Spring5学习03:IOC注解

蔚落 2022-10-21 11:54 140阅读 0赞

## 1.注解 ##

> 1.  注解是代码特殊标记，格式：@注解名称(属性名称=属性值, 属性名称=属性值…)
> 2.  使用注解，注解作用在类上面，方法上面，属性上面
> 3.  使用注解目的：简化 xml 配置

## 2.常用注解 ##

>  *  @Component
>  *  @Service
>  *  @Controller
>  *  @Repository

上面四个注解功能是一样的，都可以用来创建 bean 实例

## 3.对象创建 ##

1.xml配置扫描

<?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.xsd">
    
    
        <context:component-scan  base-package= "cn.zj"></context:component-scan>
    
    </beans>
    package cn.zj.service;
    
    import org.springframework.stereotype.Service;
    
    //在注解里面 value 属性值可以省略不写，
    //默认值是类名称，首字母小写
    //UserService -- userService
    @Service(value = "userService")
    public class UserService {
        public void add() {
            System.out.println("service add.......");
        }
    }

测试

@Test
        public void test1() {
            ApplicationContext context = new ClassPathXmlApplicationContext("bean1.xml");
            // 2 获取配置创建的对象
            UserService userService = context.getBean("userService", UserService.class);
            userService.add();
        }

打印

service add.......

## 4.开启组件扫描细节配置 ##

<context:component-scan
            base-package="com.atguigu" use-default-filters="false">
            <context:include-filter type="annotation"
                expression="org.springframework.stereotype.Controller" />
        </context:component-scan>
        
        <context:component-scan base-package="com.atguigu">
            <context:exclude-filter type="annotation"
                expression="org.springframework.stereotype.Controller" />
        </context:component-scan>

## 5.属性注入 ##

### 1.@Autowired：根据属性类型进行自动装配 ###

@Repository
    public class UserDaoImpl implements UserDao {
    
        @Override
        public void add() {
            System.out.println("userDao add...");
    
        }
    
    }
    
    @Service(value = "userService")
    public class UserService {
        
        @Autowired
        private UserDao userDao;
        
        public void add() {
            System.out.println("service add.......");
            userDao.add();
        }
    }

### 2.@Qualifier：根据名称进行注入 ###

需要和@Autowired 一起使用

@Repository(value="userDaoImpl01")
    public class UserDaoImpl implements UserDao {
    
    }
    
    
       @Autowired
        @Qualifier(value="userDaoImpl01")
        private UserDao userDao;

### 3.@Resource：可以根据类型注入，可以根据名称注入 ###

//根据类型注入    
        @Resource
        private UserDao userDao;
    
        //根据名称注入  
        @Resource(name="userDaoImpl01")
        private UserDao userDao;

### 4.@Value：注入普通类型属性 ###

@Value("张三")
        private String name;

## 6.完全注解开发(工作中一般是用springboot方式开发) ##

1.创建配置配

//配置类,替代xml文件
    @Configuration  
    @ComponentScan(basePackages = "cn.zj")
    public class SpringConfig {
    
    }

2.测试类

@Test
        public void test2() {
            
            ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
            UserService userService = context.getBean("userService", UserService.class);
            userService.add();
        }