Java策略模式Demo

当我们的业务逻辑根据不同的场景要做不同的处理时，需要大量的if判断加处理，这样导致代码臃肿且拓展性低；下面我用一个简单的业务，使用策略模式去处理不同的场景；业务场景为在IM聊天中，根据不同的消息类型，去处理不同的消息。

1.定义处理接口

public interface MessageHandler {
    void handle(MsgContext param);
}

2.创建各业务实现handler

@Component
@MessageTypeAnnotation(MessageType.TEXT)
public class TextMessageHandler implements MessageHandler {
    @Override
    public void handle(MsgContext param) {
        System.out.println("TextMessageHandler="+param.getMsg());
    }
}

3.创建类型枚举

public enum MessageType {
    TEXT,
    VIDEO
}

4.创建自定义注解MessageTypeAnnotation

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface MessageTypeAnnotation {
    MessageType value() default MessageType.TEXT;
}

5.创建参数上下文对象

@Data
public class MsgContext {
    private MessageType messageType;
    private String msg;
}

6.创建消息handler工厂

@Component
public class MeaasgeFactory {
    private Map<MessageType, MessageHandler> handlerMap = new ConcurrentHashMap<>();
 
    @Autowired
    public void init(Map<String, MessageHandler> handlerMaps) {
        handlerMap.clear();
        handlerMaps.keySet().stream().forEach(beanName -> {
            Class<? extends MessageHandler> aClass = handlerMaps.get(beanName).getClass();
            MessageTypeFlag annotation = aClass.getAnnotation(MessageTypeFlag.class);
            if (annotation != null) {
                handlerMap.put(annotation.value(), handlerMaps.get(beanName));
            }
        });
    }
 
    public MessageHandler getHandler(MessageType type) {
        if (handlerMap == null) {
            return null;
        }
        return handlerMap.get(type);
    }
}

7.单元测试

@Resource
private MeaasgeFactory meaasgeFactory;
 
@GetMapping("/test")
public WebResponse<BrandRelationResult> test(MsgContext param) {
    MsgContext msgContext = new MsgContext();
    msgContext.setMessageType(MessageType.VIDEO);
    msgContext.setMsg("我是文本");
    MessageHandler handler = meaasgeFactory.getHandler(msgContext.getMessageType());
    handler.handle(msgContext);
    return null;
}