spring bean初始化扩展之InitializingBean和 init-method源码解析

InitializingBean和init-method介绍

InitializingBean

InitializingBean是一个接口，它定义了一个afterPropertiesSet方法

public interface InitializingBean {
   
   

	/**
	 * Invoked by the containing {@code BeanFactory} after it has set all bean properties
	 * and satisfied {@link BeanFactoryAware}, {@code ApplicationContextAware} etc.
	 * <p>This method allows the bean instance to perform validation of its overall
	 * configuration and final initialization when all bean properties have been set.
	 * @throws Exception in the event of misconfiguration (such as failure to set an
	 * essential property) or if initialization fails for any other reason
	 */
	void afterPropertiesSet() throws Exception;

}

init-method

init-method，一般我们在bean中会定义相关的初始化方法，希望spring容器初始bean时，调用我们定义的初始化方法，而这个方法我们一般会通过在xml配置bean时通过init-method标签来指定对应的初始化方法，或者是现在流行的注解式开发，通过@Bean(initMethod=“xxx”)指定对应的初始化方法。

@Configuration
public class MainConfigOfLifeCycle {
   
   
	@Bean(initMethod="init")
	public Car car(){
   
   
		return new Car();
	}
}

InitializingBean和init-method的作用执行时机

继续通过AbstractAutowireCapableBeanFactory中初始化bean的源码中，了解一下InitializingBean和init-method的作用执行时机。

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
   
   
		if (System.getSecurityManager() != null) {
   
   
			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
   
   
				invokeAwareMethods(beanName, bean);
				return null;
			}, getAccessControlContext());
		}
		else {
   
   
			//调用调用此方法进行部分Aware接口的回调
			invokeAwareMethods(beanName, bean);
		}

		Object wrappedBean