Add execution metadata to tasks and scheduled tasks

This commit adds new information about the execution and scheduling of
tasks.

The `Task` type now exposes the `TaskExecutionOutcome` of the latest
execution; this includes the instant the execution started, the
execution outcome and any thrown exception.

The `ScheduledTask` contract can now provide the time when the next
execution is scheduled.

Closes gh-24560

Author: bclozel

Diff for: spring-context/src/main/java/org/springframework/scheduling/config/ScheduledTask.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,7 +16,9 @@
 
 package org.springframework.scheduling.config;
 
+import java.time.Instant;
 import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
 
 import org.springframework.lang.Nullable;
 
@@ -25,6 +27,7 @@
  * used as a return value for scheduling methods.
  *
  * @author Juergen Hoeller
+ * @author Brian Clozel
  * @since 4.3
  * @see ScheduledTaskRegistrar#scheduleCronTask(CronTask)
  * @see ScheduledTaskRegistrar#scheduleFixedRateTask(FixedRateTask)
@@ -76,6 +79,22 @@ public void cancel(boolean mayInterruptIfRunning) {
 		}
 	}
 
+	/**
+	 * Return the next scheduled execution of the task, or {@code null}
+	 * if the task has been cancelled or no new execution is scheduled.
+	 * @since 6.2
+	 */
+	@Nullable
+	public Instant nextExecution() {
+		if (this.future != null && !this.future.isCancelled()) {
+			long delay = this.future.getDelay(TimeUnit.MILLISECONDS);
+			if (delay > 0) {
+				return Instant.now().plusMillis(delay);
+			}
+		}
+		return null;
+	}
+
 	@Override
 	public String toString() {
 		return this.task.toString();

Diff for: spring-context/src/main/java/org/springframework/scheduling/config/Task.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.scheduling.config;
 
+import java.time.Instant;
+
 import org.springframework.util.Assert;
 
 /**
@@ -24,20 +26,24 @@
  *
  * @author Chris Beams
  * @author Juergen Hoeller
+ * @author Brian Clozel
  * @since 3.2
  */
 public class Task {
 
 	private final Runnable runnable;
 
+	private TaskExecutionOutcome lastExecutionOutcome;
+
 
 	/**
 	 * Create a new {@code Task}.
 	 * @param runnable the underlying task to execute
 	 */
 	public Task(Runnable runnable) {
 		Assert.notNull(runnable, "Runnable must not be null");
-		this.runnable = runnable;
+		this.runnable = new OutcomeTrackingRunnable(runnable);
+		this.lastExecutionOutcome = TaskExecutionOutcome.create();
 	}
 
 
@@ -48,10 +54,45 @@ public Runnable getRunnable() {
 		return this.runnable;
 	}
 
+	/**
+	 * Return the outcome of the last task execution.
+	 * @since 6.2
+	 */
+	public TaskExecutionOutcome getLastExecutionOutcome() {
+		return this.lastExecutionOutcome;
+	}
 
 	@Override
 	public String toString() {
 		return this.runnable.toString();
 	}
 
+
+	private class OutcomeTrackingRunnable implements Runnable {
+
+		private final Runnable runnable;
+
+		public OutcomeTrackingRunnable(Runnable runnable) {
+			this.runnable = runnable;
+		}
+
+		@Override
+		public void run() {
+			try {
+				Task.this.lastExecutionOutcome = Task.this.lastExecutionOutcome.start(Instant.now());
+				this.runnable.run();
+				Task.this.lastExecutionOutcome = Task.this.lastExecutionOutcome.success();
+			}
+			catch (Throwable exc) {
+				Task.this.lastExecutionOutcome = Task.this.lastExecutionOutcome.failure(exc);
+				throw exc;
+			}
+		}
+
+		@Override
+		public String toString() {
+			return this.runnable.toString();
+		}
+	}
+
 }

Diff for: spring-context/src/main/java/org/springframework/scheduling/config/TaskExecutionOutcome.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.scheduling.config;
+
+import java.time.Instant;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * Outcome of a {@link Task} execution.
+ * @param executionTime the instant when the task execution started, {@code null} if the task has not started.
+ * @param status        the {@link Status} of the execution outcome.
+ * @param throwable     the exception thrown from the task execution, if any.
+ * @author Brian Clozel
+ * @since 6.2
+ */
+public record TaskExecutionOutcome(@Nullable Instant executionTime, Status status, @Nullable Throwable throwable) {
+
+	TaskExecutionOutcome start(Instant executionTime) {
+		return new TaskExecutionOutcome(executionTime, Status.STARTED, null);
+	}
+
+	TaskExecutionOutcome success() {
+		Assert.state(this.executionTime != null, "Task has not been started yet");
+		return new TaskExecutionOutcome(this.executionTime, Status.SUCCESS, null);
+	}
+
+	TaskExecutionOutcome failure(Throwable throwable) {
+		Assert.state(this.executionTime != null, "Task has not been started yet");
+		return new TaskExecutionOutcome(this.executionTime, Status.ERROR, throwable);
+	}
+
+	static TaskExecutionOutcome create() {
+		return new TaskExecutionOutcome(null, Status.NONE, null);
+	}
+
+
+	/**
+	 * Status of the task execution outcome.
+	 */
+	public enum Status {
+		/**
+		 * The task has not been executed so far.
+		 */
+		NONE,
+		/**
+		 * The task execution has been started and is ongoing.
+		 */
+		STARTED,
+		/**
+		 * The task execution finished successfully.
+		 */
+		SUCCESS,
+		/**
+		 * The task execution finished with an error.
+		 */
+		ERROR
+	}
+}