Bean 初始化的方式与顺序

￡神魔★判官ぃ 2022-10-31 13:54 195阅读 0赞

Bean 在实例化完成后，可以配置初始化，方式如下：

*  @PostConstruct 注解作用于方法
 *  实现 InitializingBean 接口，复写 afterPropertiesSet 方法
 *  自定义 initMethod：xml <bean init-method="init">属性、@Bean(initMethod = "init")、BeanDefinitionBuilder\#setInitMethodName

示例代码：

spring 配置文件

<?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">
    
        <bean id="user1" class="constxiong.User" init-method="init">
            <property name="source" value="xml"/>
        </bean>
    
        
        <context:component-scan base-package="constxiong"/>
    
    </beans>

User 类

package constxiong;
    
    import org.springframework.beans.factory.InitializingBean;
    
    import javax.annotation.PostConstruct;
    
    public class User implements InitializingBean {
    
    	private String source;
    
    	private Integer id;
    	
    	private String name;
    	
    	public User() {
    	}
    
    	@PostConstruct
    	public void postConstruct() {
    		this.id = 1;
    		this.name = "cx1";
    		System.out.println(this);
    		System.out.println(source + ": User#postConstruct executed
    ");
    	}
    
    	@Override
    	public void afterPropertiesSet() throws Exception {
    		this.id = 2;
    		this.name = "cx2";
    		System.out.println(this);
    		System.out.println(source + ": User#afterPropertiesSet executed
    ");
    	}
    
    	public void init() {
    		this.id = 3;
    		this.name = "cx3";
    		System.out.println(this);
    		System.out.println(source + ": User#init executed
    ");
    	}
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public String getSource() {
    		return source;
    	}
    
    	public void setSource(String source) {
    		this.source = source;
    	}
    
    	@Override
    	public String toString() {
    		return "User{" +
    				"source='" + source + ''' +
    				", id=" + id +
    				", name='" + name + ''' +
    				'}';
    	}
    }

测试代码

package constxiong;
    
    
    import org.springframework.beans.factory.support.BeanDefinitionBuilder;
    import org.springframework.beans.factory.support.DefaultListableBeanFactory;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /**
     * 测试 Bean 的初始化
     * @author ConstXiong
     */
    @Configuration
    public class Test {
    	
    	public static void main(String[] args) {
    		// xml init
    		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("META-INF/spring-bean-initialization.xml");
    		User user1 = context.getBean("user1", User.class);
    		System.out.println(user1);
    
    		// @Bean
    		User user2 = context.getBean("user2", User.class);
    		System.out.println(user2);
    
    		//BeanDefinition
    		((DefaultListableBeanFactory)context.getBeanFactory()).registerBeanDefinition("user3",
    				BeanDefinitionBuilder.rootBeanDefinition(User.class).setInitMethodName("init").addPropertyValue("source", "BeanDefinition").getBeanDefinition());
    		User user3 = context.getBean("user3", User.class);
    		System.out.println(user3);
    	}
    
    	@Bean(initMethod = "init", name = "user2")
    	public User getUser() {
    		User user = new User();
    		user.setSource("@Bean");
    		return user;
    	}
    
    }

打印结果

User{source='xml', id=1, name='cx1'}
    xml: User#postConstruct executed
    
    User{source='xml', id=2, name='cx2'}
    xml: User#afterPropertiesSet executed
    
    User{source='xml', id=3, name='cx3'}
    xml: User#init executed
    
    User{source='@Bean', id=1, name='cx1'}
    @Bean: User#postConstruct executed
    
    User{source='@Bean', id=2, name='cx2'}
    @Bean: User#afterPropertiesSet executed
    
    User{source='@Bean', id=3, name='cx3'}
    @Bean: User#init executed
    
    User{source='xml', id=3, name='cx3'}
    User{source='@Bean', id=3, name='cx3'}
    User{source='BeanDefinition', id=1, name='cx1'}
    BeanDefinition: User#postConstruct executed
    
    User{source='BeanDefinition', id=2, name='cx2'}
    BeanDefinition: User#afterPropertiesSet executed
    
    User{source='BeanDefinition', id=3, name='cx3'}
    BeanDefinition: User#init executed
    
