SpringBooot 创建 Web 项目
异步任务：
service 包下创建 AsyncService 类
@Async 异步方法
Thread.sleep(3000) 停止三秒，捕获异常
package com.demo.task.service;import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;//异步
@Service
public class AsyncService {//异步方法@Asyncpublic void hello(){try {Thread.sleep(3000);} catch (InterruptedException e) {//throw new RuntimeException(e);e.printStackTrace();}System.out.println("数据正在处理");}
}
controller 包下创建 AsyncController 类
自动装配 AsyncService
方法里调用 AsyncService 类里的 hello 方法，停止三秒
package com.demo.task.controller;import com.demo.task.service.AsyncService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
public class AsyncController {@AutowiredAsyncService asyncService;@RequestMapping("/hello")public String hello(){asyncService.hello();return "OK";}
}主程序添加 @EnableAsync 开启异步注解功能
package com.demo.task;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;@EnableAsync //开启异步注解功能
@SpringBootApplication
public class TaskApplication {public static void main(String[] args) {SpringApplication.run(TaskApplication.class, args);}
}启动即可，记得地址加后缀
（加了注解后，实际上响应很快，页面很快出现，但程序执行过了三秒，就是输出的那句“数据正在处理”过了三秒出现）
邮件任务：
pom.xml 导入 spring-boot-starter-mail 的 jar 包
<!-- 导入javax.mail --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-mail</artifactId></dependency>拿 qq 邮箱举例，点击设置 -> 账号，下滑找到 POP3/IMAP/SMTP/Exchange/CardDAV/CalDAV 服务
点击管理服务，获取到授权码
application.properties 配置邮箱信息：
#邮箱账号
spring.mail.username=xx@qq.com
#邮箱密码：授权码
spring.mail.password=xx
spring.mail.host=smtp.qq.com
#开启加密验证
spring.mail.properties.mail.smtp.ssl.enable=true测试类：
自动装配 JavaMailSenderImpl
new 一个 SimpleMailMessage，调用邮件相关信息
最后发送即可
package com.demo.task;import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSenderImpl;@SpringBootTest
class TaskApplicationTests {@AutowiredJavaMailSenderImpl mailSender;@Testvoid contextLoads() {SimpleMailMessage message = new SimpleMailMessage();message.setSubject("邮件主题");message.setText("文本内容");message.setTo("xx@qq.com");message.setFrom("xx@qq.com");mailSender.send(message);}}上述只是简单的邮件，复杂邮件如下：
createMimeMessage -> new MimeMessageHelper -> ... -> send
package com.demo.task;import jakarta.mail.MessagingException;
import jakarta.mail.internet.MimeMessage;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.mail.javamail.JavaMailSenderImpl;
import org.springframework.mail.javamail.MimeMessageHelper;import java.io.File;@SpringBootTest
class TaskApplicationTests {@AutowiredJavaMailSenderImpl mailSender;@Testvoid contextLoads2() throws MessagingException {MimeMessage mimeMessage = mailSender.createMimeMessage();//组装MimeMessageHelper helper = new MimeMessageHelper(mimeMessage,true,"utf-8");helper.setSubject("邮件主题");helper.setText("<p style='color:red'>文本内容</p>",true);//附件helper.addAttachment("1.jpg",new File("E:\\1.jpg"));helper.setTo("xx@qq.com");helper.setFrom("xx@qq.com");mailSender.send(mimeMessage);}}定时任务：
主程序类上添加一行 @EnableScheduling 开启定时功能
package com.demo.task;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;@EnableAsync //开启异步注解功能
@EnableScheduling //开启定时功能的注解
@SpringBootApplication
public class TaskApplication {public static void main(String[] args) {SpringApplication.run(TaskApplication.class, args);}
}
service 包下创建 ScheduledService 类：
方法上添加 @Scheduled 注解
package com.demo.task.service;import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Service;@Service
public class ScheduledService {//定时：在一个特定的时间执行程序//core表达式： 秒 分 时 日 月 周几// 0/2 14 13 ? * 1-5 每个月周一到周五13点14分，每隔两秒执行一次@Scheduled(cron = "0 20 5 * * ?") //每天5点20分0秒执行方法public void hello(){System.out.println("hello");}
}
查看 Scheduled 源码，提供了多种配置调度任务的方式
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repeatable(Schedules.class)
@Reflective
public @interface Scheduled {String CRON_DISABLED = "-";String cron() default "";String zone() default "";long fixedDelay() default -1L;String fixedDelayString() default "";long fixedRate() default -1L;String fixedRateString() default "";long initialDelay() default -1L;String initialDelayString() default "";TimeUnit timeUnit() default TimeUnit.MILLISECONDS;String scheduler() default "";
}Cron 在线表达式生成器
可以实现在线生成表达式