Cron Expression Parser

Overview

This project is a Java-based Cron Expression Parser, which parses and validates cron expressions according to standard cron syntax. The parser is capable of interpreting cron fields, including ranges, steps, wildcards, and lists, and provides detailed outputs of the parsed cron schedule.

Project Structure

• CronParser.java: The main entry point for the application. It parses the input cron expression and prints the parsed schedule.
• CronExpression.java: Represents the parsed cron expression and contains logic for managing and displaying the parsed output.
• CronField.java: Represents a single field in a cron expression (e.g., minutes, hours). It holds the parsed values for that field.
• CronFieldHandler.java: Contains logic for parsing and validating cron fields. This includes handling wildcards (*), lists (e.g., 1,2,3), ranges (e.g., 1-5), and steps (e.g., */2).

Dependencies

This project uses the following dependencies:

• JUnit 5: Used for unit testing. Ensure that your pom.xml includes the JUnit 5 dependency:

  <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-engine</artifactId>
      <version>5.9.3</version>
      <scope>test</scope>
  </dependency>
  

Getting Started

Download the jar

You can download the jar file from cron-parser.jar

Or you can follow the below steps to install the cron parser.

Prerequisites

• Java Version: 17
• Maven Version: 3.9.8

Installation

To get started with the cron-parser project, follow these steps:

1. Clone the repository:

   git clone https://github.com/yourusername/cron-parser.git

   cd cron-parser

2. Build the project using Maven:

   mvn clean install

This will create a jar file in the target directory.

Usage

The cron-parser application allows you to parse cron expressions. Provide a valid cron expression as a string argument when running the program. The cron expression must consist of five fields representing:

• Minutes (0 - 59)
• Hours (0 - 23)
• Day of the Month (1 - 31)
• Month (1 - 12)
• Day of the Week (1 - 7)
• Command to execute

The program will output each field's parsed values, formatted for easy reading.

Example

Navigate to the target directory and run this command:

java -jar cronparser-1.0-SNAPSHOT.jar "*/15 0 15-27/2 * 1-5 /usr/bin/find"

Or run the downloaded jar from it's location

java -jar cron-parser.jar "*/15 0 15-27/2 * 1-5 /usr/bin/find"

Would output the parsed Cron Expression in the below format

minute        0 10 20 30 40 50
hour          0
day of month  15 17 19 21 23 25 27
month         1 2 3 4 5 6 7 8 9 10 11 12
day of week   2 3 4 5
command       /usr/bin/find

Running Tests

To run the unit tests for this project, use the following Maven command:

mvn test

This will execute all the tests and provide a summary of the test results.