proxyBeanMethods = false

@Configuration(proxyBeanMethods = false)
@ConditionalOnProperty(prefix = "spring.mail", name = "host")
class MailSenderPropertiesConfiguration {

   @Bean
   @ConditionalOnMissingBean(JavaMailSender.class)
   JavaMailSenderImpl mailSender(MailProperties properties) {
      JavaMailSenderImpl sender = new JavaMailSenderImpl();
      applyProperties(properties, sender);
      return sender;
   }
proxyBeanMethods = false不代理bean方法，每次獲取都是重新創建
反之，代理bean方法，代理干的事情：判斷這個bean對象是否存在，如果存在就直接在ioc中拿