Spring cron vs normal cron?

Question

I\'m trying to get a cron job working within a legacy Java/Spring/Hibernate project, so I decided to use the spring scheduler.

I want myTask.doStuff to run at 12:00

Answer 1

Taking some note from: https://www.baeldung.com/cron-expressions

A Spring Scheduled tasks is like this:

1 2 3 4 5 6 Index
- - - - - -
* * * * * * command to be executed
- - - - - -
| | | | | | 
| | | | | ------- Day of week (MON - SUN)
| | | | --------- Month (1 - 12)
| | | ----------- Day of month (1 - 31)
| |-------------- Hour (0 - 23)
| --------------- Minute (0 - 59)
----------------- Seconds (0 - 59)

From: https://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/

A Linux Cron job is like this:

1 2 3 4 5 Index
- - - - -
* * * * * command to be executed
- - - - -
| | | | |
| | | | ----- Day of week (0 - 7) (Sunday=0 or 7)
| | | ------- Month (1 - 12)
| | --------- Day of month (1 - 31)
| ----------- Hour (0 - 23)
------------- Minute (0 - 59)

Side note:

• Some article said it is possible to have a 7 optional param which is year , I have tried using latest spring and it show error, so I don't think it is working.
• If your Linux cron job expression is simple enough, seems like it is possible to just put an 0 in front and it will convert to the spring scheduled tasks expression
  • E.g. Every 5 minutes
    • */5 * * * * Linux cron job
    • 0 */5 * * * * Spring schedule tasks

Bonus: Spring Schedule Cron Generator

1. Click on Show code snippet
2. Click on Run Code snippet
3. Have fun!

$('.select2').select2({
  width: '100%'
});

//// Init ////////////
$dropdown = $("#secondsSelect");
for (let i = 1; i < 60; i++) {
  $dropdown.append($("<option />").val(i).text(i));
}
$dropdown = $("#minSelect");
for (let i = 1; i < 60; i++) {
  $dropdown.append($("<option />").val(i).text(i));
}
$dropdown = $("#hoursSelect");
for (let i = 1; i < 24; i++) {
  $dropdown.append($("<option />").val(i).text(i));
}
$dropdown = $("#dayOfMonthSelect");
for (let i = 1; i < 32; i++) {
  $dropdown.append($("<option />").val(i).text(i));
}
//// Init End ////////////


$('.select2').on('select2:select', function(e) {
  let value = e.params.data.id;
  let prevValue = $(this).val().length > 0 ? $(this).val()[0] : null;

  if (value != parseInt(value)) {
    $(this).val(value).change();
  } else if (prevValue != parseInt(prevValue)) {
    $(this).val(value).change();
  }
  calculateSpringCron();
});

let r = function(dropdown) {
  return dropdown.val().join(",");

}

let calculateSpringCron = function() {

  let result = [
    r($("#secondsSelect")),
    r($("#minSelect")),
    r($("#hoursSelect")),
    r($("#dayOfMonthSelect")),
    r($("#monthsSelect")),
    r($("#weekdaySelect")),
  ];

  $("#result").val(result.join(" "));

  $("#result-expand").html(result.join(" &nbsp; &nbsp;"))

}

calculateSpringCron();

.ms-container {
  display: flex;
  flex-direction: column;
  width: 100%;
  padding-left: 3em;
  padding-right: 3em;
  background: none !important;
  padding-bottom: 5em;
}

<link href="https://cdnjs.cloudflare.com/ajax/libs/multi-select/0.9.12/css/multi-select.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/multi-select/0.9.12/js/jquery.multi-select.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">

<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>

<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.8/css/select2.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.8/js/select2.min.js"></script>

