Cron expression

README.md

@@ -83,19 +83,24 @@ the job will be executed once 10 seconds after it has been scheduled.
 
 ### Cron
 Schedules can be created using [cron expressions](https://en.wikipedia.org/wiki/Cron#CRON_expression).
-This feature is made possible by the use of [cron-utils](https://github.com/jmrozanec/cron-utils).
-So to use cron expression, cron-utils should be added in the project:
+This feature is made possible by the use of [cron library](https://github.com/frode-carlsen/cron). This library is very lightweight: it has no dependency and is made of a single Java class of 650 lines of code.
+
+So to use cron expression, this library has to be added:
 ```xml
 <dependency>
-    <groupId>com.cronutils</groupId>
-    <artifactId>cron-utils</artifactId>
-    <version>9.1.6</version>
+    <groupId>ch.eitchnet</groupId>
+    <artifactId>cron</artifactId>
+    <version>1.6.2</version>
 </dependency>
 ```
+
 Then to create a job which is executed every hour at the 30th minute,
-you can create the schedule: `CronSchedule.parseQuartzCron("0 30 * * * ? *")`.
+you can create the schedule: `CronExpressionSchedule.parse("30 * * * *")`.
+
+Cron expression should be checked using a tool like [Cronhub](https://crontab.cronhub.io/).
 
-Cron expression should be created and checked using a tool like [Cron Maker](http://www.cronmaker.com/).
+Cron-utils was the default Cron implementation before Wisp 2.2.2. This has [changed in version 2.3.0](/../../issues/14).
+Documentation about cron-utils implementation can be found at [Wisp 2.2.2](/../../tree/2.2.2#cron).
 
 ### Custom schedules
 Custom schedules can be created,

pom.xml

@@ -4,7 +4,7 @@
 
 	<groupId>com.coreoz</groupId>
 	<artifactId>wisp</artifactId>
-	<version>2.2.3-SNAPSHOT</version>
+	<version>2.3.1-SNAPSHOT</version>
 	<packaging>jar</packaging>
 
 	<name>Wisp Scheduler</name>
@@ -176,6 +176,12 @@
 			<version>9.1.6</version>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>ch.eitchnet</groupId>
+			<artifactId>cron</artifactId>
+			<version>1.6.2</version>
+			<optional>true</optional>
+		</dependency>
 
 		<dependency>
 			<groupId>junit</groupId>

src/main/java/com/coreoz/wisp/schedule/cron/CronExpressionSchedule.java

@@ -0,0 +1,71 @@
+package com.coreoz.wisp.schedule.cron;
+
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+import com.coreoz.wisp.schedule.Schedule;
+
+import fc.cron.CronExpression;
+
+/**
+ * A {@link Schedule} based on a <a href="https://en.wikipedia.org/wiki/Cron#CRON_expression">
+ * Cron expression</a>.<br>
+ * <br>
+ * This class depends on <a href="https://github.com/frode-carlsen/cron">Cron library</a>,
+ * so this dependency has to be in the classpath in order to be able to use {@link CronExpressionSchedule}.
+ * Since the Cron library is marked as optional in Wisp, it has to be
+ * <a href="https://github.com/Coreoz/Wisp#cron">explicitly referenced in the project dependency configuration</a>
+ * (pom.xml, build.gradle, build.sbt etc.).<br>
+ * <br>
+ * See also {@link CronExpression} for format details and implementation.
+ */
+public class CronExpressionSchedule implements Schedule {
+
+	private final CronExpression cronExpression;
+	private final ZoneId zoneId;
+
+	public CronExpressionSchedule(CronExpression cronExpression, ZoneId zoneId) {
+		this.cronExpression = cronExpression;
+		this.zoneId = zoneId;
+	}
+
+	public CronExpressionSchedule(CronExpression cronExpression) {
+		this(cronExpression, ZoneId.systemDefault());
+	}
+
+	@Override
+	public long nextExecutionInMillis(long currentTimeInMillis, int executionsCount, Long lastExecutionTimeInMillis) {
+		Instant currentInstant = Instant.ofEpochMilli(currentTimeInMillis);
+		try {
+			return cronExpression.nextTimeAfter(ZonedDateTime.ofInstant(
+				currentInstant,
+				zoneId
+			)).toEpochSecond() * 1000L;
+		} catch (IllegalArgumentException e) {
+			return Schedule.WILL_NOT_BE_EXECUTED_AGAIN;
+		}
+	}
+
+	@Override
+	public String toString() {
+		return cronExpression.toString();
+	}
+
+	/**
+	 * Create a {@link Schedule} from a cron expression based on the Unix format,
+	 * e.g. 1 * * * * for each minute.
+	 */
+	public static CronExpressionSchedule parse(String cronExpression) {
+		return new CronExpressionSchedule(CronExpression.createWithoutSeconds(cronExpression));
+	}
+
+	/**
+	 * Create a {@link Schedule} from a cron expression based on the Unix format, but accepting a second field as the first one,
+	 * e.g. 29 * * * * * for each minute at the second 29, for instance 12:05:29.
+	 */
+	public static CronExpressionSchedule parseWithSeconds(String cronExpression) {
+		return new CronExpressionSchedule(CronExpression.create(cronExpression));
+	}
+
+}

