整体思路就是通过注解在策略类上指定约定好的type,项目启动之后将所有有注解的type获取到,根据type存储,然后在业务中根据type获取对应的策略即可。本文已模拟订单业务进行演示,根据订单的type,需要不同的处理逻辑,比如,免费订单,半价订单等。
1.策略接口和实现
/**
* 处理订单策略
*/
public interface OrderStrategy {
void handleOrder(Order order);
}
@Component
@HandlerOrderType(Order.FREE) //使用注解标明策略类型
public class FreeOrderStrategy implements OrderStrategy {
@Override
public void handleOrder(Order order) {
System.out.println("----处理免费订单----");
}
}
@Component
@HandlerOrderType(Order.HALF)
public class HalfOrderStrategy implements OrderStrategy {
@Override
public void handleOrder(Order order) {
System.out.println("----处理半价订单----");
}
}
@Component
@HandlerOrderType(Order.DISCOUT)
public class DiscoutOrderStrategy implements OrderStrategy {
@Override
public void handleOrder(Order order) {
System.out.println("----处理打折订单----");
}
}
2.自定义策略注解
@Target(ElementType.TYPE) //作用在类上
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited //子类可以继承此注解
public @interface HandlerOrderType {
/**
* 策略类型
* @return
*/
int value();
}
3.业务实体
public class Order {
public static final int FREE=1; //免费订单
public static final int HALF=2; //半价订单
public static final int DISCOUT=3; //打折订单
private String name;
private Double price;
private Integer type;//订单类型
public static Order build(){
return new Order();
}
4.核心功能实现
/**
* 根据订单类型返回对应的处理策略
*/
@Component
public class HandlerOrderContext {
@Autowired
private ApplicationContext applicationContext;
//存放所有策略类Bean的map
public static Map<Integer, Class<OrderStrategy>> orderStrategyBeanMap= new HashMap<>();
public OrderStrategy getOrderStrategy(Integer type){
Class<OrderStrategy> strategyClass = orderStrategyBeanMap.get(type);
if(strategyClass==null) throw new IllegalArgumentException("没有对应的订单类型");
//从容器中获取对应的策略Bean
return applicationContext.getBean(strategyClass);
}
}
/**
* 策略核心功能,获取所有策略注解的类型
* 并将对应的class初始化到HandlerOrderContext中
*/
@Component
public class HandlerOrderProcessor implements ApplicationContextAware {
/**
* 获取所有的策略Beanclass 加入HandlerOrderContext属性中
* @param applicationContext
* @throws BeansException
*/
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
//获取所有策略注解的Bean
Map<String, Object> orderStrategyMap = applicationContext.getBeansWithAnnotation(HandlerOrderType.class);
orderStrategyMap.forEach((k,v)->{
Class<OrderStrategy> orderStrategyClass = (Class<OrderStrategy>) v.getClass();
int type = orderStrategyClass.getAnnotation(HandlerOrderType.class).value();
//将class加入map中,type作为key
HandlerOrderContext.orderStrategyBeanMap.put(type,orderStrategyClass);
});
}
}
5.业务service使用
@Component
public class OrderServiceImpl implements OrderService {
@Autowired
HandlerOrderContext handlerOrderContext;
@Override
public void handleOrder(Order order) {
//使用策略处理订单
OrderStrategy orderStrategy = handlerOrderContext.getOrderStrategy(order.getType());
orderStrategy.handleOrder(order);
}
}
6.controller测试
@RestController
@RequestMapping("/order")
public class OrderController {
@Autowired
OrderService orderService;
@GetMapping("/handler/{type}")
public void handleOrder(@PathVariable Integer type){
Order order = Order.build()
.add("name", "微信订单")
.add("price", 99.9)
.add("type", type);
orderService.handleOrder(order);
}
}
7.测试
再添加策略添加实现类,启用注解即可!省去了工厂模式,直接用注解实现,避免修改工厂类,这里贴一个我们之前项目的工厂类实现:
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