<div class="row">
  <div class="col-12">
    <h1>Spring Schedule Cron Generator</h1>
  </div>
</div>
<div class="row">
  <div class="col-4">
    Seconds:
    <select id="secondsSelect" class="select2" name="states[]" multiple="multiple">
      <option value="*" selected="selected">Every seconds</option>
      <option value="*/2">Every even seconds</option>
      <option value="1-59/2">Every odd seconds</option>
      <option value="*/5">Every 5 seconds</option>
      <option value="*/10">Every 10 seconds</option>
      <option value="*/15">Every 15 seconds</option>
      <option value="*/30">Every 30 seconds</option>
    </select>
  </div>
  <div class="col-4">
    Minutes:
    <select id="minSelect" class="select2" name="states[]" multiple="multiple">
      <option value="*" selected="selected">Every minutes</option>
      <option value="*/2">Every even minutes</option>
      <option value="1-59/2">Every odd minutes</option>
      <option value="*/5">Every 5 minutes</option>
      <option value="*/10">Every 10 minutes</option>
      <option value="*/15">Every 15 minutes</option>
      <option value="*/30">Every 30 minutes</option>
    </select>
  </div>
  <div class="col-4">
    Hours:
    <select id="hoursSelect" class="select2" name="states[]" multiple="multiple">
      <option value="*" selected="selected">Every hour</option>
      <option value="*/2">Every even hour</option>
      <option value="1-11/2">Every odd hour</option>
      <option value="*/3">Every 3 hour</option>
      <option value="*/4">Every 4 hour</option>
      <option value="*/6">Every 6 hour</option>
    </select>
  </div>
</div>

<div class="row">
</div>

<div class="row">
  <div class="col-4">
    Days of month:
    <select id="dayOfMonthSelect" class="select2" name="states[]" multiple="multiple">
      <option value="*" selected="selected">Every day of month</option>
      <option value="*/2">Even day of month</option>
      <option value="1-31/2">Odd day of month</option>
      <option value="*/5">Every 5 days of month (5,10,15...)</option>
      <option value="*/10">Every 10 days of month (10,20,30...)</option>
    </select>
  </div>
  <div class="col-4">
    Months:
    <select id="monthsSelect" class="select2" name="states[]" multiple="multiple">
      <option value="*" selected="selected">Every month</option>
      <option value="*/2">Even months</option>
      <option value="1-11/2">Odd months</option>
      <option value="*/4">Every 4 months</option>
      <option value="*/6">Every 6 months(half year)</option>
      <option value="1">Jan</option>
      <option value="2">Feb</option>
      <option value="3">Mar</option>
      <option value="4">Apr</option>
      <option value="5">May</option>
      <option value="6">Jun</option>
      <option value="7">Jul</option>
      <option value="8">Aug</option>
      <option value="9">Sep</option>
      <option value="10">Oct</option>
      <option value="11">Nov</option>
      <option value="12">Dec</option>
    </select>
  </div>
  <div class="col-4">
    Weekday:
    <select id="weekdaySelect" class="select2" name="states[]" multiple="multiple">
      <option value="*" selected="selected">Every weekday</option>
      <option value="MON-FRI">Weekdays (MON-FRI)</option>
      <option value="SAT,SUN">Weekend</option>
      <option value="SUN">SUN</option>
      <option value="MON">MON</option>
      <option value="TUE">TUE</option>
      <option value="WED">WED</option>
      <option value="THU">THU</option>
      <option value="FRI">FRI</option>
      <option value="SAT">MON</option>
    </select>
  </div>
</div>
<div class="row">
  <div class="col-12">
    Result:
    <input id="result" class="form-control" /> With a bit of seperation for better viewing:<br/>
    <h1 id="result-expand"></h1>
  </div>
</div>

Answer 2

Spring Scheduled tasks are not in the same format as cron expressions.

They don't follow the same format as UNIX cron expressions.

There are only 6 fields: second, minute, hour, day of month, month, day(s) of week. Asterisk (*) means match any. */X means "every X" (see examples). Numeric days of the week do not work for me. Besides, "MON-FRI" is much easier to read. Here are some example expressions:

"0 0 18 * * MON-FRI" means every weekday at 6:00 PM.

"0 0 */1 * * *" means every hour on the hour.

"0 0 */8 * * *" means every 8 hours on the hour.

"0 0 12 1 * *" means 12:00 PM on the first day of every month.

Here you can find some additional information: http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/scheduling/support/CronSequenceGenerator.html

Also you may find the spring documentation useful: https://docs.spring.io/spring-framework/docs/current/spring-framework-reference/integration.html#scheduling