Cronsmith - The Ultimate Cron Expression Generator & Parser

Cronsmith

Are cron expressions sometimes difficult to understand? Let's try a different approach to creating scheduled tasks.

Cronsmith is a powerful and versatile Java utility library designed for handling complex cron expressions in an intuitive, object-oriented manner. It offers a highly flexible and comprehensive API for generating, parsing, and scheduling cron-based tasks with ease.

Built for seamless integration, Cronsmith provides full support for both Spring and Quartz cron expressions, ensuring compatibility with widely used scheduling frameworks. Moreover, it extends traditional cron syntax by introducing advanced patterns — such as multiple numbers combined with 'L' (last) and 'W' (weekday)—which were previously unsupported, offering greater precision and flexibility in scheduling.

Cronsmith Github Repository
paganini2008/cronsmith

Features

1. Object-Oriented CronExpression Builder

Cronsmith allows developers to construct complex cron expressions in an intuitive, object-oriented manner. This approach enables easy customization and avoids the need for manual string construction.

Example:

@Test
    public void testA() {
        CronExpression cronExpression = new CronBuilder().everySecond(5);
        System.out.println(cronExpression.toString());
        assertEquals("*/5 * * * * ?", cronExpression.toString());
    }

    @Test
    public void testB() {
        CronExpression cronExpression = new CronBuilder().everyMinute(5).second(5).andSecond(10)
                .toSecond(30).andSecond(32).toSecond(59, 2);
        System.out.println(cronExpression.toString());
        assertEquals("5,10-30,32/2 */5 * * * ?", cronExpression.toString());
    }

    @Test
    public void testC() {
        CronExpression cronExpression = new CronBuilder().everyMonth().day(10).andDay(15).andDay(16)
                .andLastDay().everyHour(2).everyMinute(5);
        System.out.println(cronExpression.toString());
        assertEquals("0 */5 */2 10,15,16,L * ?", cronExpression.toString());
    }

    @Test
    public void testD() {
        CronExpression cronExpression = new CronBuilder().everyMonth(3).day(10).andLastWeekday()
                .hour(12).minute(1).toMinute(15, 1);
        System.out.println(cronExpression.toString());
        assertEquals("0 1-15 12 10,LW */3 ?", cronExpression.toString());
    }

    @Test
    public void testE() {
        CronExpression cronExpression =
                new CronBuilder().everyMonth().everyWeek().Mon().toFri().at(15, 10);
        System.out.println(cronExpression.toString());
        assertEquals("0 10 15 ? * MON-FRI", cronExpression.toString());
    }

    @Test
    public void testF() {
        CronExpression cronExpression = new CronBuilder().everyMonth().dayOfWeek(3, 6).everyHour(2);
        System.out.println(cronExpression.toString());
        assertTrue(cronExpression.toString().equals("0 0 */2 ? * SAT#3"));
    }

    @Test
    public void testG() {
        CronExpression cronExpression =
                new CronBuilder().year(2025).Mar().toSept().everyWeek().everyWeekday().at(9, 10);
        System.out.println(cronExpression.toString());
        assertTrue(cronExpression.toString().equals("0 10 9 ? MAR-SEP MON-FRI 2025"));
    }

    @Test
    public void testH() {
        CronExpression cronExpression =
                new CronBuilder().year(2025).toYear(2028).everyMonth(2).lastDay().hour(12);
        System.out.println(cronExpression.toString());
        assertEquals("0 0 12 L */2 ? 2025-2028", cronExpression.toString());
    }

    @Test
    public void testI() {
        CronExpression cronExpression = new CronBuilder().everyYear().June().andJuly().andAug()
                .latestWeekday(15).hour(10).toHour(18, 2);
        System.out.println(cronExpression.toString());
        assertEquals("0 0 10-18/2 15W JUN,JUL,AUG ?", cronExpression.toString());
    }

    @Test
    public void testJ() {
        CronExpression cronExpression = new CronBuilder().everyYear(2).Mar().andApr().andMay()
                .toDec().everyWeek(2).Tues().toFri().hour(10).andHour(12).toHour(22).everyMinute()
                .second(10).andSecond(20).andSecond(30);
        System.out.println(cronExpression.toString());
        assertEquals("10,20,30 * 10,12-22 ? MAR,APR,MAY-DEC TUE-FRI 2025/2",
                cronExpression.toString());
    }

