1, Spring Boot and tasks

1.1 asynchronous tasks

In Java applications, in most cases, interactive processing is realized through synchronization; However, when dealing with interaction with third-party systems, it is easy to cause slow response. Before, most of them used multithreading to complete such tasks. In fact, in spring 3 After X, the @ Async annotation has been built in to perfectly solve this problem.

There are two notes:

• @EnableAysnc: mark on the startup class to start the annotation development of asynchronous tasks
• @Aysnc: mark the tasks to be executed asynchronously

The basic usage is as follows:

1. Enable asynchronous task annotation support on startup class

   @EnableAsync
   @SpringBootApplication
   public class SpringbootTaskApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(SpringbootTaskApplication.class, args);
       }
   }
   

2. Mark the @ Async annotation on the method to be executed asynchronously

   @Service
   public class AsyncService {
   
       @Async
       public void hello(){
           try {
               Thread.sleep(3000);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
           System.out.println("Data processing.......");
       }
   }
   

3. Write Controller

   @RestController
   public class AsyncController {
   
       @Autowired
       AsyncService asyncService;
   
       @RequestMapping("/hello")
       public String hello(){
           asyncService.hello();
           return "success";
       }
   }
   

At this time, accessing the hello method in the Controller will immediately return the result, and the text message will be printed after 3 seconds. At this time, the method call does not have an asynchronous task. If the annotation of the asynchronous task is not enabled, the Controller will return the result after 3 seconds.

1.2 scheduled tasks

During project development, it is often necessary to perform some scheduled tasks. For example, it is necessary to analyze the log information of the previous day in the early morning of each day. Spring provides us with a way to schedule tasks asynchronously, and provides TaskExecutor and TaskScheduler interfaces.

The main notes are as follows:

• @Enablesscheduling: mark on the startup class to enable the support of annotation scheduled tasks
• @Scheduled: above the label and method, define the scheduled execution time of the modified method

The basic usage is as follows:

1. Enable timed task annotation support on the startup class

   @EnableScheduling
   @SpringBootApplication
   public class SpringbootTaskApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(SpringbootTaskApplication.class, args);
       }
   }
   

2. Mark @ Scheduled on the task to define when to execute the task

   @Service
   public class ScheduleService {
   
       /**Parameters are separated by spaces
        * second(Second, minute, hour, day of month, month, day of week
        * 0 * * * * MON-FRI
        *  [0 0/5 14,18 * * ?] At 14 o'clock sharp and 18 o'clock sharp every five minutes
        *  [0 15 10 ? * 1-6] It shall be implemented once every month from Monday to Saturday at 10:15
        *  [0 0 2 ? * 6L]At 2 a.m. on the last Saturday of each month
        *  [0 0 2 LW * ?]It is implemented once at 2 a.m. on the last working day of each month
        *  [0 0 2-4 ? * 1#1]From 2:00 a.m. to 4:00 a.m. on the first Monday of each month, it is implemented once every whole hour;
        */
       // @Scheduled(cron = "0 * * * * MON-SAT")
       //@Scheduled(cron = "0,1,2,3,4 * * * * MON-SAT")
       // @Scheduled(cron = "0-4 * * * * MON-SAT")
       @Scheduled(cron = "0 * * * * 0-7")
       public void schedule(){
           System.out.println("schedule.......");
       }
   }
   

cron expression:

field	Operating value	Run special characters
second	0-59	,，-，*，/
branch	0-59	,，-，*，/
Time	0-23	,，-，*，/
date	1-31	,，-，*，?，/，L，W，C
month	1-12	,，-，*，/
week	0-7 or SUN-SAT; 0,7 is SUN	,，-，*，?，/，L，C，#

Special characters:

Special characters	Express meaning
,	enumeration
-	section
*	arbitrarily
/	step
?	Day / week conflict match
L	last
W	weekdays
C	Calculated value after contacting calendar
#	Thursday, 4#2 the second Thursday

1.3 email tasks

Basic use

1. Introducing mail dependencies

    	<parent>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-parent</artifactId>
           <version>2.6.2</version>
           <relativePath/> <!-- lookup parent from repository -->
       </parent>
    	<dependencies>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-web</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-mail</artifactId>
           </dependency>
   
           <dependency>
               <groupId>org.projectlombok</groupId>
               <artifactId>lombok</artifactId>
               <optional>true</optional>
           </dependency>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-test</artifactId>
               <scope>test</scope>
           </dependency>
       </dependencies>
   

2. Configure email account and password

   spring:
     mail:
       username: 123@qq.com
   #    Authorization code of qq mailbox
       password: fdsafdsaaasff
   #   Configure qq's host
       host: smtp.qq.com
   

3. Test mail sending

   @SpringBootTest
   class SpringbootTaskApplicationTests {
   
       @Autowired
       JavaMailSenderImpl mailSender;
   
       @Test
       void contextLoads() {
           //Send simple email
           SimpleMailMessage simpleMail = new SimpleMailMessage();
           //Set the subject of the message
           simpleMail.setSubject("notice-Evening meeting");
           //Set the content of the message
           simpleMail.setText("7 pm:30 attend a meeting");
           //Set the sending account
           simpleMail.setFrom("123@qq.com");
           //Set the received mailbox
           simpleMail.setTo("456@163.com");
           mailSender.send(simpleMail);
       }
   
       @Test
       void contextLoads1() throws MessagingException {
           //Send complex mail
           MimeMessage mimeMessage = mailSender.createMimeMessage();
   
           //Settings can be attached
           MimeMessageHelper messageHelper = new MimeMessageHelper(mimeMessage,true);
           //Set the subject of the message
           messageHelper.setSubject("notice-Evening meeting");
           //Set the content of the message
           messageHelper.setText("<b style='color:red'>Today 7:30 attend a meeting</b>",true);
           messageHelper.addAttachment("1.jpg", new File("C:\\wallpaper\\9.jpg"));
           //Set the sending account
           messageHelper.setFrom("123@qq.com");
           //Set the received mailbox
           messageHelper.setTo("456@163.com");
   
           mailSender.send(mimeMessage);
       }
   
   }