spring —— IoC容器（二）
二、基于注解管理 bean（一）Autowired 主动装配
（1）属性上主动装配
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 {
@Autowired
private 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/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<context:component-scan base-package="com.fourth.anno"></context:component-scan>
</beans> （2）set 方法上主动装配
package com.fourth.anno;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class Service {
private Dao dao;
@Autowired
public void setDao(Dao dao){
this.dao=dao;
}
public void runService(){
dao.runDao();
}
} （3）构造方法上主动装配
package com.fourth.anno;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class Service {
private Dao dao;
@Autowired
public Service(Dao dao) {
this.dao = dao;
}
public void runService(){
dao.runDao();
}
} （4）构造方法的形参上主动装配
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 主动装配
（1）属性上主动装配
package com.fourth.anno;
import jakarta.annotation.Resource;
import org.springframework.stereotype.Component;
@Component
public class Service {
@Resource
private Dao dao;
public void runService(){
dao.runDao();
}
} （2）set 方法上主动装配
package com.fourth.anno;
import jakarta.annotation.Resource;
import org.springframework.stereotype.Component;
@Component
public class Service {
private Dao dao;
@Resource
public 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；其默认通过范例进行装配。
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，假如 JDK 版本高于11或低于8，应引入以下依赖：
<strong><dependency>
<groupId>jakarta.annotation</groupId>
<artifactId>jakarta.annotation-api</artifactId>
<version>2.1.1</version>
</dependency></strong> （三）全注解开发
全注解开发，纵然用配置类代替 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;
@Resource
public 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();
}
}
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