java.lang.IllegalArgumentException: host parameter is null

Dear reader,

While working with Apache HttpClient you may face this error:

java.lang.IllegalArgumentException: host parameter is null
        at org.apache.commons.httpclient.HttpConnection.<init>(HttpConnection.java:206)
        at org.apache.commons.httpclient.HttpConnection.<init>(HttpConnection.java:155)
        at org.apache.commons.httpclient.SimpleHttpConnectionManager.getConnectionWithTimeout(SimpleHttpConnectionManager.java:175)
        at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:153)
        at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)
        at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)

This comes in a multi-threaded stress test, when under heavy load concurrently opening many HttpClient connections, 
intermittently receives an IllegalArgumentException with the following stack trace:

java.lang.IllegalArgumentException: host parameter is null
at org.apache.commons.httpclient.HttpConnection.<init>(HttpConnection.java:206)
at org.apache.commons.httpclient.HttpConnection.<init>(HttpConnection.java:155)
at org.apache.commons.httpclient.SimpleHttpConnectionManager.getConnectionWithTimeout(SimpleHttpConnectionManager.java:175)
at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:153)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)


Again, this issue comes only intermittently under heavy connect load. There appears some sort of timing-related error in HttpClient. 
This comes in a “multi threaded environment when there are too many instances of HttpClient” created and system is not able to resolve HostName quickly.

Solution: Set explicitly the HostConfiguration before creating the GetMethod:

    PostMethod method = null;
    HttpClient httpclient = new HttpClient();
    String theURL = YOUR_PREPARED_URL;

    HostConfiguration hf=new HostConfiguration();
    hf.setHost("http://localhost", 22);
    
    method = new PostMethod(theURL);
    method.setHostConfiguration(hf);

    LogHelper.logMessage("Before sending SMS Message: "+message);
    int respCode = httpclient.executeMethod(method);
    System.out.println("Response code:"+respCode);  //200 means successful.

So far this will eliminate this intermittent failure.

//Code is tested and works fine..