Monday, August 26, 2013

How to create web-app with Quartz Scheduler and logging

I sometimes help out users in Quartz Scheduler forums. Once in a while some one would ask how can he/she setup the Quartz inside a web application. This is actualy a fairly simple thing to do. The library already comes with a ServletContextListener that you can use to start a Scheduler. I will show you a simple webapp example here.

First create a Maven pom.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation=
        "http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>quartz-web-demo</groupId>
    <artifactId>quartz-web-demo</artifactId>
    <packaging>war</packaging>
    <version>1.0-SANPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz</artifactId>
            <version>2.2.0</version>
        </dependency>
    </dependencies>

</project>

Then you need to create a src/main/webapp/META-INF/web.xml file.

<?xml version="1.0" encoding="UTF-8"?>
 <web-app version="2.5"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation=
        "http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

     <context-param>
         <param-name>quartz:config-file</param-name>
         <param-value>quartz.properties</param-value>
     </context-param>
     <context-param>
         <param-name>quartz:shutdown-on-unload</param-name>
         <param-value>true</param-value>
     </context-param>
     <context-param>
         <param-name>quartz:wait-on-shutdown</param-name>
         <param-value>true</param-value>
     </context-param>
     <context-param>
         <param-name>quartz:start-on-load</param-name>
         <param-value>true</param-value>
     </context-param>

     <listener>
         <listener-class>org.quartz.ee.servlet.QuartzInitializerListener</listener-class>
     </listener>

 </web-app>

And lastly, you need a src/main/resources/quartz.properties config file for Scheduler.

# Main Quartz configuration
org.quartz.scheduler.skipUpdateCheck = true
org.quartz.scheduler.instanceName = MyQuartzScheduler
org.quartz.scheduler.jobFactory.class = org.quartz.simpl.SimpleJobFactory
org.quartz.threadPool.class = org.quartz.simpl.SimpleThreadPool
org.quartz.threadPool.threadCount = 5

You may configure many other things with Quartz, but above should get you started as in In-Memory scheduler.

Now you should able to compile and run it.

bash> mvn compile
bash> mvn org.apache.tomcat.maven:tomcat7-maven-plugin:2.1:run -Dmaven.tomcat.port=8081

How to configure logging for Quartz Scheduler

Another frequently asked question is how do they setup logging and see the DEBUG level messages. The Quartz Schedulers uses SLF4J, so you have many loggers options to choose. I will show you how to setup Log4j for example below.

First, add this to your pom.xml

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.5</version>
        </dependency>

Then add src/main/resources/log4j.properties file to show messages onto STDOUT.

log4j.rootLogger=INFO, stdout
log4j.logger.org.quartz=DEBUG
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

Restart your web application on command line, and now you should see all the DEBUG level logging messages coming from Quartz library.

With everything running, your next question might be asking how do you access the scheduler from your web application? Well, when the scheduler is created by the servlet context listener, it is stored inside the web app’s ServletContext space with org.quartz.impl.StdSchedulerFactory.KEY key. So you may retrieve it and use it in your own Servlet like this:

public class YourServlet extends HttpServlet {
    public init(ServletConfig cfg) {
        String key = "org.quartz.impl.StdSchedulerFactory.KEY";
        ServletContext servletContext = cfg.getServletContext();
        StdSchedulerFactory factory = (StdSchedulerFactory) servletContext.getAttribute(key);
        Scheduler quartzScheduler = factory.getScheduler("MyQuartzScheduler");
        // TODO use quartzScheduler here.
    }
}

Now you are on your way to build your next scheduling application!

Have fun!