Task (asynchronous, scheduled, mail)

Asynchronous task~

• Multithreading

Timed task~

• timer
• Expression~

Mail sending~

• time
• pop3/SMTP service

1, Asynchronous task (async)

1. Application scenario

​ 1. It takes time to send e-mail. Open asynchrony to let the user receive the information of the sent e-mail first, and then another thread sends it successfully after the waiting time of sending e-mail

2. Cases

• Simulate a 3-second delay operation, and then delay the display of ok to the page. Now: to display ok, one thread will delay another thread by 3 seconds [if it is not added, the word ok will be loaded for 3 seconds before it comes out, affecting the user experience]

1. Write the simulation code first

   • service Under the bag AsyncService
     
     @Service
     public class AsyncService {
     
     
         public void delay(){
             try {
                 Thread.sleep(3000);
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }
     
             System.out.println("Data processing...");
         }
     }
     

   • controller Under the bag AsyncController
     
     @RestController
     public class AsyncController {
     
         @Autowired
         AsyncService asyncService;
     
         /*
         * What we need to achieve is that one thread directly outputs ok and the other thread does the operation with a delay of 3 seconds [does not affect the user experience]
         * */
         @RequestMapping("/delay")
         public String delay(){
             //Calling this method will delay 3 seconds,
             asyncService.delay();
             return "ok";
         }
     }
     

2. Tell Spring on the delay method that this is an asynchronous method

   • [@ Async notes]

   • With this annotation, as long as the program runs, it will open several thread pools for us

   • The asynchronous annotation function needs to be enabled in the main method

   • service Under the bag AsyncService
     
     @Service
     public class AsyncService {
     
     	//Tell Spring on the delay method that this is an asynchronous method
     	@Async
         public void delay(){
             try {
                 Thread.sleep(3000);
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }
     
             System.out.println("Data processing...");
         }
     }
     

3. Once this annotation is added, it is necessary to * * [enable asynchronous annotation function] in the main method**

   • [@ EnableAsync annotation]

   • //Enable asynchronous annotation
     @EnableAsync
     @SpringBootApplication
     public class Springboot09AsyncApplication {
     
         public static void main(String[] args) {
             SpringApplication.run(Springboot09AsyncApplication.class, args);
         }
     
     }
     

2, Mail sending

1. Configure jar package

2. Send with qq here

1. Find the account page of qq email and start the agreement service

1. A password is generated instead of its own plaintext password

3. Configure application yaml

spring:
  mail:
    username: 834399035@qq.com
    #Configured dynamic password
    password: kcsigtxaclybbfdj
    #Configure sending server
    host: smtp.qq.com
    # Set ssl on
    properties:
      mail:
        stmp:
          ssl:
            enable: true
         
    ##The following are turned on as appropriate
    # The default protocol is smtp
    #protocol: smtp
    #default-encoding: utf-8
    #port: 465
    # qq mailbox needs Turn on mailbox verification
    #properties.mail.smtp.ssl.enable=true
    #port: 587
    

4. Write the Test of sending e-mail in the Test test [write it in the Test first, and then write it in the controller or service]

@SpringBootTest
class Springboot09AsyncApplicationTests {

    @Autowired
    JavaMailSenderImpl javaMailSender;

    @Test
    void contextLoads() {

        //A simple email
        SimpleMailMessage mailMessage = new SimpleMailMessage();
        //title
        mailMessage.setSubject("Hello");
        //content
        mailMessage.setText("Your computer is suspected of stealing state secrets");
        mailMessage.setSentDate(new Date());
        //To whom
        mailMessage.setTo("496228526@qq.com");
        //From where
        mailMessage.setFrom("834399035@qq.com");

        javaMailSender.send(mailMessage);
    }

}

5. Write a complex email and send it [write it to Test first, and then write it to controller or service]

@Test
    void contextLoads2() throws MessagingException {

        //A complex mail sending
        MimeMessage mimeMessage = javaMailSender.createMimeMessage();
        //Assembly (you need to throw an exception here)
        MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true);

        //text
        helper.setSubject("Hello g1x");
        helper.setText("Send a complex email (with attachments)");

        //enclosure
        helper.addAttachment("2.jpg", new File("E:\\pictureOrFilms\\picture\\dota\\2.jpg"));
        helper.addAttachment("3.jpg", new File("E:\\pictureOrFilms\\picture\\dota\\3.jpg"));

        //send out
        helper.setFrom("834399035@qq.com");
        helper.setTo("834399035@qq.com");

        javaMailSender.send(mimeMessage);
    }

6. Write a tool class [that is, write a method]

    /**     *     * @param html  :The first parameter: whether to support multi text uploading, where true is changed to HTML * @ param subject: Title * @ param text: body * @ throws messagingexception * @ author G1x: see your needs by analogy later     */    public void sendMail(Boolean html, String subject, String text) throws MessagingException {        //Send a complex message mimemessage mimemessage = javamailsender createMimeMessage();        // Assembly (exceptions need to be thrown here) MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, html)// Text helper setSubject(subject);         helper. setText(text);        // Attachment helper addAttachment("2.jpg", new File("E:\pictureOrFilms\picture\dota\2.jpg"));         helper. addAttachment("3.jpg", new File("E:\pictureOrFilms\picture\dota\3.jpg"));        // Send helper setFrom(" 834399035@qq.com ");        helper.setTo(" 834399035@qq.com ");        javaMailSender.send(mimeMessage);    }

3, Timed task

*Two core interfaces

TaskScheduler	//Task scheduler TaskExecutor 	// Task executor

1. Notes to be added on the main operation method

@EnableScheduling	//Enable timed annotation function @ Scheduled 	// When to execute ------------------- / / enable asynchronous annotation@ EnableAsync@SpringBootApplication //Enable the timed annotation function @ enablesschedulingpublic class springboot09asyncapplication {public static void main (string [] args) {springapplication.run (springboot09asyncapplication. Class, args);}}

3. cron expression used in @ scheduled

• This cron expression can be generated online: https://cron.qqe2.com/

• There are also many examples of cron expressions: https://www.cnblogs.com/yanghj010/p/10875151.html

• //The Service layer writes @ servicepublic class scheduledservice {/ / cron expression / / seconds, minutes, hours, days, months and weeks / / the following represents all @ scheduled (cron = "0 35 17 * *?") Public void hello() {system. Out. Println ("Hello, you are executed!");}}
  

4. Summary: big data development is often used