HttpURLConnection 中的内容长度

Question

我正在尝试将x-www-form-urlencoded 中的正文发送到我的本地 Web API。我可以毫无问题地制作GET。这是我的工作：

    String urlParameters = "user=User&label=GPU+Temp&file=src%2FDataSource0.txt&backgroundColor=rgb(255%2C255%2C255%2C0)&borderColor=rgb(255%2C255%2C255%2C0)&pointBorderColor=rgb(255%2C255%2C255%2C0)&pointHoverBackgroundColor=rgb(255%2C255%2C255%2C0)&pointHoverBorderColor=rgb(255%2C255%2C255%2C0)&min=0&max=100&stepSize=50";

    byte[] postData = urlParameters.getBytes(Charset.forName("UTF-8"));
    int postDataLength = postData.length;
    String request = "http://192.168.1.30:6262/api/values";
    URL url = new URL(request);
    con = (HttpURLConnection) url.openConnection();
    con.setDoOutput(true);
    con.setInstanceFollowRedirects(false);
    con.setRequestMethod("POST");
    con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
    con.setRequestProperty("charset", "utf-8");
    con.setRequestProperty("Content-Length", Integer.toString(postDataLength));
    con.connect();

java.net.ProtocolException: content-length 承诺 598 字节，但收到 0

所以这意味着我没有在我的POST 中发送任何数据，怎么会？

Answer 1

使用con.setRequestProperty("Content-Length", Integer.toString(postDataLength)); 只是发送postDataLength 的长度，实际上并没有设置它的主体。为了真正将您的变量发送到网络服务，您需要在调用 connect() 之前执行此操作：

OutputStream os = con.getOutputStream();
os.write(urlParameters.getBytes("UTF-8"));
os.close();

Answer 2

你需要这样做：

            body = datos.toString();
            content_bytes = body.getBytes("UTF-8");
            content_length = content_bytes.length;



            // establecer headers.
            connection.setRequestProperty( "Content-Type", "application/json; charset=utf-8" );
            connection.setRequestProperty( "Content-Length", Integer.toString( content_length  ) );

.....

            dataOutputStream = new DataOutputStream( connection.getOutputStream() );
            dataOutputStream.write(body.getBytes("UTF-8"));