Axis2 Client Error - NullPointerException at ClientUtils.inferIntTransport

error
java.lang.NullPointerException
at org.apache.axis2.description.ClientUtils.inferInTransport(ClientUtils.java:85)
at org.apache.axis2.description.OutInAxisOperationClient.execute(OutInAxisOperation.java:253)


environment
Attempting to connect to a web service using an Axis2 client.

possible causes:
You are missing a jar in your classpath.

solution
The missing jar is the commons-httpclient.jar. Add this jar to your classpath.