Bean指定初始化和销毁方法
经常用在数据源初始化时给参数赋值,销毁时关闭连接
指定初始化和销毁方法有两种,一种是通过@Bean指定init-method和destroy-method;
还有一种是通过让Bean实现InitializingBean定义初始化逻辑,实现DisposableBean定义销毁逻辑
注意
DisposableBean和destroy-method不能共用,init-method和InitializingBean可以共用,先执行afterPropertiesSet,再执行init方法
演示:
Bean
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package com.eh.bean;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
@Slf4j
@Data
public class Person {
private String name;
private Integer age;
public Person() {
log.info("=====>执行构造方法");
}
public void init() {
log.info("=====>初始化...");
}
public void destroy() {
log.info("=====>销毁...");
}
}
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定义init和destroy
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package com.eh.config;
import com.eh.bean.Person;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MainConfig {
/**
* bean的生命周期:
* bean创建---初始化----销毁的过程
* 容器管理bean的生命周期;
* 我们可以自定义初始化和销毁方法;容器在bean进行到当前生命周期的时候来调用我们自定义的初始化和销毁方法
* <p>
* 构造(对象创建)
* 单实例:在容器启动的时候创建对象
* 多实例:在每次获取的时候创建对象
* <p>
* 初始化:
* 对象创建完成,并赋值好,调用初始化方法。。。
* <p>
* 销毁:
* 单实例:容器关闭的时候
* 多实例:容器只负责创建对象但不会管理这个bean,所以容器不会调用销毁方法;
*
*/
@Bean(initMethod = "init", destroyMethod = "destroy")
public Person person() {
return new Person();
}
}
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测试:
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public static void main(String[] args) {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
applicationContext.close();
}
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输出
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23:48:24.864 [main] INFO com.eh.bean.Person.<init>(Person.java:13) - =====>执行构造方法
23:48:24.874 [main] INFO com.eh.bean.Person.init(Person.java:17) - =====>初始化...
23:48:24.917 [main] INFO com.eh.bean.Person.destroy(Person.java:21) - =====>销毁...
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InitializingBean和DisposableBean
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package com.eh.bean;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
@Slf4j
@Data
public class Person implements InitializingBean, DisposableBean {
private String name;
private Integer age;
public Person() {
log.info("=====>执行构造方法");
}
public void init() {
log.info("=====>初始化...");
}
public void destroy() {
log.info("=====>销毁...");
}
@Override
public void afterPropertiesSet() throws Exception {
log.info("=====>afterPropertiesSet");
}
}
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@Bean(initMethod = "init")
public Person person() {
return new Person();
}
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测试结果:
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00:05:52.570 [main] INFO com.eh.bean.Person.<init>(Person.java:15) - =====>执行构造方法
00:05:52.571 [main] INFO com.eh.bean.Person.afterPropertiesSet(Person.java:28) - =====>afterPropertiesSet
00:05:52.572 [main] INFO com.eh.bean.Person.init(Person.java:19) - =====>初始化...
00:05:52.591 [main] INFO com.eh.bean.Person.destroy(Person.java:23) - =====>销毁...
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@PostConstruct和@PreDestroy
这两个注解是JSR250定义的
测试:
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package com.eh.bean;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
@Slf4j
@Data
public class Person implements InitializingBean, DisposableBean {
private String name;
private Integer age;
public Person() {
log.info("=====>执行构造方法");
}
//对象创建并赋值之后调用
@PostConstruct
public void postConstruct() {
log.info("=====>postConstruct...");
}
//容器移除对象之前
@PreDestroy
public void preDestroy() {
log.info("=====>preDestroy...");
}
public void init() {
log.info("=====>init...");
}
public void destroy() {
log.info("=====>destroy...");
}
@Override
public void afterPropertiesSet() throws Exception {
log.info("=====>afterPropertiesSet");
}
}
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执行结果:
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00:10:58.851 [main] INFO com.eh.bean.Person.<init>(Person.java:18) - =====>执行构造方法
00:10:58.857 [main] INFO com.eh.bean.Person.postConstruct(Person.java:23) - =====>postConstruct...
00:10:58.858 [main] INFO com.eh.bean.Person.afterPropertiesSet(Person.java:41) - =====>afterPropertiesSet
00:10:58.858 [main] INFO com.eh.bean.Person.init(Person.java:32) - =====>init...
00:10:58.906 [main] INFO com.eh.bean.Person.preDestroy(Person.java:28) - =====>preDestroy...
00:10:58.906 [main] INFO com.eh.bean.Person.destroy(Person.java:36) - =====>destroy...
