HttpURLConnection: java.lang.IllegalStateException: Already connected

Question

I\'m trying to use HttpURLClient to send some POST data to a server using the HttpRestClient class shown below. When executing

conn.setDoInput(true)         


        

Answer 1

This might be due to watches while debugging in your IDE. See this answer. It happened to me and was hard to discover.

Answer 2

It may be a misleading exception. See this defect for Jersey-2 https://java.net/jira/browse/JERSEY-2729

The link has been updated: https://github.com/jersey/jersey/issues/3001

Basically the issue is jersey was throwing invalid exception. The real issue in my case was that the connection was refused from the server.

Answer 3

You called both of conn.setDoInput(true); and conn.setDoOutput(true);. Use one of them:

• setDoOutput(true) is used for POST and PUT requests.
• setDoInput(true) is used for GET request.

The connection you made was confused, it can't decide which request should be used.

In your code:

static public int post(String urlStr, List<NameValuePair> data){
    HttpURLConnection conn = null;
    System.setProperty("http.keepAlive", "false"); // must be set
    try {
        ...
        conn.setDoOutput(true);
        conn.setRequestMethod("POST");
        // and connect to server, if needed
        conn.connect();
        ...
    }
....