State Diagrams
A state diagram describes the life history of objects of a given class.
A state diagram is used to show the following:
The state space of a given class
The events that cause a transition from one state to another
The actions that result from a state change
A state diagram is a directed graph of states connected by transitions.
State Notation
A state is a condition in which an object can reside during its lifetime while it satisfies some condition, performs an activity, or waits for an event. A state icon is a rounded rectangle with a name and a compartment.
For example, Figure D.7 shows the state diagram of a stateful session bean instance. It consists of three states: Instance does not exist, Ready, and Passive.
Figure D.7. State diagram example.
Transition Notation
A transition is a relationship between two states. It indicates that an object in the first state will perform certain actions, and will then enter the second state when a given event occurs. The icon for a state transition is a line with an arrowhead pointing toward the next state. For example, Figure D.7 shows that the object in the Ready state enters the Passive state when the ejbPassivate() event occurs.