Servlet post to server using HttpUrlConnection

[Nicky Eng]

Hi there,


In my servlet I will send data to a URL using method 'POST' with HttpUrlConnection class.

But it happens to return me http code=411 from server which indicates content-length field.

I try to send few data like "userid=username&pass=1234&msg=try+again"

Here is my part of code:

  
    URL url;
    HttpURLConnection connection = null;  
    try {
      //Create connection
      url = new URL(targetURL);
      connection = (HttpURLConnection)url.openConnection();
      connection.setRequestMethod("POST");
      connection.setDoOutput(true);
      connection.connect();

      int return_code = connection.getResponseCode();
      System.out.println("return_code"+return_code);
      
      } catch (Exception e) {

      e.printStackTrace();
      return null;

     } finally {

      if(connection != null) {
        connection.disconnect(); 
      }
    }
  

My question is

1: Does content-length field is necessary in a POST method ?
2: Even if I coded "connection.setRequestProperty("Content-length", length) " after connection.setRequestMethod("POST"), It will give me NO return_code value. Why?


Can anyone please help me..i'm stuck for few days..


thanks in advance.

Nick

[William Brogden]

1. Content-length is not generally necessary but since you got a 411, the service you are calling requires it.
2. NO return value means what? did that print statement even execute?

Where did you write the body of the POST?

Bill

[Nicky Eng]

William Brogden wrote:1. Content-length is not generally necessary but since you got a 411, the service you are calling requires it.
2. NO return value means what? did that print statement even execute?

Where did you write the body of the POST?

Bill

String params = "?Userid=username&pass=1234";

URL server = null;
server = new URL(protocol, serverName, Integer.valueOf(port), "/response.aspx" + params);   

params string contents the body...


Is that the way of posting params to server using POST method?

[Nicky Eng]

I've try again this morning but this time i added in content-length...but it wont retun me the response http code

 URL url;  
     HttpURLConnection connection = null;    
     try {  
       //Create connection  
       url = new URL(targetURL);  
       connection = (HttpURLConnection)url.openConnection();  
       connection.setRequestMethod("POST");  
       connection.setRequestProperty("Content-length", params.length());    // added in this line
       connection.setDoOutput(true);  
       System.out.println("b4 calling connect()");
       connection.connect();  
       System.out.println("after calling connect()");

       int return_code = connection.getResponseCode();  
       System.out.println("return_code:"+return_code);  
         
       } catch (Exception e) {  
   
       e.printStackTrace();  
       return null;  
   
      } finally {  
          if(connection != null) {  
         connection.disconnect();   
       }  
     }  

The result is :

b4 calling connect()
after calling connect()

"return_code" is not printed.
I dont understand, why it cannot return me the value of response code?

anyone help ?

Nick

[Rok Štelcer]

Hi,

On the first look, I would say that the API call getResponseCode() throws IOException.

Try to replace the existing call (Exception block):
- e.printStackTrace(); // standard error stream
with the following one:
- System.out.println("Exception : " + e.toString()); // standard output stream
and let us know the result.



Regards,
Rok

[William Brogden]

I dont think that URL constructor works the way you are trying to use it.

Surely that last parameter

  "/response.aspx" + params  

creates a String which is NOT a file name and a MalformedURLException is thrown.

Bill

[Rob Spoor]

I don't think so. That would cause the "b4 calling connect()" and "after calling connect()" to not be printed, as they come after the construction of the URL.

Nicky, I just want to know: is the getResponseCode() method "hanging", or is an exception thrown and printed?

And Rok, the full stack trace is always more useful for debugging than just the toString() value which is just the class and message. The stack trace also indicates exactly where the exception is thrown from.

[cmscreativeguy Kumar]

Check this COde ... ITs working for me :)

URL url = null;
String result = "";
HttpURLConnection connection = null;
try{
//Create connection
url = new URL(desiredUrl);

connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type","text/html");
connection.setRequestProperty("Connection", "Keep-Alive");
connection.setRequestProperty("Content-Length", Integer.toString("your message length here ".length()));
connection.setAllowUserInteraction(true);
connection.setRequestProperty("Protocol-Version",httpVersion);
connection.setUseCaches(false);
connection.setDoInput(true);
connection.setDoOutput(true);


if(connection.getResponseCode() == 200)
{
OutputStreamWriter wr = new OutputStreamWriter(connection.getOutputStream());
wr.write(jsonText);
wr.flush();
wr.close();

// get data
BufferedReader rd = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String line;
while ((line = rd.readLine()) != null) {
// Process line...
// Print HERE
}
rd.close();

}

} catch (Exception e)
{

e.printStackTrace();
}finally{
if(connection != null) {
connection.disconnect();
}
}