UserService.java

package com.itranswarp.learnjava.service;

import java.time.ZoneId;

import org.springframework.stereotype.Component;

@Component
public class UserService {

	public ZoneId zoneId = ZoneId.systemDefault();

	public UserService() {
		System.out.println("UserService(): init...");
		System.out.println("UserService(): zoneId = " + this.zoneId);
	}

	public ZoneId getZoneId() {
		return zoneId;
	}
}

MailService.java

public String sendMail() {
		// null:
		ZoneId zoneId = userService.getZoneId();
		String dt = ZonedDateTime.now(zoneId).toString();
		return "Hello, it is " + dt;
	}

运行结果：

13:43:49.819 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@10a035a0
13:43:49.831 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
13:43:49.869 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [D:\projects\study\java_pro\spring-aop-field\target\classes\com\itranswarp\learnjava\LoggingAspect.class]
13:43:49.869 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [D:\projects\study\java_pro\spring-aop-field\target\classes\com\itranswarp\learnjava\service\MailService.class]
13:43:49.870 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [D:\projects\study\java_pro\spring-aop-field\target\classes\com\itranswarp\learnjava\service\UserService.class]
13:43:49.930 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
13:43:49.931 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
13:43:49.932 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
13:43:49.933 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.aop.config.internalAutoProxyCreator'
13:43:50.007 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'appConfig'
13:43:50.023 [main] DEBUG org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory - Found AspectJ method: public void com.itranswarp.learnjava.LoggingAspect.doAccessCheck()
13:43:50.087 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'loggingAspect'
13:43:50.088 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'mailService'
13:43:50.094 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'userService'
UserService(): init...
UserService(): zoneId = Asia/Shanghai
[Before] do access check...
Hello, it is 2022-08-23T13:43:50.134103900+08:00[Asia/Shanghai]