【问题解决】HttpURLConnection如何以POST的方式发送请求，传递form表单格式的数据到外部接口

JAVA对接外部接口（无视凭证）

问题点：

• 给到图片URL，需要将图片先下载下来，然后以流的形式（form表单的数据格式）传给外部接口
• 对方域名证书过期

package com.jeesite.test;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.security.cert.X509Certificate;

public class FileUpload {

    public static void main(String[] args) {
        String imgURL = "你的图片地址";
        String FILE_UPLOAD_URL = "外部接口地址";
        String token = "请求接口校验的token";

        try {
            //处理图片链接获取名字方法工具类，可以忽略
            String imgName = getImgName(imgURL);

            // 忽略证书验证（就是这一段）
            TrustManager[] trustAllCerts = new TrustManager[]{
                    new X509TrustManager() {
                        public X509Certificate[] getAcceptedIssuers() {
                            return null;
                        }
                        public void checkClientTrusted(X509Certificate[] certs, String authType) {}
                        public void checkServerTrusted(X509Certificate[] certs, String authType) {}
                    }
            };

            SSLContext sc = SSLContext.getInstance("SSL");
            sc.init(null, trustAllCerts, new java.security.SecureRandom());
            HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());

            HostnameVerifier allHostsValid = (hostname, session) -> true;
            HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);

            // 请求地址
            URL url = new URL(FILE_UPLOAD_URL);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            //这个可要可不要，看自己
            connection.setRequestProperty("Cookie", "SESSION=MzVhOTJlMzMtZmZjMy00M2Y5LTk1NDAtNDNlMzVjMWVlMTIw");
            //注意数据格式
            connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");
			//用于分隔多个实体（如文件、表单字段等）的标识符（HTTP协议中，不太了解的话自行知识填充）
            String boundary = "----WebKitFormBoundary7MA4YWxkTrZu0gW";
            OutputStream outputStream = connection.getOutputStream();

            // 文件部分
            outputStream.write(("--" + boundary + "\r\n").getBytes());
            outputStream.write(("Content-Disposition: form-data; name=\"file\"; filename=\"" + imgName + "\"\r\n").getBytes());
            outputStream.write(("Content-Type: image/png\r\n\r\n").getBytes());
            InputStream inputStream = new URL(imgURL).openStream();
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
            inputStream.close();
            outputStream.write(("\r\n").getBytes());

            // parentId部分
            outputStream.write(("--" + boundary + "\r\n").getBytes());
            outputStream.write(("Content-Disposition: form-data; name=\"parentId\"\r\n\r\n").getBytes());
            outputStream.write(("huanwei\r\n").getBytes());

            // name部分
            outputStream.write(("--" + boundary + "\r\n").getBytes());
            outputStream.write(("Content-Disposition: form-data; name=\"name\"\r\n\r\n").getBytes());
            outputStream.write((""+imgName+"\r\n").getBytes());

            // 结束
            outputStream.write(("--" + boundary + "--\r\n").getBytes());
            outputStream.flush();
            outputStream.close();

            // 读取响应
            int responseCode = connection.getResponseCode();
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String inputLine;
            StringBuilder response = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            JSONObject jsonObject = JSON.parseObject(response.toString());
            System.out.println(jsonObject);


        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static String getImgName(String imgURL) {
        return imgURL.substring(imgURL.lastIndexOf("/") + 1);
    }
}
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闹了个笑话，在和三方对接的时候我一直连不通对方的接口，甚至一度怀疑他们的接口有问题，差点吵起来。。后面发现自己电脑连了VPN，尼玛！断了一下接口就通了 服了= =