应用场景

通常在我们需要new多个对象的时候，需要写很多个if else分支，根据不同场景来创建对象；我们可以通过初始化方式，批量创建对象。通常有如下3种形式：

先看一个具体场景例子，我们需要根据不同topic创建具体topic的实现子类，不想写几十个if/else；

方式一clazz.newInstance

  1.    DISPATCH_INFO(RetryBizEnum.DISPATCH_INFO.getValue(), FullBizCodeEnum.D1003, OrderSyncDispatchInfoConsumer.TOPIC, OrderSyncDispatchInfoConsumer.class);
  4.     /**
  5.      * 处理类bean
  6.      */
  7.     private final Class<AbstractConsumerBase> dealBean;
  10.     ConsumerEnum(int bizType, FullBizCodeEnum bizCode, String topic, Class dealBean) {
  11.         this.bizType = bizType;
  12.         this.bizCode = bizCode;
  13.         this.topic = topic;
  14.         this.dealBean = (Class<AbstractConsumerBase>) dealBean;
  15.     }
  18.     for (ConsumerEnum type : ConsumerEnum.values()) {
  19.                     Class<AbstractConsumerBase> clazz = type.getDealBean();
  20.                     AbstractConsumerBase person = clazz.newInstance();
  21.                     dealMap.put(type.getTopic(), person);
  22.                 }

方式二-直接new方式

  1. DISPATCH_INFO(RetryBizEnum.DISPATCH_INFO.getValue(), FullBizCodeEnum.D1003, OrderSyncDispatchInfoConsumer.TOPIC, new OrderSyncDispatchInfoConsumer());
  3.     /**
  4.      * 处理类bean
  5.      */
  6.     private final AbstractConsumerBase dealBean;
  9.         ConsumerEnum(int bizType, FullBizCodeEnum bizCode, String topic, AbstractConsumerBase dealBean) {
  10.         this.bizType = bizType;
  11.         this.bizCode = bizCode;
  12.         this.topic = topic;
  13.         this.dealBean = (AbstractConsumerBase) dealBean;
  14.     }
  17.                 for (ConsumerEnum type : ConsumerEnum.values()) {
  18.                     dealMap.put(type.getTopic(),  type.getDealBean());
  20.                 }

后面使用静态工厂方式进行封装

  1. package com.yougou.ordercenter.web.listener.kafka.topic.base;
  3. import com.yougou.framework.logger.Logger;
  4. import com.yougou.framework.logger.LoggerFactory;
  6. import java.util.HashMap;
  7. import java.util.Map;
  9. /**
  10.  * 静态工厂模式
  11.  *
  12.  * @author david
  13.  * @site www.belle.net.cn
  14.  * @company 百丽国际
  15.  * @Date 创建时间：2022-04-13 21:36
  16.  */
  17. public class ConsumerFactory {
  19.     private static final Logger logger = LoggerFactory.getLogger(ConsumerFactory.class);
  21.     // 把topic对应的具体处理类，关系映射
  22.     private static final Map<String, AbstractConsumerBase> dealMap = new HashMap<>(ConsumerEnum.values().length);
  24.     static {
  25.         try {
  26.             for (ConsumerEnum type : ConsumerEnum.values()) {
  27.                 dealMap.put(type.getTopic(), type.getDealBean());
  28.             }
  29.         } catch (Exception e) {
  30.             logger.error("实例化ConsumerFactory工厂类异常" + e.getMessage(), e);
  31.         }
  32.     }
  34.     /**
  35.      * 通过topic获取具体实现类
  36.      *
  37.      * @param topic
  38.      * @return
  39.      */
  40.     public static AbstractConsumerBase create(String topic) {
  41.         return dealMap.get(topic);
  42.     }
  43. }