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 {
@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;
@Autowired
public 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;
@Autowired
public 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 {
@Resource
private 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;
@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;
@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();
}
}