Java通过http请求发送文件MultipartFile

写了一个工具类实现Java通过http请求发送文件，但其中遇到一些坑在这里标注一下

标注1

这里设置header的时候不能给header里的Content-Length赋值，否则会报错

Caused by: java.io.IOException: UT000036: Connection terminated parsing multipart data

标注2

此处的fileNameKey对应接收方controller处的@RequestParam(value = "file")里的名字，例如这里fileNameKey需要为file，否则接收方会报错
接收方controller示例：

@RequestMapping(value = "/upload")
public R upload(@RequestParam(value = "file") MultipartFile file) {
   // xxx逻辑
}

工具类demo

import org.apache.http.Consts;
import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.util.Map;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class HttpFileUtil {

    /**
     * 以post方式调用第三方接口,以form-data 形式  发送 MultipartFile 文件数据
     *
     * @param url  post请求url
     * @param multipartFile  文件
     * @param paramMap 表单里其他参数
     * @return
     */
    public static String doPostFormData(String url, MultipartFile multipartFile, Map paramMap, Header header, String fileNameKey) {
        // 创建Http实例
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 创建HttpPost实例
        HttpPost httpPost = new HttpPost(url);

        // 请求参数配置
        RequestConfig requestConfig = RequestConfig.custom().setSocketTimeout(60000).setConnectTimeout(60000)
                .setConnectionRequestTimeout(30000).build();
        httpPost.setConfig(requestConfig);
        /** 标注1.这里设置header的时候不能给header里的Content-Length赋值，否则会报错 */
        // 请求header
        httpPost.addHeader(header);

        try {
            MultipartEntityBuilder builder = MultipartEntityBuilder.create();
            builder.setCharset(java.nio.charset.Charset.forName("UTF-8"));
            builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
//            builder.setMode(HttpMultipartMode.RFC6532);
            builder.setContentType(ContentType.MULTIPART_FORM_DATA);

            String fileName = multipartFile.getOriginalFilename();
            /** 标注2：此处的fileNameKey对应接收方controller处的@RequestParam(value = "file")里的名字，例如这里fileNameKey需要为file，否则接收方会报错 */
            // 文件流
            builder.addBinaryBody(fileNameKey, multipartFile.getInputStream(), ContentType.MULTIPART_FORM_DATA, fileName);
            //表单中其他参数
            if (paramMap != null && paramMap.size() > 0) {
                for (Map.Entry entry : paramMap.entrySet()) {
                    builder.addPart(entry.getKey(), new StringBody(entry.getValue(), ContentType.create("text/plain", Consts.UTF_8)));
                }
            }

            HttpEntity entity = builder.build();
            httpPost.setEntity(entity);
            // 执行提交
            log.info("文件上传httpPost:[{}]", httpPost.toString());
            HttpResponse response = httpClient.execute(httpPost);

            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                // 返回
                String res = EntityUtils.toString(response.getEntity(), java.nio.charset.Charset.forName("UTF-8"));
                return res;
            }else{
                log.error("文件请求res报错:{}", response);
            }

        } catch (Exception e) {
            log.error("调用HttpPost失败:{}", e.toString(), e);
        } finally {
            if (httpClient != null) {
                try {
                    httpClient.close();
                } catch (IOException e) {
                    log.error("关闭HttpPost连接失败！");
                }
            }
        }
        return null;
    }
}