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BeanPostProcessor
后置处理器
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package com.eh.bean;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;
/**
* 后置处理器:初始化前后进行处理工作
* 将后置处理器加入到容器中
*/
@Slf4j
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
log.info("postProcessBeforeInitialization..." + beanName);
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("postProcessAfterInitialization..." + beanName);
return bean;
}
}
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测试结果:
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00:28:36.360 - =====>执行构造方法
00:28:36.363 - postProcessBeforeInitialization...person
00:28:36.363 - =====>postConstruct...
00:28:36.363 - =====>afterPropertiesSet
00:28:36.364 - =====>init...
postProcessAfterInitialization...person
00:28:36.395 - =====>preDestroy...
00:28:36.395 - =====>destroy...
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可以看到postProcessBeforeInitialization和postProcessAfterInitialization分别在初始化最前和最后执行
源码分析
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跟到org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
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// 给Bean属性赋值,各种set方法,这里也有后置处理器在工作,后面再讲
populateBean(beanName, mbd, instanceWrapper);
// 初始化Bean(调用各种初始化方法)
exposedObject = initializeBean(beanName, exposedObject, mbd);
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-
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean(java.lang.String, java.lang.Object, org.springframework.beans.factory.support.RootBeanDefinition)
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Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
// 先执行postProcessBeforeInitialization方法,在InitDestroyAnnotationBeanPostProcessor这个后置处理器执行postConstruct方法
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// 执行init、postProcessAfterInitialization方法
invokeInitMethods(beanName, wrappedBean, mbd);
}
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-
applyBeanPostProcessorsBeforeInitialization
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public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
// 获取容器中所有的BeanPostProcessor;挨个执行beforeInitialization,一但返回null,跳出for循环,不会执行后面的BeanPostProcessor.postProcessorsBeforeInitialization
for (BeanPostProcessor processor : getBeanPostProcessors()) {
Object current = processor.postProcessBeforeInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
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-
invokeInitMethods
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protected void invokeInitMethods(String beanName, Object bean, @Nullable RootBeanDefinition mbd)
throws Throwable {
// 执行InitializingBean初始化方法
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isTraceEnabled()) {
logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
((InitializingBean) bean).afterPropertiesSet();
return null;
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
((InitializingBean) bean).afterPropertiesSet();
}
}
// 执行init方法
if (mbd != null && bean.getClass() != NullBean.class) {
String initMethodName = mbd.getInitMethodName();
if (StringUtils.hasLength(initMethodName) &&
!(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
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BeanPostProcessor在spring底层的使用

ApplicationContextAwareProcessor
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class ApplicationContextAwareProcessor implements BeanPostProcessor {
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org.springframework.context.support.ApplicationContextAwareProcessor#invokeAwareInterfaces
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private void invokeAwareInterfaces(Object bean) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
if (bean instanceof ApplicationContextAware) {
// 这里进行方法回调,所以我们的Bean实现ApplicationContextAware就能将容器注入进来
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
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BeanValidationPostProcessor
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public class BeanValidationPostProcessor implements BeanPostProcessor, InitializingBean {
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@Override
public void afterPropertiesSet() {
if (this.validator == null) {
this.validator = Validation.buildDefaultValidatorFactory().getValidator();
}
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!this.afterInitialization) {
// 校验工作
doValidate(bean);
}
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (this.afterInitialization) {
// 校验工作
doValidate(bean);
}
return bean;
}
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InitDestroyAnnotationBeanPostProcessor
调用@PostConstruct和@PreDestroy注解的方法
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public void invokeInitMethods(Object target, String beanName) throws Throwable {
Collection<LifecycleElement> checkedInitMethods = this.checkedInitMethods;
Collection<LifecycleElement> initMethodsToIterate =
(checkedInitMethods != null ? checkedInitMethods : this.initMethods);
if (!initMethodsToIterate.isEmpty()) {
for (LifecycleElement element : initMethodsToIterate) {
if (logger.isTraceEnabled()) {
logger.trace("Invoking init method on bean '" + beanName + "': " + element.getMethod());
}
element.invoke(target);
}
}
}
public void invokeDestroyMethods(Object target, String beanName) throws Throwable {
Collection<LifecycleElement> checkedDestroyMethods = this.checkedDestroyMethods;
Collection<LifecycleElement> destroyMethodsToUse =
(checkedDestroyMethods != null ? checkedDestroyMethods : this.destroyMethods);
if (!destroyMethodsToUse.isEmpty()) {
for (LifecycleElement element : destroyMethodsToUse) {
if (logger.isTraceEnabled()) {
logger.trace("Invoking destroy method on bean '" + beanName + "': " + element.getMethod());
}
element.invoke(target);
}
}
}
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AutowiredAnnotationBeanPostProcessor
帮我们自动装配bean
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public class AutowiredAnnotationBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter
implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware {
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