java - HttpURLConnection 中的内容长度

Question

我正在尝试将 x-www-form-urlencoded 格式的正文发送到我的本地 Web API。我可以毫无问题地进行 GET 。这是我所做的:

    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 promised 598 bytes, but received 0

这意味着我没有在 POST 中发送任何数据，这是怎么回事？

Answer 1

使用 con.setRequestProperty("Content-Length", Integer.toString(postDataLength)); 您只需发送 postDataLength 的长度，您实际上并没有设置它的 body 。为了实际将变量发送到 Web 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();