分别给出了post发送文件和json数据的函数，其中使用到了Jackson库来转化Json数据，使用log4j2来打印日记，可自行剔除。
public class HttpUtils { static private ObjectMapper objectMapper=new ObjectMapper(); static private Logger logger= LogManager.getLogger(); /** * 以post请求方式发送文件 * @param url * @param name 文件的请求参数名 * @param fileName 文件名 * @param fileInput 文件的输入流 * @return 默认返回参数为Json格式的数据 * @throws IOException * @throws InterruptedException */ static public Map<String,Object> postFile2(String url,String name,String fileName,InputStream fileInput) throws IOException, InterruptedException { String charset = "UTF-8"; String boundary = Long.toHexString(System.currentTimeMillis()); // Just generate some unique random value. String CRLF = "\r\n"; // Line separator required by multipart/form-data. URLConnection connection = new URL(url).openConnection(); connection.setDoOutput(true); connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary); try ( OutputStream output = connection.getOutputStream(); PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true); ) { // Send binary file. writer.append("--" + boundary).append(CRLF); writer.append("Content-Disposition: form-data; name=\""+name+"\"; filename=\"" + URLEncoder.encode(fileName,"UTF-8") + "\"").append(CRLF); writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(fileName)).append(CRLF); writer.append("Content-Transfer-Encoding: binary").append(CRLF); writer.append(CRLF).flush(); fileInput.transferTo(output); output.flush(); // Important before continuing with writer! writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary. // End of multipart/form-data. writer.append("--" + boundary + "--").append(CRLF).flush(); } // Request is lazily fired whenever you need to obtain information about response. int responseCode = ((HttpURLConnection) connection).getResponseCode(); System.out.println(responseCode); // Should be 200 //读取响应消息 BufferedReader reader=new BufferedReader(new InputStreamReader(connection.getInputStream())); StringBuilder stringBuilder=new StringBuilder(); String tempStr=null; while((tempStr=reader.readLine())!=null){ stringBuilder.append(tempStr); } //转化为JSON Map<String,Object> response= objectMapper.readValue(stringBuilder.toString(),Map.class); return response; } /** * 以post请求发送Json文件 */ public static Map<String,Object> sendJsonPost(String url,String jsonStr) throws IOException, Utils.ReceiveBadCodeException { HttpURLConnection httpURLConnection= (HttpURLConnection) new URL(url).openConnection(); //配置连接 httpURLConnection.setDoOutput(true); httpURLConnection.setRequestMethod("POST"); httpURLConnection.setRequestProperty("Content-Type","application/json;charset=UTF-8"); OutputStream out=httpURLConnection.getOutputStream(); //发送 out.write(jsonStr.getBytes("UTF-8")); //检查响应 InputStream in=httpURLConnection.getInputStream(); StringBuilder stringBuilder=new StringBuilder(); byte[] bytes=new byte[1024]; int num; while((num=in.read(bytes))!=-1){ stringBuilder.append(new String(bytes,"utf-8")); } Map<String,Object> response=objectMapper.readValue(stringBuilder.toString(),Map.class); return response; } } 参考：
文章来源: https://blog.csdn.net/jdbdh/article/details/90301077