I'm working on Java web application which requires running certain task (mysql query) once a day. What is the best way to do such thing in Java?
I saw something like Quartz but I'm not sure if it is ok for job like this. With quick review it looks like quartz requires initialization. Can it be done with web application? What about downtimes?
quartz is a great solution (the documentation tells you how to start it in a servlet container). it's also a very popular solution so there is plenty of documentation online.
if you are running within a full j2ee container, there is a built in timer service.
Related
I am new to J2EE and i am working on couple of tasks. one of them is :
I have a web application that works like a reporting toolbox hosted by Apache tomcat 7, I need a heavy weight job to be scheduled to run every hour or other intervals, I googled and find Apache Sling that is kind of separate application server for content-centeric applications. I want to know if there is other solution could be done Apache tomcat or not ?
also its important that solution would be standard and reliable.
There's the ScheduledExecutorService which is part of the standard java api. See the new*Schedule* factory methods in Executors.
For a more heavyweight / configurable option there's Quartz. One of Quartz' nice features is it's support for cron expressions
You can also use Spring Batch. Here's a link that can help you understand this framework.
http://projects.spring.io/spring-batch/faq.html
In case none of the packages work for you one option would be to implement a ServletContextListener. It is an object that is launched when your site goes online. The only problem is that you have to manage all the scheduling.
I am interested in understanding "best practice" for the use of application server (for example Glassfish). I have a medium size application that consists of various components that consume and source web services. These components are hosted in a Glassfish environment.
I now have a requirement for a simple scheduled function that copies data from one database to another. That is, it requires no web type functionality. It could easily be built as a simple application (say around Quartz) and deployed in the same Glassfish server with the other components. I understand that this is a simple question, however is this a "reasonable" approach or should it really be a stand alone application running independently from an application server? I guess the more general question is "What are appropriate uses for an application server and what are not?"
It could just be a shell script called from cron...
Seriously, not a very good use of an app server UNLESS you're going to get some sort of monitoring or load distribution out of it. But it sounds like this is really just a batch job in which case you should do the easy thing and just write a script or a simple app with a main method that you either call from cron (or something similar) or run from the command line with some sort of embedded timer (or a sleeping thread).
I need to develop a game server that will run periodically (e.g., triggered by a CRON job every five minutes or hour as appropriate). Once started up, the server will access all of the current game state (fetched through REST from the game's data servers (Stackmob, Parse or similar), do the processing of player actions, and then POST the results back to the data server. In other words, it will be doing a lot of HTTP requests, but does not itself necessarily need to be a web service.
I've been considering multiple ways of developing this.
I do not feel for setting up a server myself, so I need to find a service to run this on that permits the workflow I would like.
The game engine is Java, so something that works neatly with that.
Will need to GET and POST data files, so access to static files would be needed.
Most of the services that exist which provide something similar to what I require are directed at web services - which generally means that one needs to jump through some hoops to get things to work.
Google App Engine, for instance, would require that I implement this using backends (since the game server could potentially run for more than 60 seconds), and isn't particularly happy with the idea of static files.
Amazon EC2 would seem easier to develop on (again by building a web service frontend, of course), but there seems to be relatively poor support for CRON.
Generally speaking, it feels like I want to shoot some sparrows with a slingshot, but all the services are offering me cannons. Are there any alternative platforms/frameworks beyond the big two mentioned above that would be suitable for something like this?
You could try Heroku. They support Java. If you created a project that used a single worker dyno then the hosting would be free (see link).
The process would be running continuously, so you might want use a Timer for periodic execution. You could also use Quartz, but it might be overkill.
Edit:
Here's some links that might help get started:
Running non-web Java processes on Heroku
Heroku Java quickstart - this is for a web app ('web dyno') rather than a 'worker dyno', but it may help.
java.herokuapp.com has links to some example projects (again web apps rather than workers)
How about using EC2, but rather than putting the scheduler in the instance (which won't work because the instance can go away at any time), putting it in AWS? Like this guy:
http://alestic.com/2011/11/ec2-schedule-instance
Alternatively, if you manage your EC2 instances through Ylastic, it looks even easier:
http://blog.ylastic.com/scheduling-tasks-on-the-aws-cloud
Although you'll have to pay for Ylastic as well as EC2, i imagine.
I found a nifty way of writing something like this in Groovy with Maven. You can write a multithreaded Groovy script to pull the stats, do the updates, etc. and then have maven's assembly plugin assemble the whole thing into a self-contained, executable jar file that can be called by a CRON job. One nice thing about Groovy is that its syntax allows you to do this:
def google = "http://google.com".toURL().text
which will turn the string into a URL and handle all of the details of turning the URL into a HTTPURLConnection and getting the raw text.
You could develop the app as a standalone Java program first and then worry about where to deploy it later.
To develop the app you could write a simple Java program that uses HtmlUnit to talk to the external web services. The job could be internally started via Quartz. If you really wanted to start the job externally via CRON, you could have CRON run the app, passing in args. The app would then run and exit.
Alternatively, you could have the app always running and have cron run a bash script that triggers the job in some way.
Essentially, all you need to deploy is a Unix machine so you could use AWS.
