Spring學習總結(8)-接口多個實現類的動態調用

 

需求描述：當一個接口有2個以上的實現類時，調用方需要根據參數選擇只其中一個實現類

Spring版本：5.1.8.RELEASE

 

1. 接口和實現類

/** * 接口 */ public interface OrderInfoDao { void queryOrderList(); } /** * 實現類A */ @Component public class OrderInfoDaoAImpl implements OrderInfoDao { @Override public void queryOrderList() { System.out.println("Dao A queryOrderList"); } } /** * 實現類B */ @Component public class OrderInfoDaoBImpl implements OrderInfoDao { @Override public void queryOrderList() { System.out.println("Dao B queryOrderList"); } }

　　現在要求Service層要根據參數輸入A或B動態選擇實現類。

 

2. 使用ApplicationContextAware接口實現

@Component
public class OrderInfoServiceImpl implements ApplicationContextAware { private ApplicationContext applicationContext; public void query(String username){ OrderInfoDao dao = null; if("A".equals(username)){ dao = (OrderInfoDao) applicationContext.getBean("orderInfoDaoAImpl"); } else if("B".equals(username)){ dao = (OrderInfoDao) applicationContext.getBean("orderInfoDaoBImpl"); } dao.queryOrderList(); } /** * ApplicationContextAware接口的實現類，可以拿到上下文 * @param applicationContext * @throws BeansException */ @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; } }

 

3. 使用@Autowired注入Map實現

@Component
public class OrderInfoServiceImpl {

    /**
     * 用這個方式Spring會在初始化時，自動把OrderInfoDao接口的實現類，全放到Map里
     */
    @Autowired
    private Map<String, OrderInfoDao> map;

    public void query(String username){
        // 拼接Dao實現類的名稱
        String daoName = "orderInfoDao" + username + "Impl";
        OrderInfoDao dao = map.get(daoName);
        if(dao != null){
            dao.queryOrderList();
        }
    }

}

 

4. 測試

public class OrderInfo1Test {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
        OrderInfoServiceImpl service = context.getBean(OrderInfoServiceImpl.class);
        service.query("B");
    }

}