来源:https://www.cnblogs.com/yjmyzz/p/refactor-design-pattern-using-java8.html
java8中提供的很多新特性可以用来重构传统设计模式中的写法,下面是一些示例:
一、策略模式
上图是策略模式的类图,假设我们现在要保存订单,OrderService
接口定义要做什么,而NoSqlSaveOrderStragegy
以及MySqlSaveOrderStrategy
则提供了二种策略,分别是保存到nosql数据库,以及传统的mysql关系型数据库,最后在OrderServiceExecutor
中通过构造函数注入最终要使用的策略。
传统写法,这个场景至少得4个类,代码如下:
OrderService
接口:
public interface OrderService {
void saveOrder(String orderNo);
}
Mysql策略实现:
public class MySqlSaveOrderStrategy implements OrderService {
@Override
public void saveOrder(String orderNo) {
System.out.println("order:" + orderNo + " save to mysql");
}
}
Nosql策略实现
public class NoSqlSaveOrderStrategy implements OrderService {
@Override
public void saveOrder(String orderNo) {
System.out.println("order:" + orderNo + " save to nosql");
}
}
Spring Boot 基础就不介绍了,推荐下这个实战教程:
使用策略的辅助"容器"
public class OrderServiceExecutor {
private final OrderService service;
public OrderServiceExecutor(OrderService service) {
this.service = service;
}
public void save(String orderNo) {
this.service.saveOrder(orderNo);
}
}
运行测试类:
public class OrderServiceTest {
public static void main(String[] args) {
OrderServiceExecutor executor1 = new OrderServiceExecutor(new MySqlSaveOrderStrategy());
executor1.save("001");
OrderServiceExecutor executor2 = new OrderServiceExecutor(new NoSqlSaveOrderStrategy());
executor2.save("002");
}
}
重构后,可以省去2个策略实现类,代码如下:
public static void main(String[] args) {
OrderServiceExecutor executor1 = new OrderServiceExecutor((String orderNo) -> System.out.println("order:" + orderNo + " save to mysql"));
executor1.save("001");
OrderServiceExecutor executor2 = new OrderServiceExecutor((String orderNo) -> System.out.println("order:" + orderNo + " save to nosql"));
executor2.save("002");
}
学习资料分享:https://www.javastack.cn/study/
二、模板方法
类图如下,核心思路是把一些通用的标准方法,在抽象父类里仅定义方法签名,实现逻辑交给子类。
比如:会员系统中,每个商家都会有一些营销活动,需要推送某种信息给会员,但是不同的商家推送的内容可能不同,有些需要推送优惠券,有些需要积分通知。
抽象模板类:
public abstract class AbstractPushTemplate {
public void push(int customerId, String shopName) {
System.out.println("准备推送...");
execute(customerId, shopName);
System.out.println("推送完成\n");
}
abstract protected void execute(int customerId, String shopName);
}
优惠券的具体模板
public class PushCouponTemplate extends AbstractPushTemplate {
@Override
protected void execute(int customerId, String shopName) {
System.out.println("会员:" + customerId + ",你好," + shopName + "送您一张优惠券");
}
}
积分的具体模板
public class PushScoreTemplate extends AbstractPushTemplate {
@Override
protected void execute(int customerId, String shopName) {
System.out.println("会员:" + customerId + ",你好," + shopName + "送您10个积分");
}
}
使用示例:
AbstractPushTemplate template1 = new PushCouponTemplate();
template1.push(1, "糖果店");
AbstractPushTemplate template2 = new PushScoreTemplate();
template2.push(1, "服装店");
显然如果模板的实现方式越多,子类就越多。使用java8重构后,可以把上面的3个模板(包括抽象类模板)减少到1个,参考下面:
public class PushTemplateL