Can anyone please suggest me the best approach for my requirement? I need to automatically update the table value after some specified time, using Java and MySQL as the database.
Using Quartz scheduler you can achieve this. You need to create one job and run that job at the required time so that it will fetch the data from the database and according to that you will do what's needed.
Quartz Scheduler Tutorial
Create a timer in Java.
Add a task to timer that updates value to MySQL.
Start timer
Example of Java Timer API: here
Related
I have a job done with the quartz plugin, but I would like to run it only if my User table contains users with active status.
Thank you
I have a job done with the quartz plugin, but I would like to run it
only if my User table contains users with active status.
There isn't enough information here to know for sure what the right thing to do is but one thing to consider is you can schedule the Quartz job to run at whatever frequency you like and have the job query the database regarding user active status, and then the job can react accordingly.
I think what you want is a webhook; after a put/post/delete (ie idempotent call), you call another endpoint.
I have several datetime column in my MySQL DB. I want to trigger a java function when the date is reached. At worst, trigger a MySQL function can do the job as well. How to have a trigger datetime based on MySQL without doing cron job on every minute ?
Even a trigger wouldn't do the job, there must be a process to check (in your case if the date was reached)
Like Thomas said job or a task (CRON) that sets the trigger or an application to do what you wish with the database.
It is not ideal to do this in database, but if no better choice, you can achieve it by creating a MySQL event, which is a scheduled task.
You need to add a insert and/or update trigger to the database table and create the event based on the datetime value of the column
You can create the event in the way that drops itself after it is executed at the specified time.
There are few tables that quartz scheduler uses for scheduling jobs and to identify which job is running currently. It uses the following tables :
qrtz_fired_triggers
qrtz_simple_triggers
qrtz_simprop_triggers
qrtz_cron_triggers
qrtz_blob_triggers
qrtz_triggers
qrtz_job_details
qrtz_calendars
qrtz_paused_trigger_grps
qrtz_locks
qrtz_scheduler_state
So what is the purpose of each of these tables and what does it siginifies?
Thanks in advance.
I had the chance to work on quartz recently. I'm myself not 100% clear on this topic and I'm going to try my best to answer your question from my personal experience.
You must remember this basic flow-
1. Create a job.
2. Create a Trigger.
3. Scheduler(job, trigger)
All the above tables are based on the above 3 steps.
qrtz_triggers is where general information of a trigger is saved.
qrtz_simple_triggers, qrtz_simprop_triggers, qrtz_crons_triggers, qrtz_blob_triggers have a foreign key relation to qrtz_triggers which save those specific details. Ex. Cron has cron expression which is unique to it.
qrtz_job_details is simply the task to be executed.
qrtz_fired_triggers is a log of all the triggers that were fired.
qrtz_paused trigger is to save the information about triggers which are not active.
Calendars are useful for excluding blocks of time from the the trigger’s firing schedule. For instance, you could create a trigger that fires a job every weekday at 9:30 am, but then add a Calendar that excludes all of the business’s holidays. (taken from website. I havent' worked on it)
I honestly haven't worked in qrtz_locks, qrtz_scheduler_sate tables.
Check out this image which I reverse engineered using MySQL workbench.
I can provide some inputs for qrtz_lock and qrtz_scheduler_sate tables:
qrtz_lock stores the value of the instance name executing the job, to avoid the sceanario of multiple nodes executing the same job
qrtz_scheduler_state is for capturing the node state so that if in any case one node gets down or failed to execute one of the job then the other instance running in clustering mode can pick the misfired job.
How to make my java class to continuously read the database in a loop and then send reminders through java mail if there is an entry in the database.
For example,
I have a table called "jobs" which has the columns job_id, epoch_time, email_id.
Here when the epoch_time equals current time, I have to send mail to email_id.
Thanks in advance.
You can use trigger to call a JAVA program you want. Say, you can call a program in AFTER INSERT or BEFORE INSERT. Refer https://docs.oracle.com/database/122/JJDEV/calling-Java-from-database-triggers.htm#JJDEV13286. Hope this suits your scenario.
You Can do it with extending TimerTask to your class. For example Read More about Java TimerTask
Another option is Using Java Timer. Using scheduling method you can schedule your specific task. Example with Java Timer
I have a scenario where I check for a specific value in the Database every 10 seconds or so. And, if the value is YES, then I execute a bunch of shell scripts from a Java application.
Now, the value in database is only updated to YES once in a while depending on the user submitting a job on a web page. Therefore, running a while loop to check for this value in database seems to be a very bad design and I would like to implement a much cleaner approach using listeners (Observer design pattern).
How would such an implementation look like? Any examples I can follow to do this?
Yes there is much better job. So there is something called binlog reader in mysql. Thats how master and slave sync is done in mysql cluster database.
So either you write your own logic over https://github.com/shyiko/mysql-binlog-connector-java which gets all the chane event on table
or use https://github.com/zendesk/maxwell to read events from particular table and whenver any change in value is there check if it matches your condition and excute the script or java application on basis of that instead of running it as a cron.
The general idea is to use DB triggers, register DB listener from Java side and be notified from DB side when some event has happened.
Pls review proposed solutions
How to implement a db listener in Java