getStateValue
Description: Access a processor's state values by passing in the String key and getting the value back as a String. This is a special Expression Language function that only works with processors that explicitly allow EL to query state. Currently only UpdateAttribute does.
Subject Type: No Subject
Arguments:
Key : The key to use when accessing the state map.
Return Type: String
Examples: UpdateAttribute processor has stored the key
"count" with value "20" in state.
'${getStateValue("count")}` returns 20.