I'm a long-time client-side (Swing) developer and I operated pretty much by myself in the same job for a long time. Working from home in a vacuum, I was pretty much completely isolated from the community. I recently took a position as a server-side Java guy for a startup, and I'm learning a ton of stuff but I'm the only Java person and am pretty much on my own again. Having never done server-side Java before, so much of this stuff is completely new and I feel like I have no idea what the normal best-practices are, or I don't have an intuitive feel for what tools to use for what jobs. I keep reading and reading various Internet sources (SO is awesome!) trying to bulk up my knowledge, but some things seem hard to search for because they don't have any obvious keywords. Hopefully some of you gurus here can point me in the right direction.
I'm in charge of implementing our backend REST service, which for now supports our website and an iPhone app. We're doing a social media site, eventually with many different clients. Currently the only clients of the service are our own website and our own iPhone app. I'm using Jersey, Spring, Tomcat, and RDS (Amazon's MySQL) on Amazon's EC2 platform. Our media storage is via S3. I've picked up all of these things pretty quickly and so far so good -- things are working fine with the website and the iPhone app. Cool.
Our next step is adding some long-running server-side processing. This processing is basically CPU-intensive stuff that doesn't involve any communication until it's done. I'm trying to figure out what the best way to handle this is. I'm thinking of using Amazon's SQS to queue up jobs in response to the REST events that should trigger them, but I can't figure out how I should handle the dequeuing and processing. I know I need some threads somewhere that take jobs off the SQS queue and process them, and then tell the REST service that the job is done. But where do these threads live?
In a plain "java -jar jobconsumer.jar" process on another EC2 instance that starts a small thread pool. Maybe use Spring to wire up this piece and start it running?
In a webapp deployed in a container like Tomcat on another EC2 instance? I don't really know what benefits I would get from this, but somehow running in a container like this seems more stable? Does this sort of container even really support long-running processing loops, or is it just good at responding to HTTP events?
Now that I write it out like that, I don't really see why I would want to use a container. It just seems like an over-complication. However, the Java community seems so centered on these types of containerized, "managed" environments that to not use a container seems somehow wrong. I feel like maybe I'm not understanding what some of the major benefits of these containers are? I mean, beyond the obvious benefits of the web-facing Servlet and JSP specs. Would any of the functionality of those specs help me out with something like this?
For a regular Java web app, you almost certainly want to be using one of the Servlet containers such as Tomcat - it takes care of accepting connections, parsing and serialising HTTP messages, JSPs, SSL, authentication, etc for you.
For a non-web app, the argument for using Tomcat (or similar) is weaker, but there are a few reasons to still consider it:
straightforward to add JSPs for querying and managing the app or add a web API in future
easy distribution of releases (one .war vs. an unholy mess of jars and config files)
hot deployment (although I've yet to see anyone using this for anything serious)
In terms of long-running processing loops, Servlet containers don't help you out beyond notifying your ServletContextListener when the app starts, so you can kick off any long-running tasks.
It's worth noting that if you're already using Spring, it's relatively easy to switch from a stand-alone app to a container using ContextLoaderListener, so it shouldn't be a problem if you decide later that you need the web stuff.
We recently faced a similar question, as we are hosting a large distributed service on EC2.
In short, we are very happy with Jetty 7 as a container. We use it for our user-facing-www, public-api, and internal-backend-api services. In some cases we use it for non-api services such as a workqueue, simply to expose a bit of status & health info for our monitoring.
The great thing about Jetty (any version) is that it can be configured in ~5 lines of code, with zero external config files etc. It's not a container specifically, but an http server that you can embed.
We use Guice for dependency injection, which also favors config-file-less implementations.
Long lived Java processes are nothing to worry about - you basically bring up your servers / threads / threadpools in your main method and don't call System.exit until you want to shutdown explicitly.
I want to run a Java program on a specific date.
I am developing a J2EE application that allows you to schedule Selenium test launch (JUnit) on a specified date..
Are there any solutions to do this? can you point me to technology that can help me to do this?
any help is appreciated:)
thanks for your help
You provided very little information. You can schedule launch in scheduler of your operating system (like cron in Linux), or you can run a task from within your Java process, if the process is constantly running. For this see Quartz Scheduler.
Not knowing enough details, I would recommend using Quartz. You can see an example of using it here.
You could use crond or Windows Task Manager.
If you have a Java process running from now to the time it needs to start, look at Quartz.
If you need to have a Java process started from nothing, you must ask your operating system to invoke it for you. For Linux check the "at" command.
Cron on Unix, and Cron for NT on WindowsNT platforms (XP-Windows 7, Windows Server 4.0+).
Why reinvent the wheel?
If you want to create and package modular java server-side tasks (that you can then schedule in any particular java scheduler of your choice) check out the open source project called soafaces. Let's you create modular java Tasklets and also give them web based GUI customizer (customizer part is optional and based on google gwt).
Scheduling can be implemented in many ways, it is also bit IO intensive, so if needed u might want to use non-java solutions
However you want to have java solutions may be below links should help you
Spring Way : https://spring.io/guides/gs/scheduling-tasks/ and https://dzone.com/articles/schedulers-in-java-and-spring
Non Spring solution: https://github.com/knowm/Sundial