在之前的书城案例中，service层中的UserService和BookService分别在各自的类中定义UserDao和BookDao并调用各自的save()方法进行数据的保存；使用注解关键字@Autowired实现类型的自动装配： @Autowired原理： @Autowired private BookService bookService; 1、先按照类型去容器中去找对应的组件：bookService=ioc.getBean(BookService.class); (1）找到一个就赋值； (2）没找到抛异常； (3）找到多个（子类继承）： 1）、再按照变量名作为id继续匹配去找BookService(bookService)、BookServiceExt(bookServiceExt) a、匹配上 b、没有匹配上，报错 原因：按照变量名继续匹配 使用Qualified:指定一个名作为id，让spring别使用变量名作为id @Autowired(required = false)：找不到装配null
为了简化这种重复的调用工作，引入泛型依赖注入，UserDao和BookDao同时继承自BaseDao（dao层的一个抽象的泛型类），UserService和BookService同时继承自BaseService(service层的泛型类)。
BaseDao
package com.xyb.fourth.dao; public abstract class BaseDao<T> { public abstract void save(); } UserDao package com.xyb.fourth.dao; import com.xyb.fourth.bean.User; import org.springframework.stereotype.Repository; @Repository public class UserDao extends BaseDao<User> { @Override public void save() { System.out.println("正在保存用户..."); } } BookDao package com.xyb.fourth.dao; import com.xyb.fourth.bean.Book; import org.springframework.stereotype.Repository; @Repository public class BookDao extends BaseDao<Book> { @Override public void save() { System.out.println("正在保存图书..."); } } BaseService package com.xyb.fourth.service; import com.xyb.fourth.dao.BaseDao; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; public class BaseService<T> { @Autowired BaseDao<T> baseDao; public void save(){ System.out.println("自动注入的dao"+baseDao); baseDao.save(); } } BookService package com.xyb.fourth.service; import com.xyb.fourth.bean.Book; import com.xyb.fourth.dao.BaseDao; import com.xyb.fourth.dao.BookDao; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service public class BookService extends BaseService<Book> { } UserService package com.xyb.fourth.service; import com.xyb.fourth.bean.User; import com.xyb.fourth.dao.UserDao; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service public class UserService extends BaseService<User>{ } IOC单元测试 package com.xyb.fourth.test; import com.xyb.fourth.service.BookService; import com.xyb.fourth.service.UserService; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class IOCTest { ApplicationContext ioc=new ClassPathXmlApplicationContext("ioc.xml"); @Test public void test23(){ BookService bookService=ioc.getBean(BookService.class); UserService userService=ioc.getBean(UserService.class); bookService.save(); userService.save(); System.out.println(bookService.getClass().getGenericSuperclass()); System.out.println(userService.getClass().getGenericSuperclass()); } }具体的逻辑关系图如下：
