策略模式

在业务系统中，可能根据某个值的不同，进行不同的逻辑代码，如下：

public void process(OrderDto orderDto){
        int type = orderDto.getType();
        if (1==type){
            System.out.println("取消即时订单");
        }else if (2==type){
            System.out.println("取消预约订单");
        }
    }

若干个月再来看可能就有点看不懂了。

此时我们采用策略模式

1、定义抽象类

public abstract class AbstractStrategy {
    abstract  public void process(OrderDto orderDto);
}

2、根据不同的类型，实现具体的业务代码

public class InstantOrderStrategy extends AbstractStrategy{
    private static volatile  InstantOrderStrategy instantOrderStrategy = null;
    @Override
    public void process(OrderDto orderDto) {
　　　　//具体的业务代码。。。。。。
        System.out.println(orderDto.getDesc());
    }

    /**
     * 单例模式
     * @return
     */
    public static InstantOrderStrategy getInstance(){
        if (null==instantOrderStrategy){
            synchronized (InstantOrderStrategy.class){
                if (null==instantOrderStrategy){
                    instantOrderStrategy = new InstantOrderStrategy();
                }
            }
        }
       return instantOrderStrategy;
    }

 

3、定义枚举类，列举类型

public enum OrderTypeEnum {
    INSTANT(1,"取消及时订单", InstantOrderStrategy.getInstance()),
    BOOKING(2,"取消预约订单", BookingOrderStrategy.getInstance()),
    ;

    private final Integer code;

    private final String desc;

    private final AbstractStrategy abstractStrategy;

    OrderTypeEnum(Integer code, String desc,AbstractStrategy abstractStrategy) {
        this.code = code;
        this.desc = desc;
        this.abstractStrategy = abstractStrategy;
    }

    public static OrderTypeEnum valueOf(Integer code){
        for (OrderTypeEnum orderTypeEnum : OrderTypeEnum.values()) {
            if (orderTypeEnum.code.equals(code)){
                return orderTypeEnum;
            }
        }
        return null;
    }
    public Integer getCode() {
        return code;
    }

    public String getDesc() {
        return desc;
    }

    public AbstractStrategy getAbstractStrategy() {
        return abstractStrategy;
    }

4、调用代码

public class CancelOrderStrategyService {

    public void cancelOrder(OrderDto orderDto) throws IllegalAccessException, InstantiationException {
　　　　//根据type获取指定的业务处理类
        AbstractStrategy abstractStrategy = OrderTypeEnum.valueOf(orderDto.getType()).getAbstractStrategy();
        abstractStrategy.process(orderDto);
    }
}