    User{source='BeanDefinition', id=3, name='cx3'}

打印顺序：@PostConstruct -> InitializingBean \#afterPropertiesSet -> initMethd

[完整代码：008-spring-bean-intitialization][008-spring-bean-intitialization]

--------------------

### 【Java学习资源】整理推荐 ###

*  [Bean 的作用域][Bean]
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 *  [Spring 依赖注入与依赖查找来源的区别][Spring]
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 *  [ObjectFactory 与 BeanFactory 的区别][ObjectFactory _ BeanFactory]
 *  [Bean 销毁的方式与顺序][Bean 1]
 *  [Bean 初始化的方式与顺序][Bean 2]
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 *  [什么是 BeanDefinition？][BeanDefinition]
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 *  [BeanFactory 与 FactoryBean 的区别][BeanFactory _ FactoryBean]
 *  [BeanFactory 与 ApplicationContext 的区别][BeanFactory _ ApplicationContext]
 *  [Spring IoC 依赖注入的实现方式][Spring IoC 1]
 *  [Spring IoC 依赖注入(支持哪些数据类型？)][Spring IoC 2]
 *  [Spring bean 依赖查找][Spring bean]
 *  [Spring-IoC][]
 *  [Spring 的核心特性][Spring 1]

--------------------

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*  [基础与语法][Link 1]
 *  [集合][Link 2]
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 *  [Web][]
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 *  [框架][Link 7]
 *  [算法与数据结构][Link 8]
 *  [异常][Link 9]
 *  [文件解析与生成][Link 10]
 *  [Linux][]
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[008-spring-bean-intitialization]: https://github.com/ConstXiong/toy/tree/master/spring-study/008-spring-bean-intitialization
[Bean]: https://www.javanav.com/val/59101a7207864f4aa971e5c48b592c77.html
[maven _ tomcat _ jar _ web]: https://www.javanav.com/val/b1f4691bd6ba488a80e3bdfcefdec33c.html
[Spring]: https://www.javanav.com/val/a9569837e1bc4df9aeac0e6cbf96bf06.html
[Spring _ DependencyDescriptor]: https://www.javanav.com/val/152161d266a94fd38efb365a78d8f9a3.html
[Spring _ Aware]: https://www.javanav.com/val/089b3993c8bc4dec891ea677c104c5e4.html
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[ObjectFactory _ BeanFactory]: https://www.javanav.com/val/016d62d99b0148feaf13529a841f4e46.html
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[BeanDefinition]: https://www.javanav.com/val/e82279480ec24184bcaf723a50ef08b3.html
[Spring IoC]: https://www.javanav.com/val/d382c8380fc2480788a35a7e671b5e9b.html
[BeanFactory _ FactoryBean]: https://www.javanav.com/val/173e873a2c98499a8a08a13b4f88ae10.html
[BeanFactory _ ApplicationContext]: https://www.javanav.com/val/bbc2c9580b7045e583855925d5f1a50b.html
[Spring IoC 1]: https://www.javanav.com/val/a835e6c709ea439ebb21a80f1bf77926.html
[Spring IoC 2]: https://www.javanav.com/val/e377beac22644c2c85308079b239a0fd.html
[Spring bean]: https://www.javanav.com/val/7f8c2e1f24db46e79bc4b9b04f9ad715.html
[Spring-IoC]: https://www.javanav.com/val/a412668efda74412a13f6df9a6d2c714.html
[Spring 1]: https://www.javanav.com/val/6eac12a548ea40c68ff64b1af307563a.html
[Link 1]: https://www.javanav.com/interview/93b0069472fd479393006c0e73043fc4.html
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[Link 10]: https://www.javanav.com/interview/67a50996c28f418e83b109ea42fc3eff.html
[Linux]: https://www.javanav.com/interview/00cccb81729540d1923bd0a0ef49533a.html
[MySQL]: https://www.javanav.com/interview/d311e78502a845f1a4bb307bd6aec2b3.html
[Oracle]: https://www.javanav.com/interview/5f29e9677edf4a16be3dce30d257c9ab.html
[Redis]: https://www.javanav.com/interview/066c62b3af4d4827b2243a822c3084a9.html
[Dubbo]: https://www.javanav.com/interview/9a3e7a7740324757abaab953f7ebc455.html