二、基于注解管理 bean
（一）Autowired 自动装配
（1）属性上自动装配
package com.fourth.anno;import org.springframework.stereotype.Component;@Component
public class Dao {public void runDao(){System.out.println("hello world");}
}package com.fourth.anno;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;@Component
public class Service {@Autowiredprivate Dao dao;public void runService(){dao.runDao();}
}package com.fourth.anno;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class Test {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("bean-anno.xml");Service service = context.getBean(Service.class);service.runService();}
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:context="http://www.springframework.org/schema/context"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd"><context:component-scan base-package="com.fourth.anno"></context:component-scan>
</beans>（2）set 方法上自动装配
package com.fourth.anno;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;@Component
public class Service { private Dao dao;@Autowiredpublic void setDao(Dao dao){this.dao=dao;}public void runService(){dao.runDao();}
}（3）构造方法上自动装配
package com.fourth.anno;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;@Component
public class Service {private Dao dao;@Autowiredpublic Service(Dao dao) {this.dao = dao;}public void runService(){dao.runDao();}
}（4）构造方法的形参上自动装配
package com.fourth.anno;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;@Component
public class Service {private Dao dao;public Service(@Autowired Dao dao) {this.dao = dao;}public void runService(){dao.runDao();}
}（二）Resource 自动装配
（1）属性上自动装配
package com.fourth.anno;import jakarta.annotation.Resource;
import org.springframework.stereotype.Component;@Component
public class Service {@Resourceprivate Dao dao;public void runService(){dao.runDao();}
}（2）set 方法上自动装配
package com.fourth.anno;import jakarta.annotation.Resource;
import org.springframework.stereotype.Component;@Component
public class Service {private Dao dao;@Resourcepublic void setDao(Dao dao) {this.dao = dao;}public void runService(){dao.runDao();}
}Autowired 与 Resource 比较：
Autowired 可以应用在属性、set 方法、构造方法、构造方法的形参上；其默认通过类型进行装配。
Resource 可以应用在属性、set 方法上；其默认通过名称进行装配。
Autowired 基于 spring 框架；Resource 基于 java 扩展包，如果 JDK 版本高于11或低于8，应引入以下依赖：
<dependency><groupId>jakarta.annotation</groupId><artifactId>jakarta.annotation-api</artifactId><version>2.1.1</version>
</dependency>
（三）全注解开发
全注解开发，即使用配置类代替 xml 配置文件：
package com.fourth.anno;import org.springframework.stereotype.Component;@Component
public class Dao {public void runDao(){System.out.println("hello world");}
}package com.fourth.anno;import jakarta.annotation.Resource;
import org.springframework.stereotype.Component;@Component
public class Service {private Dao dao;@Resourcepublic void setDao(Dao dao) {this.dao = dao;}public void runService(){dao.runDao();}
}package com.fourth.anno;import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;@Configuration
@ComponentScan(value = "com.fourth.anno")
public class SpringConfig {
}package com.fourth.anno;import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class Test {public static void main(String[] args) {ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);Service service = context.getBean(Service.class);service.runService();}
}
