOutputStream = new PipedOutputStream();
        pipedInputStream.connect(pipedOutputStream);
        
        // 本地文件
        InputStream file =  Files.newInputStream(Paths.get("D:\\eclipse-jee-2019-12-R-win32-x86_64.zip"));
        
        // 构建Multipart请求
        HttpEntity httpEntity = MultipartEntityBuilder.create()
                // 表单数据
                .addPart("name", new StringBody(UriUtils.encode("SpringBoot中文社区", StandardCharsets.UTF_8), ContentType.APPLICATION_FORM_URLENCODED))
                // JSON数据
                .addPart("info", new StringBody("{\"site\": \"https://springboot.io\", \"now\": 2021}", ContentType.APPLICATION_JSON))
                // 文件数据
                .addBinaryBody("file", file, ContentType.APPLICATION_OCTET_STREAM, "eclipse-jee-2019-12-R-win32-x86_64.zip")
                .build();
        
        // 异步写入数据到管道流
        new Thread(() -> {
            try (file; pipedOutputStream){
                httpEntity.writeTo(pipedOutputStream);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }).start();
        
        HttpClient httpClient = HttpClient.newHttpClient();
        
        try (pipedInputStream){
            // 创建请求和请求体
            HttpRequest request = HttpRequest
                        .newBuilder(new URI("http://localhost/upload"))
                        // 设置ContentType
                        .header("Content-Type", httpEntity.getContentType().getValue())
                        .header("Accept", "text/plain")   
                        // 从管道流读取数据，提交给服务器
                        .POST(BodyPublishers.ofInputStream(() -> pipedInputStream))
                        .build();
            
            // 执行请求，获取响应
            HttpResponse<String> responseBody = httpClient.send(request, BodyHandlers.ofString(StandardCharsets.UTF_8));
            
            System.out.println(responseBody.body());
        }
    }
}

服务端

package io.springcloud.web.controller;

import java.nio.charset.StandardCharsets;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.util.UriUtils;

import com.google.gson.JsonObject;


@RestController
@RequestMapping("/upload")
public class UploadController {
    
    private static final Logger LOGGER = LoggerFactory.getLogger(UploadController.class);
    
    @PostMapping
    public Object upload (@RequestPart("file") MultipartFile file,
                        @RequestPart("info") JsonObject info,
                        @RequestPart("name") String name) {
        
        LOGGER.info("file: name={}, size={}", file.getOriginalFilename(), file.getSize());
        LOGGER.info("info: {}", info.toString());
        LOGGER.info("name: {}", UriUtils.decode(name, StandardCharsets.UTF_8));
        
        return ResponseEntity.ok("success");
    }
}

启动服务端后，执行客户端请求，服务端日志输出

2021-09-24 13:38:15.067  INFO 2660 --- [  XNIO-1 task-1] i.s.web.controller.UploadController      : file: name=eclipse-jee-2019-12-R-win32-x86_64.zip, size=369653147
2021-09-24 13:38:15.067  INFO 2660 --- [  XNIO-1 task-1] i.s.web.controller.UploadController      : info: {"site":"https://springboot.io","now":2021}
2021-09-24 13:38:15.067  INFO 2660 --- [  XNIO-1 task-1] i.s.web.controller.UploadController      : name: SpringBoot中文社区

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