import org.springframework.beans.factory.InitializingBean;
import javax.annotation.PostConstruct;

public class Foo implements InitializingBean {

    public void init(){
        System.out.println("执行了init生命周期的初始化回调");
    }

    @PostConstruct
    public void postConstruct(){
        System.out.println("执行了postConstruct生命周期的初始化回调");
    }

    @Override
    public void afterPropertiesSet() {
        System.out.println("执行了afterPropertiesSet生命周期的初始化回调");
    }
}

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class InitConfiguration {
    @Bean(initMethod = "init")
    public Foo getInitMethodBean() {
        return new Foo();
    }
}

执行了postConstruct生命周期的初始化回调
执行了afterPropertiesSet生命周期的初始化回调
执行了init生命周期的初始化回调

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
    if (System.getSecurityManager() != null) {
      AccessController.doPrivileged(new PrivilegedAction<Object>() {
        @Override
        public Object run() {
          invokeAwareMethods(beanName, bean);
          return null;
        }
      }, getAccessControlContext());
    }
    else {
      invokeAwareMethods(beanName, bean);
    }

    Object wrappedBean = bean;
    if (mbd == null || !mbd.isSynthetic()) {
      // 此处执行的是@PostConstruct注解的方法 InitDestroyAnnotationBeanPostProcessor#postProcessBeforeInitialization
      wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
    }

    try {
      // 执行的是afterPropertiesSet和init-method方法      
      invokeInitMethods(beanName, wrappedBean, mbd);
    }
    catch (Throwable ex) {
      throw new BeanCreationException(
          (mbd != null ? mbd.getResourceDescription() : null),
          beanName, "Invocation of init method failed", ex);
    }

    if (mbd == null || !mbd.isSynthetic()) {
      wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    }
    return wrappedBean;
  }

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
      throws Throwable {

    boolean isInitializingBean = (bean instanceof InitializingBean);
    if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
      if (logger.isDebugEnabled()) {
        logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
      }
      if (System.getSecurityManager() != null) {
        try {
          AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
            @Override
            public Object run() throws Exception {
              ((InitializingBean) bean).afterPropertiesSet();
              return null;
            }
          }, getAccessControlContext());
        }
        catch (PrivilegedActionException pae) {
          throw pae.getException();
        }
      }
      else {
        // 执行afterPropertiesSet方法
        ((InitializingBean) bean).afterPropertiesSet();
      }
    }

    if (mbd != null) {
      String initMethodName = mbd.getInitMethodName();
      if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
          !mbd.isExternallyManagedInitMethod(initMethodName)) {
        // 执行自定义的init-method方法
        invokeCustomInitMethod(beanName, bean, mbd);
      }
    }
  }