|Event
___currentState__|______newState___

public class Running extends StateT{

  //
  public void run(StateOwner stateOwner){
     stateOwner.setCurrentState(this);
  }

  //转换到下一个状态的规则
  //当前是Running状态，下一个状态可能是暂停、结束或者强制退出等
  //状态，但是绝对不会是Not_Started这样的状态
  //转换规则在这里得到了体现。
  public State next(Event e) {
    if(transitions == null){
       addEventState(new EventImp("PAUSE"), new Suspended());
       addEventState(new EventImp("END"), new Completed());
       addEventState(new EventImp("STOP"), new Aborted());
    }
    return super.next(e);
  }

}     



外界直接调用 StateMachine的关键方法transition；实行状态的自动转变。  


public class StateMachine {

 /**
   * 状态切换
   * 根据Event参数，运行相应的状态。
   * 1. 获得当前状态
   * 2. 使用当前状态的next()转换
   *                  |Event
   * ___currentState__|______newState___
   *
   * @param inputs
   */
  public final void transition(String taskid, Event e) throws Exception {
    State currentState = readCurrentState(taskid); //从数据库获得当前状态
    StateOwner stateOwner = new StateOwner(taskid, currentState);
    //转换状态
    currentState = currentState.next(e);
    if (currentState != null) {
      currentState.run(stateOwner);
      saveCurrentState(stateOwner); //保存当前状态
    }
  }

} 

 public State next(Event e) throws InvalidStateException{
    logger.debug(" transitions size = " + transitions.size());
    String name = e.getName();
    if (transitions.containsKey(name))
      return (State) transitions.get(name);
    else
      throw new RuntimeException("Input not supported for current state "
                                 + " state is " + this.getClass().getName()
                                 + " Event is " + e.getName() );
  }