spring 4.x以上版本纔有
創建兩個帶泛型的類,並配置兩者的依賴關係,對於繼承這兩個類的子類,如果泛型相同,則會繼承這種依賴關係:
如上圖:
定義了兩個泛型base類:BaseService和BaseRepository
對於UserService和UserRpository分別繼承兩個base類,泛型都是User,則他們倆繼承了父類的依賴關係。
User:
package com.primary.spring.beans.generic.di;
public class User {
}
- BaseRepository
package com.primary.spring.beans.generic.di; public class BaseRepository <T> { public void save() { System.out.println("BaseRepository save..."); } }
- BaseService
package com.primary.spring.beans.generic.di; import org.springframework.beans.factory.annotation.Autowired; public class BaseService <T> { @Autowired protected BaseRepository<T> repository; public void add() { repository.save(); } }
- UserRepository
package com.primary.spring.beans.generic.di; import org.springframework.stereotype.Repository; @Repository public class UserRepository extends BaseRepository<User> { public void save() { System.out.println("UserRepository save..."); } }
- UserService
package com.primary.spring.beans.generic.di; import org.springframework.stereotype.Service; @Service public class UserService extends BaseService<User> { }
測試:
-
package com.primary.spring.beans.generic.di; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Main { public static void main(String[] args) { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-generic-di.xml"); UserService userService = (UserService)ctx.getBean("userService"); userService.add(); } }
beans-generic-di.xml:
-
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd"> <context:component-scan base-package="com.primary.spring.beans.generic.di"></context:component-scan> </beans>
結果:
-
在以上的代碼中,BaseService中引用了BaseReponsitory,並且在BaseService的add方法中調用了BaseReponsitory的save方法;而在他們的子類中,繼承了這種關係,因此我們在測試方法中調用userService.add(); 也是可以成功UserReponsitory中的save方法而不是BaseReponsitory的save方法。
根據泛型T自動注入相應的Reponsitory實際應用中我們可以把經常使用到的增刪改查等通用的操作些在base類中,簡化代碼。