1         try {
 2 
 3             //聲明分割線
 4             String boundary="-----";
 5 
 6             //準備前期
 7             File file=new File(filePath);
 8             URL url=new URL("https://api.weixin.qq.com/cgi-bin/media/upload?access_token=Z_dtsiJWpgghBANNad1B9DS4sgfE9zOLmwIffYmDXDKs4ZWr6wmhX6xYNanplgB8BVsER8JFtRAnJlyc24kDiSfQwMIzIISbWKLHCkQU9ZhXYNokaZchKmA4QOtH6VoBTSBjAAAEDM&type=image");
 
 9             URLConnection urlConnection=url.openConnection();
10             urlConnection.setDoInput(true);
11             urlConnection.setDoOutput(true);
12             urlConnection.setUseCaches(false);
13             urlConnection.setRequestProperty("Connection","Keep-Alive");
14             urlConnection.setRequestProperty("Content-Type","multipart/form-data;boundary="+boundary);
 
15             urlConnection.setRequestProperty("Content-Length",String.valueOf(file.length()));
16 
17             //獲取文件輸入流
18             InputStream inputStream=new FileInputStream(file);
19             //獲取響應輸出流
20             OutputStream outputStream = urlConnection.getOutputStream();
21 
22             //
 
準備寫入頭信息
23             outputStream.write((boundary+"--\r\n").getBytes());
24             outputStream.write(("Content-Disposition:form-data;name=\"media\";filename=\""+file.getName()+"\"\r\n").getBytes());
25             outputStream.write(("Content-Type:image/jpeg\r\n\r\n").getBytes());
26             //準備循環寫入 文件流
27             byte[] b=new byte[1024];
28             int l;
29             while((l=inputStream.read(b,0,b.length))!=-1){
30                 outputStream.write(b,0,l);
31             }
32             outputStream.write(("\r\n"+boundary+"--\r\n").getBytes());
33 
34             //關閉
35             outputStream.flush();
36             outputStream.close();
37             inputStream.close();
38 
39             urlConnection.connect();
40 
41             InputStream is=urlConnection.getInputStream();
42             int c;
43             while((c=is.read())!=-1){
44                 System.out.print((char)c);
45             }
46             is.close();
47         } catch (MalformedURLException e) {
48             e.printStackTrace();
49         } catch (IOException e) {
50             e.printStackTrace();
51         }

特別註意寫入文件數據的時候，首尾都需要有分割線，並且分割線比RequestProperty裏的Content-Type裏的分割線多--個，並且註意換行

其次就是上傳的name的值為media字符串

再其次註意請求所附帶的參數

微信公眾訂閱號 上傳臨時素材示例