BAEL-4322 add sample codes for dynamic delay setting (eugenp#10531)

Co-authored-by: Yavuz Tas <[email protected]>

spring-scheduling/src/main/java/com/baeldung/scheduling/dynamic/DynamicSchedulingConfig.java

@@ -0,0 +1,45 @@
+package com.baeldung.scheduling.dynamic;
+
+import java.time.Instant;
+import java.util.Date;
+import java.util.Optional;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.scheduling.annotation.SchedulingConfigurer;
+import org.springframework.scheduling.config.ScheduledTaskRegistrar;
+
+@Configuration
+@ComponentScan("com.baeldung.scheduling.dynamic")
+@EnableScheduling
+public class DynamicSchedulingConfig implements SchedulingConfigurer {
+
+    @Autowired
+    private TickService tickService;
+
+    @Bean
+    public Executor taskExecutor() {
+        return Executors.newSingleThreadScheduledExecutor();
+    }
+
+    @Override
+    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
+        taskRegistrar.setScheduler(taskExecutor());
+        taskRegistrar.addTriggerTask(
+          () -> tickService.tick(),
+          context -> {
+              Optional<Date> lastCompletionTime =
+                Optional.ofNullable(context.lastCompletionTime());
+              Instant nextExecutionTime =
+                lastCompletionTime.orElseGet(Date::new).toInstant()
+                  .plusMillis(tickService.getDelay());
+              return Date.from(nextExecutionTime);
+          }
+        );
+    }
+
+}

spring-scheduling/src/main/java/com/baeldung/scheduling/dynamic/TickService.java

@@ -0,0 +1,22 @@
+package com.baeldung.scheduling.dynamic;
+
+import org.springframework.stereotype.Service;
+
+@Service
+public class TickService {
+
+    private long delay = 0;
+
+    public long getDelay() {
+        this.delay += 1000;
+        System.out.println("delaying " + this.delay + " milliseconds...");
+        return this.delay;
+    }
+
+    public void tick() {
+        final long now = System.currentTimeMillis() / 1000;
+        System.out
+          .println("schedule tasks with dynamic delay - " + now);
+    }
+
+}

spring-scheduling/src/test/java/com/baeldung/scheduling/DynamicSchedulingIntegrationTest.java

@@ -0,0 +1,19 @@
+package com.baeldung.scheduling;
+
+import com.baeldung.scheduling.dynamic.DynamicSchedulingConfig;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = {
+  DynamicSchedulingConfig.class}, loader = AnnotationConfigContextLoader.class)
+public class DynamicSchedulingIntegrationTest {
+
+    @Test
+    public void testTickServiceTick() throws InterruptedException {
+        Thread.sleep(6000);
+    }
+}