Spring Bean生命周期全面解析
目录
概述
Spring Bean生命周期阶段
1. 实例化阶段
2. 属性赋值阶段
3. Aware接口回调阶段
4. BeanPostProcessor前置处理
5. 初始化阶段
@PostConstruct注解方法
InitializingBean接口
自定义init方法
6. BeanPostProcessor后置处理
7. Bean使用阶段
8. 销毁阶段
@PreDestroy注解方法
DisposableBean接口
自定义destroy方法
完整示例代码
1. 定义Bean类
2. 配置BeanPostProcessor
3. 配置类
4. 测试类
生命周期流程图
总结
概述
Spring Bean的生命周期是Spring框架的核心概念之一，理解Bean从创建到销毁的整个过程对于开发高质量的Spring应用程序至关重要。本文将详细梳理Spring Bean生命周期的各个阶段，并通过代码示例展示每个关键节点。
Spring Bean生命周期阶段
1. 实例化阶段
Spring容器通过构造函数或工厂方法创建Bean实例
public class ExampleBean {public ExampleBean() {System.out.println("1. Bean实例化 - 构造函数执行");}
}2. 属性赋值阶段
Spring容器注入Bean的属性和依赖
public class ExampleBean {private String name;private AnotherBean anotherBean;// Setter方法用于属性注入public void setName(String name) {System.out.println("2. 属性注入 - name: " + name);this.name = name;}public void setAnotherBean(AnotherBean anotherBean) {System.out.println("2. 依赖注入 - anotherBean");this.anotherBean = anotherBean;}
}3. Aware接口回调阶段
Bean实现Aware接口获取容器资源
public class ExampleBean implements BeanNameAware, BeanFactoryAware, ApplicationContextAware {@Overridepublic void setBeanName(String name) {System.out.println("3. BeanNameAware - Bean名称: " + name);}@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {System.out.println("3. BeanFactoryAware - BeanFactory注入");}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {System.out.println("3. ApplicationContextAware - ApplicationContext注入");}
}4. BeanPostProcessor前置处理
BeanPostProcessor的postProcessBeforeInitialization方法
@Component
public class CustomBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {if (bean instanceof ExampleBean) {System.out.println("4. BeanPostProcessor前置处理 - " + beanName);}return bean;}
}5. 初始化阶段
@PostConstruct注解方法
public class ExampleBean {@PostConstructpublic void postConstruct() {System.out.println("5.1 @PostConstruct方法执行");}
}InitializingBean接口
public class ExampleBean implements InitializingBean {@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("5.2 InitializingBean.afterPropertiesSet()执行");}
}自定义init方法
public class ExampleBean {public void customInit() {System.out.println("5.3 自定义init方法执行");}
}// 配置类中指定init方法
@Configuration
public class AppConfig {@Bean(initMethod = "customInit")public ExampleBean exampleBean() {return new ExampleBean();}
}6. BeanPostProcessor后置处理
BeanPostProcessor的postProcessAfterInitialization方法
@Component
public class CustomBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {if (bean instanceof ExampleBean) {System.out.println("6. BeanPostProcessor后置处理 - " + beanName);}return bean;}
}7. Bean使用阶段
Bean完全初始化，可供应用程序使用
@Service
public class BusinessService {private final ExampleBean exampleBean;public BusinessService(ExampleBean exampleBean) {this.exampleBean = exampleBean;}public void doBusiness() {System.out.println("7. Bean使用阶段 - 执行业务逻辑");}
}8. 销毁阶段
@PreDestroy注解方法
public class ExampleBean {@PreDestroypublic void preDestroy() {System.out.println("8.1 @PreDestroy方法执行");}
}DisposableBean接口
public class ExampleBean implements DisposableBean {@Overridepublic void destroy() throws Exception {System.out.println("8.2 DisposableBean.destroy()执行");}
}自定义destroy方法
public class ExampleBean {public void customDestroy() {System.out.println("8.3 自定义destroy方法执行");}
}// 配置类中指定destroy方法
@Configuration
public class AppConfig {@Bean(destroyMethod = "customDestroy")public ExampleBean exampleBean() {return new ExampleBean();}
}完整示例代码
1. 定义Bean类
import org.springframework.beans.factory.*;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;public class LifecycleBean implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean, DisposableBean {private String name;private AnotherBean anotherBean;public LifecycleBean() {System.out.println("1. 构造函数执行 - Bean实例化");}public void setName(String name) {System.out.println("2. 属性注入 - name: " + name);this.name = name;}public void setAnotherBean(AnotherBean anotherBean) {System.out.println("2. 依赖注入 - anotherBean");this.anotherBean = anotherBean;}@Overridepublic void setBeanName(String name) {System.out.println("3. BeanNameAware - Bean名称: " + name);}@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {System.out.println("3. BeanFactoryAware - BeanFactory注入");}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {System.out.println("3. ApplicationContextAware - ApplicationContext注入");}@PostConstructpublic void postConstruct() {System.out.println("5.1 @PostConstruct方法执行");}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("5.2 InitializingBean.afterPropertiesSet()执行");}public void customInit() {System.out.println("5.3 自定义init方法执行");}public void doSomething() {System.out.println("7. Bean使用阶段 - 执行业务方法");}@PreDestroypublic void preDestroy() {System.out.println("8.1 @PreDestroy方法执行");}@Overridepublic void destroy() throws Exception {System.out.println("8.2 DisposableBean.destroy()执行");}public void customDestroy() {System.out.println("8.3 自定义destroy方法执行");}
}2. 配置BeanPostProcessor
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;@Component
public class CustomBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {if (bean instanceof LifecycleBean) {System.out.println("4. BeanPostProcessor前置处理 - " + beanName);}return bean;}@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {if (bean instanceof LifecycleBean) {System.out.println("6. BeanPostProcessor后置处理 - " + beanName);}return bean;}
}3. 配置类
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
public class AppConfig {@Bean(initMethod = "customInit", destroyMethod = "customDestroy")public LifecycleBean lifecycleBean() {LifecycleBean bean = new LifecycleBean();bean.setName("示例Bean");return bean;}@Beanpublic AnotherBean anotherBean() {return new AnotherBean();}
}4. 测试类
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class LifecycleTest {public static void main(String[] args) {System.out.println("Spring容器启动...");AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);System.out.println("\n获取Bean并执行业务方法...");LifecycleBean bean = context.getBean(LifecycleBean.class);bean.doSomething();System.out.println("\nSpring容器关闭...");context.close();System.out.println("程序结束");}
}生命周期流程图
Bean生命周期完整流程：
1. 实例化 → 2. 属性赋值 → 3. Aware接口回调 → 4. BeanPostProcessor前置处理 →
5. 初始化(@PostConstruct → InitializingBean → 自定义init) → 6. BeanPostProcessor后置处理 →
7. Bean就绪可用 → 8. 销毁(@PreDestroy → DisposableBean → 自定义destroy)总结
Spring Bean的生命周期是一个复杂但有序的过程，理解每个阶段的执行顺序和用途对于：
- 调试和问题排查：能够快速定位Bean初始化相关的问题
- 扩展功能：通过BeanPostProcessor等机制扩展Spring功能
- 资源管理：正确管理数据库连接、线程池等资源
- 性能优化：合理使用各种初始化机制提升应用性能