设计模式之状态模式

//封装了所有的状态
public enum StateEnum {
	CREATE(1L, "state.CreateOrderState"),
	PAY(2L, "state.PayOrderState"),
	DISPATCH(3L, "state.DispatchOrderState"),
	DONE(4L, "state.DoneOrderState");
	private Long status;
	private String clsName;
	private static final Map<Long, StateEnum> STATE_MAP;
	static {
		STATE_MAP = new HashMap<Long, StateEnum>();
		STATE_MAP.put(DISPATCH.status, DISPATCH);
		STATE_MAP.put(CREATE.status, CREATE);
		STATE_MAP.put(DONE.status, DONE);
		STATE_MAP.put(PAY.status, PAY);

	}

	private StateEnum(Long status, String clsName) {
		this.status = status;
		this.clsName = clsName;
	}
	/**
	 * 获取
	 * @param status
	 * @return
	 */
	public static StateEnum getStateEnumByStatus(Long status){
		if(status == null)
			return null;
		
		return STATE_MAP.get(status);
		
	}





// 状态变化的容器,外界不知道内部状态如何变化
public class StateContainer{
	
	private State state;
	/**
	 * 
	 * @param status
	 * @throws Exception
	 */
	public void run(Long status) throws Exception {
		StateEnum state = StateEnum.getStateEnumByStatus(status);
		if (state == null || isEmpty(state.getClsName()))
		    throw new IllegalArgumentException("status illegal!");
		Class<?> cls = Class.forName(state.getClsName());
		this.state = (State) cls.newInstance();
		doBusiness();
	}

	

	private void doBusiness() {
		this.state.execute();
	}
	
	private boolean isEmpty(String str) {
		return str == null || str.length() == 0;
	}


//定义状态的执行
public interface State {
	void execute();
}
//其中一个状态的实现
public class PayOrderState implements State{

	@Override
    public void execute() {
	    System.out.println("支付成功,准备发货.");
    }

}

//客户端代码
StateContainer bo = new StateContainer();
		bo.run(1L);
		System.out.println("-----------");
		bo.run(2L);
		System.out.println("-----------");
		bo.run(3L);
		System.out.println("-----------");
		bo.run(4L);


控制台:


订单创建成功,请支付!
-----------
支付成功,准备发货.
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已发货,做好收货准备.
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已收货,订单完成!