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

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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>3.1.6</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 (English, German, Korean and Spanish are fully supported. Dutch, French, Italian and Portuguese have basic support).
  • Parse and Description process are decoupled: parse once and operate with the result!
  • Validate if cron string expressions match a cron definition using CronValidator
  • 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

Build cron definitions

//define your own cron: arbitrary fields are allowed and last field can be optional
CronDefinition cronDefinition =
    CronDefinitionBuilder.define()
        .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().and()
        .lastFieldOptional()
        .instance();

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

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 is easy!
//Turn cron expressions into another format by using CronMapper:
CronMapper cronMapper =
        new CronMapper(
                cronDefinition,
                CronDefinitionBuilder.instanceDefinitionFor(CRON4J)
        );
Cron cron4jCron = cronMapper.map(quartzCron);
//and to get a String representation of it, we can use
cron4jCron.asString();//will return: 23 * * * 1-5

Validate

//Validate if a string expression matches a cron definition:
CronValidator quartzValidator = new CronValidator(cronDefinition);

//getting a boolean result:
quartzValidator.isValid("0 23 ? * * MON-FRI *");

//or returning same string if valid and raising an exception if invalid
quartzValidator.validate("0 23 ? * * MON-FRI *");

Calculate time from/to execution

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

//Get date for next execution
DateTime 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

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!

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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.

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