Schedule Jobs in Java using Quartz (Java Job scheduling tutorial)

-

Schedule Jobs in Java using Quartz (Java Job scheduling tutorial)

How to schedule Jobs in Java using Quartz (Java Job scheduling tutorial)
This tutorial is intended for Users who are looking to automate job scheduling in Java using Quartz. For example, if you would like to run a particular Java program at a particular point of time and date (and at regular frequencies) automatically, you can use the Quartz API to achieve this.
I will provide a simple example that covers the basics of the Quartz API to perform the scheduling.
Quartz API has the following basic objects.



> SchedulerFactory

> Scheduler

> JobDetail

> Trigger.

If you are not using Maven(or don’t know what Maven is), download the Quartz API from www.quartzscheduler.org and include it in your application’s build path. Btw, I strongly recommend you to start using Maven for your projects if you haven’t already. Off topic, but it is a wonderful dependency management tool (among various other features)




The concept is that you create a Scheduler object using the SchedulerFactory (Factory pattern if you know what I mean. I will show the related code below). And then you create a JobDetail object(by assigning the job a name and a group). Finally, you create a Trigger object that tells the scheduler on when to run the Job.



The trigger schedule can be set using CRON. If you are not sure what CRON is, it is just a expression (which is essentially a string) that tells the second/minute/hour/day of month/month/day of week/year in a regex format. The first 6 fields are mandatory and the last one(year) is optional.



A cron expression is a string comprised of 6 or 7 fields(explained above) separated by white space. Fields can contain any of the allowed values, along with various combinations of the allowed special characters for that field.



Just look at the following expression.



10 * * * * ?



This means that on the 10th second(1st field - 10)of every minute(2nd field - *) of every hour (3rd field - *)of every day(4th field - *)  of every month (5th field - *), the job will be run. The 6th field was marked as ? as there is no specific useful value for that. I mean if we are running the job everyday, there is no point in mentioning it to run on Sun/Mon/Tue etc. Also, if in another CRON expression we want to run on the 15th of every month and we don’t care what day of the week it is (Sun/Mon etc.), we can mark the 6th field as ?. I think you get the idea. The 7th field is the year, which is an optional field, which I haven’t used in the above expression. Another example:



0 0 0 1 1 ? *



On the 0th second of the 0th minute of the 0th hour of the 1st day of the 1st month of each year, do something. Like partying for a new year?



Ok, enough of CRON. There are a lot of other ways to use/customize CRON, which you can read in the related links at the end of the post.  Now back to the Quartz scheduler program.


Create a new Java class named QuartzTesting. This has to implement the Job interface, and thereby the execute method. Once the below program is run, the code in the execute method will be invoked at the regular frequency specified as per the CRON expression.





Now, if you compile and run the above program, you will see a Java process running in your task manager. You should the Sysout at the intervals specified as per CRON (on the 10th  second of each minute in the above example. Please note that you see Sysouts every one minute and not every 10 seconds. If you want Sysouts every 10 seconds change the CRON expression to */10 * * * * ? )



If you were wondering what the name and Group are for the JobDetail/Trigger objects, they are used to identify the jobs if you have multiple jobs/triggers. In those multiple job scenarios, you can refer to the particular jobs using their names. Something like,

 

//Delete if the job already exists and then schedule the job
          sched.deleteJob(“Sending Job”, “Send Group”);
References/Useful links:



  1. www.quartzscheduler.org
  2. http://oreilly.com/pub/a/java/archive/quartz.html?page=1
  3. http://www.quartz-scheduler.org/docs/tutorials/crontrigger.html

  thank you ..

  1. http://runningexample.blogspot.in

Comments

Post a Comment

Popular posts from this blog

Java LinkedList class in Collection

-
Image
Java LinkedList class in Collection --  LinkedList class uses doubly linked list to store the elements and data. It provide a linked-list data structure.get free coins thetechieking --  It inherits the AbstractList class and implements List and Deque interfaces in java. --  LinkedList class is non synchronized. --  LinkedList class follow insertion order.  --  LinkedList class can allow duplicate elements to store data. --  manipulation is faster than ArrayList because no shifting needs. Declaration of LinkedList class in java : -- public class LinkedList<E> extends AbstractSequentialList<E>    implements List<E>, Deque<E>, Cloneable, Serializable   Constructors of Java LinkedList :  LinkedList()   LinkedList(Collection c) Methods of LinkedList class : 1) boolean add ( Object element ) : -- It appends the element to the end of the list. 2) void add ( int index, Object element ) : -- It inserts the element at the position
Read more

Java ArrayList class in collections

-
Image
Java ArrayList class in collections --  ArrayList class uses a dynamic array for storing the elements. It inherits AbstractList class and implements List interface in java.  --  ArrayList class can allows random access because array works at  the index basis.  --  ArrayList is non synchronized class in java. --  ArrayList class maintains insertion order to data --  ArrayList can contain duplicate elements. --  manipulation is slow in ArrayList class because a lot of shifting      needs to operation with data.   ArrayList class have three Constructor.    1) ArrayList ( )   2) ArrayList ( Collection c )   3) ArrayList ( int capacity )    Some Methods of  ArrayList class   1) void add ( int index, Object element )    -   insert the specified element at the specified position index in a list.   2) boolean addAll ( Collection c )    -  used to append all of the elements in the specified collection to the       end of this
Read more

Constructors in Java

-
Image
Constructors in Java. -- A constructor is a special method of function  that is used to   initialize an object in java. --  every class has a constructor by default. --  compiler build a default constructor for that class. --  constructor are executed at time of object creation of class.  --  there are no return type in java constructor --  An interface cannot have the constructor in java. --  Constructors cannot be private modifire. --  Constructors name must be similar to that of the class name.   There are 2 type of constructor in Java :     1) Default Constructor.  2) Parameterized constructor.     1) Default Constructor. --  A java constructor that has no parameter is known as default constructor. thats build by compiler. --  if we write a constructor with parameter or non-parameter then compiler does not create default constructor. example of default constructor : class JavaConstructor {        JavaConstructo
Read more