final String newLine = "\r\n";

final String boundaryPrefix = "--";

// 定义数据分隔线

String BOUNDARY = "============" + "1234567890" + "============";

// 服务器的域名

URL url = new URL(urls); // 建立http连接

System.out.println("url:"+url); // 创建url资源

HttpURLConnection conn = (HttpURLConnection) url.openConnection(); // 设置允许输出

conn.setRequestMethod("POST"); // 设置维持长连接

conn.setDoOutput(true); // 设置允许输入

conn.setDoInput(true); // 设置不用缓存

conn.setUseCaches(false); // 设置传递方式

conn.setRequestProperty("Connection", "Keep-Alive"); // 设置文件字符集:

conn.setRequestProperty("Charset", "UTF-8"); // 转换为字节数组

conn.setRequestProperty("Content-Type","multipart/form-data; boundary=" + BOUNDARY);

//获取图片URL

imgUrl = new String(readFromUrl(storageUrl),"UTF-8");

byte[] imgByte = readFromUrl(imgUrl);

System.out.println("imgUrl:" + imgUrl);

// 上传文件

StringBuilder sb = new StringBuilder();

StringBuffer sb1=new StringBuffer();

sb.append(boundaryPrefix);

sb.append(BOUNDARY);

sb.append(newLine);

// 文件参数

sb.append("Content-Disposition: form-data;name=\"image\";filename=\"" + imgUrl +"\"");

sb.append(newLine);

sb.append("Content-Type:"+URLConnection.guessContentTypeFromName(imgUrl));

// 参数头设置完以后需要两个换行，然后才是参数内容

sb.append(newLine);

sb.append(newLine);

System.out.println("-----111111-----");

conn.connect();

OutputStream out = new DataOutputStream(conn.getOutputStream());

byte[] head = sb.toString().getBytes("utf-8");

out.write(head);

System.out.println("sb:\n\r");

System.out.println(sb.toString());

InputStream in = new URL(imgUrl).openStream();

byte[] bufferOut = new byte[1024];

int bytesRead = -1;

while ((bytesRead = in.read(bufferOut)) != -1) {

out.write(bufferOut, 0, bytesRead);

}

in.close();

System.out.println(imgUrl);

byte[] foot = ("\r\n" + boundaryPrefix + BOUNDARY + boundaryPrefix + "\r\n").getBytes("utf-8");

System.out.println("\r\n" + boundaryPrefix + BOUNDARY + boundaryPrefix + "\r\n");

out.write(foot);

out.flush();

out.close();

LOG是：

tomcat default url:https://api.weixin.qq.com/wxa/msg_sec_check?access_token=31_XXXXXXXXNIQ

tomcat default imgUrl:https://XXX/9D9000001B78E1F0014601F49.jpg

tomcat default -----111111-----

tomcat default sb:

tomcat default

tomcat default --============1234567890============

tomcat default Content-Disposition: form-data;name="image";filename="https://XXX/9D9000001B78E1F0014601F49.jpg"

tomcat default Content-Type:image/jpeg

tomcat default

tomcat default https://XXX/9D9000001B78E1F0014601F49.jpg

tomcat default

tomcat default --============1234567890============--