    @Test
    public void testK() {
        CronExpression cronExpression = new CronBuilder().year(2025).toYear(2030).andYear(2035)
                .toEnd(2).everyMonth(2, 2).dayOfWeek(2, DayOfWeek.TUESDAY)
                .and(3, DayOfWeek.WEDNESDAY).andLastFri().hour(2).andHour(3).andHour(4)
                .toHour(17, 2).minute(0).toMinute(12, 3).andMinute(15).toMinute(40, 2).andMinute(46)
                .andMinute(48).andMinute(50).everySecond(5);
        System.out.println(cronExpression.toString());
        assertEquals(
                "*/5 0-12/3,15-40/2,46,48,50 2,3,4-17/2 ? FEB-DEC/2 TUE#2,WED#3,5L 2025-2030,2035/2",
                cronExpression.toString());
    }

    @Test
    public void testL() {
        CronExpression cronExpression = new CronBuilder().everyYear(2025, 4).everyMonth(5, 1)
                .day(10).andDay(15).andDay(20).andLastDay(2).hour(10).toHour(15, 1).at(10, 0)
                .andSecond(15).andSecond(30).andSecond(45);
        System.out.println(cronExpression.toString());
        assertEquals("0,15,30,45 10 10-15 10,15,20,L-2 MAY-DEC ? 2025/4",
                cronExpression.toString());
    }

    @Test
    public void testM() {
        CronExpression cronExpression = new CronBuilder().year().andYear(2026).andYear(2030)
                .toEnd(2).Mar().andJuly().andSept().dayOfWeek(1, DayOfWeek.SATURDAY)
                .and(2, DayOfWeek.THURSDAY).andLast(DayOfWeek.FRIDAY).hour(0).toHour(12, 3)
                .everyMinute(10).second(0).andSecond(15).andSecond(30).andSecond(45).toSecond(59);
        System.out.println(cronExpression.toString());
        assertEquals("0,15,30,45/1 */10 0-12/3 ? MAR,JUL,SEP SAT#1,THU#2,5L 2025,2026,2030/2",
                cronExpression.toString());
    }

2. Cron Expression String Parsing and Reverse Engineering to CronExpression

Cronsmith includes a powerful parser built with ANTLR, allowing you to parse an existing cron expression string and convert it back into a structured CronExpression object.

Example:

    @Test
    public void testA() {
        String cron = "0 0 12 * * ?";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testB() {
        String cron = "0 15 10 ? * MON-FRI";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testC() {
        String cron = "0 10,20,30 9-17 L * ?";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testD() {
        String cron = "1,3,5,7,9 3-30/3 12-16 ? * TUE#1";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testE() {
        String cron = "0 0 6 ? 1-5 MON,WED,FRI";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testF() {
        String cron = "*/5 1 12,15,18-22 LW * ? 2025";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testG() {
        String cron = "0 1 0-12,15,16-22/2 ? * 1-5 2025-2028";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testH() {
        String cron = "0 1,5,7,13,29,45 12/2 5,10,27W,L-1 APR-NOV ?";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testI() {
        String cron = "5/1 */5 12 ? 1-9 3#1,5#2,6L";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testJ() {
        String cron = "*/5 1,3,5/1 12-16 1,3,20,LW MAR-SEP ? 2026/1";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testK() {
        String cron = "5-30/7 0-12/3,15-45/2 2,3,4-17/2 ? JAN-JUL MON-THU/2 2025-2033";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testL() {
        String cron = "0,15,30,45/1 */10 0-12/3 ? MAR,JUL,SEP SAT#1,THU#2,5L 2025,2026,2030/2";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

    @Test
    public void testM() {
        String cron = "*/2 0 12 1,5,9,22,L */2 ? 2025/2";
        CronExpression cronExpression = CRON.parse(cron);
        System.out.println(cronExpression);
        assertEquals(cron, cronExpression.toString());
    }

Parse Tree:

cron
    second
        secondField
            rangeWithStep
                5
                -
                30
                /
                7
    <missing SPACE>
    minute
        minuteField
            rangeWithStep
                0
                -
                12
                /
                3
        ,
        minuteField
            rangeWithStep
                15
                -
                45
                /
                2
    <missing SPACE>
    hour
        hourField
            2
        ,
        hourField
            3
        ,
        hourField
            rangeWithStep
                4
                -
                17
                /
                2
    <missing SPACE>
    dayOfMonth
        dayOfMonthField
            ?
    <missing SPACE>
    month
        monthField
            monthRange
                monthName
                    JAN
                -
                monthName
                    JUL
    <missing SPACE>
    dayOfWeek
        dayOfWeekField
            weekdayRangeWithStep
                dayOfWeekName
                    MON
                -
                dayOfWeekName
                    THU
                /
                2
    year
        yearField
            yearRange
                2025
                -
                2030
    <EOF>

