java.io.IOException: Received authentication challenge is null in ICS 4.0.3

Question

I\'m trying to logoff from the server. But it returns \"0\" response code with this exception. I\'m using GET verb to do this.

LogCat

10-17 14         


        

Answer 1

You can get the response code after an exception if you call .getResponseCode() a second time on the connection object. This is because the first time you call .getResponseCode() an internal state is set that enables .getResponseCode() to return without throwing an exception.

Example:

HttpURLConnection connection = ...;
try {
    // Will throw IOException if server responds with 401.
    connection.getResponseCode(); 
} catch (IOException e) {
    // Will return 401, because now connection has the correct internal state.
    int responsecode = connection.getResponseCode(); 
}

I have also answered this question here: https://stackoverflow.com/a/15972969/816017

Answer 2

This error happens beause the server sends a 401 (Unauthorized) but does not give a "WWW-Authenticate" which is a hint for the client what to do next. The "WWW-Authenticate" Header tells the client which kind of authentication is needed (either Basic or Digest). This is usually not very useful in headless http clients, but thats how the standard is defined. The error occurs because the lib tries to parse the "WWW-Authenticate" header but can't.

Possible solutions if you can change the server:

• Add a fake "WWW-Authenticate" header like: WWW-Authenticate: Basic realm="fake". This is a mere workaround not a solution, but it should work and the http client is satisfied.
• Use HTTP status code 403 instead of 401. It's semantic is not the same and usually when working with login 401 is a correct response (see here for detailed discussion) but its close enough.

Possible solutions if you can't change the server:

As @ErikZ wrote in his post you could use a try&catch

HttpURLConnection connection = ...;
try {
    // Will throw IOException if server responds with 401.
    connection.getResponseCode(); 
} catch (IOException e) {
    // Will return 401, because now connection has the correct internal state.
    int responsecode = connection.getResponseCode(); 
}

I also posted this here: java.io.IOException : No authentication challenges found

Answer 3

HttpURLConnection.getResponseCode() throws java.io.IOException: Received authentication challenge is null when it encounters malformed HTTP 401 header. Do you receive WWW-Authenticate and Content-Length headers from server in addition to HTTP/1.1 401 Unauthorized header? See IOException: "Received authentication challenge is null" (Apache Harmony/Android)

If you can't make changes to server, then you can catch that exception (thanks https://stackoverflow.com/a/10904318/262462)

try {
    response=connection.getResponseCode();
}
catch (java.io.IOException e) {
    if (e.getMessage().contains("authentication challenge")) {
        response = HttpsURLConnection.HTTP_UNAUTHORIZED;
    } else { throw e; }
}