【设计模式】外观模式 ( 概念 | 适用场景 | 优缺点 | 代码示例 )

/**
 * 仓库子系统
 * 查询是否有库存
 */
public class StoreService {
    public boolean isStokeAvailable(Goods goods){
        System.out.println("校验是否有库存 : " + goods.toString() + " 有库存");
        return true;
    }
}

package kim.hsl.design.facade;
/**
 * 支付子系统
 * 支付成功返回 true
 */
public class PaymentService {
    public boolean pay(Goods goods){
        System.out.println("使用银联支付");
        return true;
    }
}

package kim.hsl.design.facade;
/**
 * 物流子系统
 * 进入发货流程 , 返回物流编号
 */
public class LogisticsService {
    public String logistics(Goods goods){
        String logisticsNo = "31415926";
        System.out.println(goods + " 进入物流系统 , 运单号为 " + logisticsNo);
        return logisticsNo;
    }
}

package kim.hsl.design.facade;
/**
 * 用户购买的统一接口
 * 用户只需要与该类进行交互
 * 该类统一处理 仓储 支付 物流 等购买流程
 */
public class BuyFacade {
    private LogisticsService logisticsService;
    private PaymentService paymentService;
    private StoreService storeService;
    public BuyFacade() {
        storeService = new StoreService();
        paymentService = new PaymentService();
        logisticsService = new LogisticsService();
    }
    /**
     * 外观类提供的访问内部三个子系统的接口
     * 客户端只需要调用该方法 , 即可完整商品购买流程
     * @param goods
     */
    public void buyGoods(Goods goods){
        if(storeService.isStokeAvailable(goods)){
            if(paymentService.pay(goods)){
                logisticsService.logistics(goods);
            }
        }
    }
}

package kim.hsl.design.facade;
/**
 * 商品
 */
public class Goods {
    private String name;
    public Goods(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "Goods{" +
                "name='" + name + '\'' +
                '}';
    }
}

package kim.hsl.design.facade;
public class Main {
    public static void main(String[] args) {
        Goods goods = new Goods("肥皂");
        BuyFacade buyFacade = new BuyFacade();
        buyFacade.buyGoods(goods);
    }
}

校验是否有库存 : Goods{name='肥皂'} 有库存
使用银联支付
Goods{name='肥皂'} 进入物流系统 , 运单号为 31415926