bean的加载过程
目录
1.加载过程
2.示例：
3.注意：
1.加载过程
①Bean 实例化
通过构造函数或工厂方法创建 Bean 的实例
②手动设置属性
通过set方法进行赋值
③属性注入
Spring 容器将配置的属性值注入到 Bean 中（通过 @Autowired、@Value、@NacosValue 等注解或 XML 配置）。
④初始化
先调用调用 @PostConstruct 方法，再调用InitializingBean 的 afterPropertiesSet 方法，再调用自定义的初始化方法（通过 initMethod 指定）
⑤bean加载完成可以使用
⑥容器关闭时进行销毁
先调用 @PreDestroy 方法，再调用 DisposableBean 的 destroy 方法。然后调用自定义的销毁方法（通过 destroyMethod 指定）
2.示例：
配置bean
package com.example.demo6.service;
import lombok.Data;
import org.checkerframework.checker.units.qual.C;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
@Data
public class MyBean implements InitializingBean, DisposableBean {
private Integer id;
public MyBean() {
System.out.println("执行无参构造1");
}
static {
System.out.println("static1");
}
@Autowired
private MyBeans myBeans;
@PostConstruct
public void postConstruct() {
System.out.println("postConstruct1");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("afterPropertiesSet1");
}
public void init() {
System.out.println("init1");
}
@Override
public void destroy() throws Exception {
System.out.println("afterPropertiesSet对应的销毁1");
}
@PreDestroy
public void preDestroy() {
System.out.println("postConstruct对应的销毁1");
}
public void destroyMethod() {
System.out.println("init对应的销毁1");
}
}
package com.example.demo6.service;
import lombok.Data;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import java.io.Serializable;
@Data
public class MyBeans implements InitializingBean, DisposableBean {
private Integer id;
public MyBeans() {
System.out.println("执行无参构造2");
}
static {
System.out.println("static2");
}
@PostConstruct
public void postConstruct() {
System.out.println("postConstruct2");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("afterPropertiesSet2");
}
public void init() {
System.out.println("init2");
}
@Override
public void destroy() throws Exception {
System.out.println("afterPropertiesSet对应的销毁2");
}
@PreDestroy
public void preDestroy() {
System.out.println("postConstruct对应的销毁2");
}
public void destroyMethod() {
System.out.println("init对应的销毁2");
}
}
package com.example.demo6.config;
import com.example.demo6.service.MyBean;
import com.example.demo6.service.MyBeans;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class TestConfig {
@Bean(initMethod="init",destroyMethod="destroyMethod")
public MyBean myBean(){
MyBean myBean = new MyBean();
myBean.setId(1);
System.out.println("属性赋值1");
return myBean;
}
@Bean(initMethod="init",destroyMethod="destroyMethod")
public MyBeans myBeans() {
System.out.println("属性赋值2");
return new MyBeans();
}
}
启动容器
import com.example.demo6.config.TestConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Test {
public static void main(String[] args) {
System.out.println("容器启动");
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(TestConfig.class);
System.out.println("加载完成");
System.out.println("bean使用");
context.close();
}
}
执行结果：
容器启动
22:21:50.639 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@5474c6c
22:21:50.649 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
22:21:50.789 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
22:21:50.790 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
22:21:50.790 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
22:21:50.794 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
22:21:50.810 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'testConfig'
22:21:50.816 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'myBean'
static1
执行无参构造1
属性赋值1
22:21:50.839 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'myBeans'
static2
执行无参构造2
属性赋值2
postConstruct2
afterPropertiesSet2
init2
postConstruct1
afterPropertiesSet1
init1
加载完成
bean使用
22:21:50.859 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@5474c6c, started on Wed Mar 12 22:21:50 CST 2025
postConstruct对应的销毁1
afterPropertiesSet对应的销毁1
init对应的销毁1
postConstruct对应的销毁2
afterPropertiesSet对应的销毁2
init对应的销毁23.注意：
①静态代码块最先执行
②如果父类实现了InitializingBean接口，子类会执行父类的afterPropertiesSet方法，场景的动态数据源的实现类AbstractRoutingDataSource
③类的生命周期
- 加载（Loading）阶段：将类的字节码载入内存
- 链接（Linking）阶段
- 验证（Verification）确保 Class 文件的字节流符合 JVM 规范
- 准备（Preparation）为类的静态变量分配内存并设置初始值
- 解析（Resolution）将常量池中的符号引用替换为直接引用
- 初始化（Initialization）阶段
- 静态变量赋值
- 静态代码执行
- 使用（Using）阶段
- 类的实例化
- 属性注入
- 初始化方法执行
- 使用bean
- 卸载（Unloading）阶段