Using JConsole delivered with Java 6, try to create a connection without specifying any username or password, just a JMX Service URL in the connection dialog.

The underlying connector will receive a jmx.remote.credentials key in the connection environment when being connected [JMXConnector.connect(env)], the value being a String[2] object with each element being empty.

This is a behaviour change over Java 5 where, in such a case, the credentials were null in the connection environment at the connection time.

Since a connector can receive some JMX credentials both when created or when connected, the latest overriding the first, the username and password will always be empty even when initially set at the construction time.

This defect is about rolling back to the behaviour of Java 5 for backwards comptability reasons, considering the interest of providing an array of empty strings at connection time is questionable when the username and password are not specified.