Spring怎么使用注解进行引用类型的自动装(spring,开发技术)

一.案例分级

简单解析:配置类替代以前的配置文件，实体类提供对象，业务类中有实体类的引用对象，在业务层中实现引用类的自动装配。

二.各层代码及详细解析

配置类:(关于配置类中两个注解的解释可以参考前面文章)

packagecom.itheima.config;importorg.springframework.context.annotation.ComponentScan;importorg.springframework.context.annotation.Configuration;@Configuration//设置为配置类@ComponentScan("com.itheima")//在com.otheima这个包下扫描bean对象publicclassSpringConfig{}

实体类BookDaoImpl:

packagecom.itheima.dao.impl;importcom.itheima.dao.BookDao;importorg.springframework.context.annotation.Scope;importorg.springframework.stereotype.Component;importorg.springframework.stereotype.Repository;@Repository//注解注册beanpublicclassBookDaoImplimplementsBookDao{publicvoidsave(){System.out.println("bookdaosave...");}}

实体接口BookDao:

packagecom.itheima.dao;publicinterfaceBookDao{publicvoidsave();}

业务类BookServiceImol:

packagecom.itheima.service.impl;importcom.itheima.dao.BookDao;importcom.itheima.service.BookService;importorg.springframework.beans.factory.annotation.Autowired;importorg.springframework.stereotype.Service;@ServicepublicclassBookServiceImolimplementsBookService{@AutowiredprivateBookDaobookDao;publicvoidsave(){System.out.println("bookservicesave....");bookDao.save();}}

@Service:注册bean对象，在执行类中使用getBean()方法获取.

@Autowired:进行自动装配，如果没有此句话，将会出现以下错误运行结果:

业务接口BookService:

packagecom.itheima.service;publicinterfaceBookService{publicvoidsave();}

执行类App3:

packagecom.itheima;importcom.itheima.config.SpringConfig;importcom.itheima.dao.BookDao;importcom.itheima.service.BookService;importorg.springframework.context.annotation.AnnotationConfigApplicationContext;importjava.awt.print.Book;publicclassApp3{publicstaticvoidmain(String[]args){AnnotationConfigApplicationContextctx=newAnnotationConfigApplicationContext(SpringConfig.class);BookServiceservice=ctx.getBean(BookService.class);service.save();}}

三.自动装配成功正确执行结果