Spring Scheduler starting at 30 minutes after a given hour and then scheduling every 30 minutes

not so trivial, you must use 2 different schedulers, because the cron regex doesn't support this case:

 

package com.example.crondemo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import org.springframework.scheduling.support.CronTrigger;


@SpringBootApplication
public class CrondemoApplication implements CommandLineRunner {
    @Autowired
    ThreadPoolTaskScheduler threadPoolTaskScheduler;

    public static void main(String[] args) {
        SpringApplication.run(CrondemoApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        // CronTrigger cronTrigger = new CronTrigger("0 30/30 19-22 * * *");  // this at 19:30 20:30...
        CronTrigger cronTrigger1 = new CronTrigger("0 30 0-8 * * *"); // this is also 20:30 21:30...
        CronTrigger cronTrigger2 = new CronTrigger("0 0 1-8 * * *"); // this is also 20:30 21:30...

        threadPoolTaskScheduler.schedule(
                new RunnableTask("Hello Pierluigi1"),
                cronTrigger1
        );
        threadPoolTaskScheduler.schedule(
                new RunnableTask("Hello Pierluigi2"),
                cronTrigger2
        );
    }
}

 

package com.example.crondemo;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;


@Configuration
public class MyConfig {
    @Bean
    public ThreadPoolTaskScheduler threadPoolTaskScheduler(){
        ThreadPoolTaskScheduler threadPoolTaskScheduler
                = new ThreadPoolTaskScheduler();
        threadPoolTaskScheduler.setPoolSize(5);
        threadPoolTaskScheduler.setThreadNamePrefix(
                "ThreadPoolTaskScheduler");
        return threadPoolTaskScheduler;
    }
}

 
package com.example.crondemo;

import java.util.Date;

class RunnableTask implements Runnable{
    private String message;

    public RunnableTask(String message){
        this.message = message;
    }

    @Override
    public void run() {
        System.out.println(new Date()+" Runnable Task with " + message
                +" on thread "+Thread.currentThread().getName());
    }
}

The output is:

Tue Nov 23 00:30:21 CET 2021 Runnable Task with Hello Pierluigi1 on thread ThreadPoolTaskScheduler1
Tue Nov 23 01:00:00 CET 2021 Runnable Task with Hello Pierluigi2 on thread ThreadPoolTaskScheduler2
Tue Nov 23 01:30:00 CET 2021 Runnable Task with Hello Pierluigi1 on thread ThreadPoolTaskScheduler1
Tue Nov 23 02:00:00 CET 2021 Runnable Task with Hello Pierluigi2 on thread ThreadPoolTaskScheduler3
Tue Nov 23 02:30:00 CET 2021 Runnable Task with Hello Pierluigi1 on thread ThreadPoolTaskScheduler2
Tue Nov 23 03:00:00 CET 2021 Runnable Task with Hello Pierluigi2 on thread ThreadPoolTaskScheduler4
Tue Nov 23 03:30:12 CET 2021 Runnable Task with Hello Pierluigi1 on thread ThreadPoolTaskScheduler1