Convert cron expression into nice description strings? Is there a library for JAVA and Objective-C?

Question

I am looking for a parser that converts a cron expression like 45 17 7 6 * * into Every year, on June 7th at 17:45 The parser should be adjustable to other languages. German for the first step.

Is there a library for a

• JAVA based Android project
• Objective-C based Iphone project.

See here for the usecase.

Solution 1

cronTrigger.getExpressionSummary()

Example:

    CronTrigger t = new CronTrigger();
    t.setCronExpression("0 30 10-13 ? * WED,FRI");
    System.out.println(""+t.getExpressionSummary());

Output:

seconds: 0
minutes: 30
hours: 10,11,12,13
daysOfMonth: ?
months: *
daysOfWeek: 4,6
lastdayOfWeek: false
nearestWeekday: false
NthDayOfWeek: 0
lastdayOfMonth: false
years: *

• Api Java Doc

Solution 2

You may find cron-utils useful for this task, since provides human readable descriptions in various languages and does not require a fully fledged scheduler to provide them. Supports multiple cron formats. Below a code snippet from the docs:

//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"

Solution 3

In Java, have a look into cron4j http://www.sauronsoftware.it/projects/cron4j/

You will find the parser you need but then you have to write your code to print the string as you need it. Start by creating a SchedulingPattern object:

new SchedulingPattern("0 30 10-13 ? * 1,2,5")