springioc之泛型依赖注入_htkzs的博客-爱代码爱编程

首先讲解一下原始的注入方式

public abstract class BaseDao<T> {
    public abstract void save();
}

@Repository
public class BookDao extends BaseDao<Book>{
    @Override
    public void save() {
        System.out.println("保存图书信息 BookDao被调用");
    }
}

@Repository
public class StudentDao extends BaseDao<Student>{

    @Override
    public void save() {
        System.out.println("保存用户信息 StudentDao被调用");
    }
}

@Service
public class BookService {
    @Autowired
    private BookDao bookdao;
    public void saveBook(){
        bookdao.save();
    }
}

@Service
public class StudentService {
    @Autowired
    private StudentDao studentDao;
    public void saveStudent(){
        studentDao.save();
    }
}

@ContextConfiguration(locations = "classpath:application02.xml")
@RunWith(SpringJUnit4ClassRunner.class)
public class SpringJunit4Test {
    @Autowired
    private BookService bookService;
    @Autowired
    private StudentService studentService;
    @Test
    public void save(){
        bookService.saveBook();
        studentService.saveStudent();
    }
}
通过测试发现要调用那个具体的持久层Dao都需要，注入具体的Dao 而下来的操作就是通过泛型动态决定要注入那个Dao进行操作。
注意：下面没出现的Dao层代码和上面的代码保持一致。

@Service
public class BookService extends BaseService<Book>{

}

@Service
public class StudentService extends BaseService<Student>{

}

public class BaseService<T> {
    @Autowired
    private BaseDao<T> baseDao;
    public void save(){
        baseDao.save();
    }
}
通过泛型决定注入具体调用的那个Dao
@ContextConfiguration(locations = "classpath:application02.xml")
@RunWith(SpringJUnit4ClassRunner.class)
public class SpringJunit4Test {
    @Autowired
    private BaseService<Student> baseService;
    @Test
    public void save(){
        baseService.save();
        System.out.println(baseService.getClass().getSuperclass());
        //得到带泛型的类的类型名称
        System.out.println(baseService.getClass().getGenericSuperclass());
    }
}

由此可见，当我们传入一个具体的泛型Student后，调用底层的save()就会在BaseService中自动注入StudentDao 进而调用StudentDao的save()方法

Spring在做依赖注入的时候，泛型也是一个考虑的因素。