贯穿设计模式-责任链模式

样例代码

涉及到的项目样例代码均可以从https://github.com/WeiXiao-Hyy/Design-Patterns.git获取

需求

实时地，根据city，sex，product字段进行业务投放，比如：北京的男生；四川的电脑等等 → 责任链模式（责任链表模式）

UML图

handler自身含有next指针和链表类似，使用Apollo进行动态配置字段进行规则变更

Apollo访问不到内网地址

由于Apollo使用Docker进行安装，导致Apollo访问不到configserver的地址

app:
  id: DesignPatternLearning

# apollo
apollo:
  meta: "http://localhost:8080"
  bootstrap:
    enabled: true
    eagerLoad:
      enabled: true
  cacheDir:
    "/Users/hujiale/GitCode/Apoll"

logger:
  level:
    com:
      info

执行时在JVM参数添加-Dapollo.configService=http://localhost:8080即可解决

核心代码

//组装责任链条并返回责任链条首节点
private AbstractBusinessHandler buildChain() {

    //如果没有配置,直接返回null
    if (Objects.isNull(this.handlerType)) {
        return null;
    }

    if (Objects.isNull(this.currentHandlerType)) {
        this.currentHandlerType = this.handlerType;
    }

    if (this.currentHandlerType.equals(this.handlerType) && Objects.nonNull(this.currentHandler)) {
        return this.currentHandler;
    } else {
        log.info("config modified or first init, start to assemble duty chain.");
        synchronized (this) {
            try {
                //伪头节点
                AbstractBusinessHandler dummyHeadHandler = new CityHandler();
                AbstractBusinessHandler preHandler = dummyHeadHandler;

				//采用反射实例化责任链节点
                String[] handlerTypeList = this.handlerType.split(",");
                for (String handlerType : handlerTypeList) {
                    AbstractBusinessHandler handler = (AbstractBusinessHandler)
                            Class.forName(HandlerEnum.valueOf(handlerType).getValue()).newInstance();
                    preHandler.nextHandler = handler;
                    preHandler = handler;
                }
                
				// 初始化类中变量
                this.currentHandler = dummyHeadHandler.nextHandler;
                this.currentHandlerType = this.handlerType;

                return this.currentHandler;
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
                throw new UnsupportedOperationException(e);
            }
        }
    }
}