/cron-utils

Cron utils for parsing, validations and human readable descriptions as well as date/time interoperability.

Primary LanguageJavaApache License 2.0Apache-2.0

cron-utils

A Java library to parse, validate, migrate crons as well as get human readable descriptions for them. The project follows the Semantic Versioning Convention and uses Apache 2.0 license.

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cron-utils is available on Maven central repository.

<dependency>
    <groupId>com.cronutils</groupId>
    <artifactId>cron-utils</artifactId>
    <version>6.0.3</version>
</dependency>

Features

  • Create arbitrary cron expressions: you can define your own cron format! Supported fields are: second, minute, hour, day of month, month, day of week, year.
  • You can flag last field as optional!
  • Supports all cron special characters: * / , -
    • Non-standard characters L, W, LW, '?' and # are supported as well!
  • Print to locale specific human readable format (Chinese, English, German, Indonesian, Korean, Spanish and Turkish are fully supported. Dutch, French, Italian, Portuguese and Russian have basic support).
  • Parse and Description process are decoupled: parse once and operate with the result!
  • Build cron expressions using CronBuilder:
    • no need to remember fields and constraints for each cron provider
    • crons become decoupled from cron provider: anytime you can export to another format.
  • Check if cron expressions are equivalent
  • Validate if cron string expressions match a cron definition
  • Convert crons between different cron definitions: if you need to migrate expressions, CronMapper may help you!
  • Pre-defined definitions for the following cron libraries are provided:
  • Obtain last/next execution time as well as time from last execution/time to next execution.
  • Need to map constants between different cron/time libraries? Use ConstantsMapper.

Usage Examples

Below we present some examples. You can find this and others in a sample repo we created to showcase cron-utils libraries!

Build cron definitions

// Define your own cron: arbitrary fields are allowed and last field can be optional
CronDefinition cronDefinition =
    CronDefinitionBuilder.defineCron()
        .withSeconds().and()
        .withMinutes().and()
        .withHours().and()
        .withDayOfMonth()
            .supportsHash().supportsL().supportsW().and()
        .withMonth().and()
        .withDayOfWeek()
            .withIntMapping(7, 0) //we support non-standard non-zero-based numbers!
            .supportsHash().supportsL().supportsW().and()
        .withYear().optional().and()
        .instance();

// or get a predefined instance
cronDefinition = CronDefinitionBuilder.instanceDefinitionFor(QUARTZ);

Build a cron expression

// Create a cron expression. CronMigrator will ensure you remain cron provider agnostic
import static com.cronutils.model.field.expression.FieldExpressionFactory.*;

Cron cron = CronBuilder.cron(CronDefinitionBuilder.instanceDefinitionFor(CronType.QUARTZ))
    .withYear(always())
    .withDoM(between(SpecialChar.L, 3))
    .withMonth(always())
    .withDoW(questionMark())
    .withHour(always())
    .withMinute(always())
    .withSecond(on(0))
    .instance();
// Obtain the string expression
String cronAsString = cron.asString(); // 0 * * L-3 * ? *

Parse

// Create a parser based on provided definition
CronParser parser = new CronParser(cronDefinition);
Cron quartzCron = parser.parse("0 23 * ? * 1-5 *");

Describe

// Create a descriptor for a specific Locale
CronDescriptor descriptor = CronDescriptor.instance(Locale.UK);

// Parse some expression and ask descriptor for description
String description = descriptor.describe(parser.parse("*/45 * * * * ?"));
// Description will be: "every 45 seconds"

description = descriptor.describe(quartzCron);
// Description will be: "every hour at minute 23 every day between Monday and Friday"
// which is the same description we get for the cron below:
descriptor.describe(parser.parse("0 23 * ? * MON-FRI *"));

Migrate

// Migration between cron libraries has never been so easy!
// Turn cron expressions into another format by using CronMapper:
CronMapper cronMapper = CronMapper.fromQuartzToCron4j();

Cron cron4jCron = cronMapper.map(quartzCron);
// and to get a String representation of it, we can use
cron4jCron.asString();//will return: 23 * * * 1-5

Validate

cron4jCron.validate()

Calculate time from/to execution

// Get date for last execution
ZonedDateTime now = ZonedDateTime.now();
ExecutionTime executionTime = ExecutionTime.forCron(parser.parse("* * * * * ? *"));
ZonedDateTime lastExecution = executionTime.lastExecution(now);

// Get date for next execution
ZonedDateTime nextExecution = executionTime.nextExecution(now);

// Time from last execution
Duration timeFromLastExecution = executionTime.timeFromLastExecution(now);

// Time to next execution
Duration timeToNextExecution = executionTime.timeToNextExecution(now);

Map constants between libraries

// Map day of week value from Quartz to JodaTime
int jodatimeDayOfWeek =
        ConstantsMapper.weekDayMapping(
                ConstantsMapper.QUARTZ_WEEK_DAY,
                ConstantsMapper.JODATIME_WEEK_DAY
        );

Date and time formatting for humans!

Use htime - Human readable datetime formatting for Java! Despite this functionality is not bundled in the same jar, is a cron-utils project you may find useful.

// You no longer need to remember "YYYY-MM-dd KK a" patterns.
DateTimeFormatter formatter = 
	    HDateTimeFormatBuilder
		    .getInstance()
		    .forJodaTime()
		    .getFormatter(Locale.US)
		    .forPattern("June 9, 2011");
String formattedDateTime = formatter.print(lastExecution);
// formattedDateTime will be lastExecution in "dayOfWeek, Month day, Year" format

cron-utils CLI

We provide a simple CLI interface to use cron-utils right from console, without writing a new project!

  • Usage: java -jar cron-utils.jar com.cronutils.cli.CronUtilsCLI --validate -f [CRON4J|QUARTZ|UNIX] -e '<cron expression>'

  • Example: java -jar cron-utils.jar com.cronutils.cli.CronUtilsCLI --validate -f UNIX -e '* 1 * * *'

If you want a standalone jar without requiring the 'cp', build an uber jar with :

mvn assembly:assembly -DdescriptorId=jar-with-dependencies

Then, launch cli-utils (built in the target directory) with :

java -jar cron-utils-<version>-jar-with-dependencies.jar com.cronutils.cli.CronUtilsCLI --validate -f [CRON4J|QUARTZ|UNIX] -e '<cron expression>'`

Contribute & Support!

Contributions are welcome! You can contribute by

  • starring and/or Flattring this repo!
  • requesting or adding new features. Check our roadmap!
  • enhancing existing code: ex.: provide more accurate description cases
  • testing
  • enhancing documentation
  • providing translations to support new locales
  • bringing suggestions and reporting bugs
  • spreading the word
  • telling us how you use it! We look forward to list you at our wiki!

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Other cron-utils projects

You are welcome to visit and use the following cron-utils projects:

  • htime: A Java library to make it easy for humans format a date. You no longer need to remember date time formatting chars: just write an example, and you will get the appropiate formatter.
  • cron-utils-spring: A Java library to describe cron expressions in human readable language at Spring framework, using cron-utils.