Create a private helper method to perform a state transition

You must create a helper method which performs the state transition.

Figure 1. Creating a private helper method to perform a state transition

/**
       * Transitions this entity to the new state specified.
       *
       * @param newState
       *          the state to transition to
       * @param versionNo
       *          the version number of this entity as previously
       *          retrieved
       * @throws InformationalException
       *           if validation errors occur during the transition
       */
     private void transitionTo(
      final State<MYLIFECYCLEENTITYSTATEEntry> newState,
      final Integer versionNo) throws InformationalException {

       // get the current state of this entity
       final State<MYLIFECYCLEENTITYSTATEEntry> oldState =
         getState();

       // set the field which stores the state value
       setState(newState);

       // validate the state transition
       oldState.transitionTo(newState);

       // update the database, bypassing any pre-modify validation
        // in this class
       super.modify(versionNo);
       }

Points to note:

the validation of whether the transition is permitted is performed by the State.transitionTo method (i.e. in the line oldState.transitionTo(newState); in the figure above). See below for how to add your own validation logic; and
your entity may have overridden the modify method to add validation to be applied when calling code invokes modify - often this logic is inappropriate to state transitions, and so typically the storage of a state change is accomplished by a call to super.modify (as shown in the figure above) rather then this.modify.