src/main/java/com/coreoz/wisp/schedule/cron/CronSchedule.java

@@ -21,7 +21,12 @@
  * so this dependency have to be in the classpath in order to be able to use {@link CronSchedule}.
  * Since cron-utils is marked as optional, it has to be explicitly referenced in the
  * project dependency configuration (pom.xml, build.gradle, build.sbt etc.).
+ *
+ * @deprecated Use {@link CronExpressionScheduleTest} instead.
+ * This class has been deprecated to move away from cron-utils. See
+ * <a href="https://github.com/Coreoz/Wisp/issues/14">issue #14</a> for details.
  */
+@Deprecated
 public class CronSchedule implements Schedule {
 
 	private static final CronParser UNIX_CRON_PARSER = new CronParser(
@@ -68,15 +73,22 @@ public String toString() {
 	/**
 	 * Create a {@link Schedule} from a cron expression based on the Unix format,
 	 * e.g. 1 * * * * for each minute.
+	 *
+	 * @deprecated Use {@link CronExpressionScheduleTest#parse(String)} instead
 	 */
+	@Deprecated
 	public static CronSchedule parseUnixCron(String cronExpression) {
 		return new CronSchedule(UNIX_CRON_PARSER.parse(cronExpression));
 	}
 
 	/**
 	 * Create a {@link Schedule} from a cron expression based on the Quartz format,
 	 * e.g. 0 * * * * ? * for each minute.
+	 *
+	 * @deprecated Use {@link CronExpressionScheduleTest#parse(String)}
+	 * or {@link CronExpressionScheduleTest#parseWithSeconds(String)} instead
 	 */
+	@Deprecated
 	public static CronSchedule parseQuartzCron(String cronExpression) {
 		return new CronSchedule(QUARTZ_CRON_PARSER.parse(cronExpression));
 	}

src/test/java/com/coreoz/wisp/schedule/cron/CronExpressionScheduleTest.java

@@ -0,0 +1,52 @@
+package com.coreoz.wisp.schedule.cron;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.Duration;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+import org.junit.Test;
+
+public class CronExpressionScheduleTest {
+
+	@Test
+	public void should_calcule_the_next_execution_time_based_on_a_unix_cron_expression() {
+		CronExpressionSchedule everyMinuteScheduler = CronExpressionSchedule.parse("* * * * *");
+
+		// To ease calculations, next execution time are calculated from the timestamp "0".
+		// So here, the absolute timestamp for an execution in 1 minute will be 60
+		assertThat(everyMinuteScheduler.nextExecutionInMillis(0, 0, null))
+		.isEqualTo(Duration.ofMinutes(1).toMillis());
+	}
+
+	@Test
+	public void should_calcule_the_next_execution_time_based_on_a_unix_cron_expression_with_seconds() {
+		CronExpressionSchedule everyMinuteScheduler = CronExpressionSchedule.parseWithSeconds("29 * * * * *");
+
+		assertThat(everyMinuteScheduler.nextExecutionInMillis(0, 0, null))
+		// the first iteration will be the absolute timestamp "29"
+		.isEqualTo(Duration.ofSeconds(29).toMillis());
+		assertThat(everyMinuteScheduler.nextExecutionInMillis(29000 , 1, null))
+		// the second iteration will be the absolute timestamp "89"
+		.isEqualTo(Duration.ofSeconds(60 + 29).toMillis());
+	}
+
+	@Test
+	public void should_not_executed_daily_jobs_twice_a_day() {
+		CronExpressionSchedule everyMinuteScheduler = CronExpressionSchedule.parse("0 12 * * *");
+
+		ZonedDateTime augustMidday = LocalDate
+			.of(2016, 8, 31)
+			.atTime(12, 0)
+			.atZone(ZoneId.systemDefault());
+		long midday = augustMidday.toEpochSecond() * 1000;
+
+		assertThat(everyMinuteScheduler.nextExecutionInMillis(midday-1, 0, null))
+			.isEqualTo(midday);
+		assertThat(everyMinuteScheduler.nextExecutionInMillis(midday, 0, null))
+			.isEqualTo(midday + Duration.ofDays(1).toMillis());
+	}
+
+}