Retrieve next date and times from CronExpression

public static void main(String[] args) {
   int N = 100; // Retrieve 100 items
   String cron = "10 0 12 LW 1/2 ?";
   CronExpression cronExpression = CRON.parse(cron);
   System.out.println(cronExpression);
   cronExpression.consume(l -> {
       System.out.println(l);
   }, N);
}

// Console:
// 2025-05-30T12:00:10
// 2025-07-31T12:00:10
// 2025-09-30T12:00:10
// 2025-11-28T12:00:10
// 2026-01-30T12:00:10
// 2026-03-31T12:00:10
// 2026-05-29T12:00:10
// 2026-07-31T12:00:10
// 2026-09-30T12:00:10
// 2026-11-30T12:00:10
// 2027-01-29T12:00:10
// 2027-03-31T12:00:10
// 2027-05-31T12:00:10
// 2027-07-30T12:00:10
// 2027-09-30T12:00:10
// 2027-11-30T12:00:10
// 2028-01-31T12:00:10
// 2028-03-31T12:00:10
// 2028-05-31T12:00:10
// ...

3. Built-in Scheduler

Cronsmith provides a built-in scheduler that allows you to execute tasks at specified intervals based on cron expressions. This feature makes it easy to schedule repetitive tasks efficiently.

Example: Scheduling a Task Every 5 Seconds

private ScheduledExecutorService scheduledExecutorService;

@Before
public void start() {
    scheduledExecutorService =
                Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors() * 2);
}

@Test
public void testSchedulerAndRunTenTimes() {
    int N = 10; // Run 10 times
    final CountDownLatch latch = new CountDownLatch(N);
    final AtomicInteger counter = new AtomicInteger();

    CronFuture future = new CronBuilder()
        .everySecond(5)
        .scheduler(scheduledExecutorService)
        .setDebuged(false)
        .runTask(() -> {
            System.out.println("Run task_" + counter.incrementAndGet());
            latch.countDown();
        }, N);

    try {
        latch.await();
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }

    future.cancel(true);
    assertTrue(future.isDone() && counter.get() == N);
}

@After
public void release() {
    scheduledExecutorService.shutdown();
}

4. Advanced Part

Can specify day of year

public static void main(String[] args) {
   int N = 1000;
   DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
   new CronBuilder().setZoneId(ZoneId.of("UTC")).year(2025).day(208).andDay(330).toLastDay()
                .at(12, 0).consume(ldt -> {
                    System.out.println(ldt.format(dtf));
                }, N);
}
// Console: 
// 2025-07-27 12:00:00
// 2025-11-26 12:00:00
// 2025-11-27 12:00:00
// 2025-11-28 12:00:00
// 2025-11-29 12:00:00
// 2025-11-30 12:00:00
// 2025-12-01 12:00:00
// 2025-12-02 12:00:00
// 2025-12-03 12:00:00
// 2025-12-04 12:00:00
// 2025-12-05 12:00:00
// 2025-12-06 12:00:00
// ...

Can specify week of year

public static void main(String[] args) {
    int N = 1000;
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    new CronBuilder().setZoneId(ZoneId.of("UTC")).everyYear().week(40).andWeek(45).Mon().toFri()
                .at(12, 0).consume(ldt -> {
                    System.out.println(ldt.format(dtf));
                }, N);
}
// Console: 
// 2025-09-29 12:00:00
// 2025-09-30 12:00:00
// 2025-10-01 12:00:00
// 2025-10-02 12:00:00
// 2025-10-03 12:00:00
// 2025-11-03 12:00:00
// 2025-11-04 12:00:00
// 2025-11-05 12:00:00
// 2025-11-06 12:00:00
// 2025-11-07 12:00:00
// 2026-09-28 12:00:00
// 2026-09-29 12:00:00
// 2026-09-30 12:00:00
// 2026-10-01 12:00:00
// 2026-10-02 12:00:00
// ...

Installation

Support Jdk1.8 or later

To use Cronsmith in your Java project, add the following dependency to your pom.xml (if using Maven):

<dependency>
    <groupId>com.github.paganini2008</groupId>
    <artifactId>cronsmith</artifactId>
    <version>1.0.0-RC1</version>
</dependency>

If using Gradle:

dependencies {
    implementation 'com.github.paganini2008:cronsmith:1.0.0-RC1'
}

Getting Started

1. Add Cronsmith as a dependency in your project.
2. Use CronBuilder to create complex cron expressions.
3. Parse existing cron expressions using CRON.parse().
4. Schedule tasks using the built-in scheduler.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Cronsmith Github Repository

paganini2008/cronsmith