Java – Quartz Scheduler using JDBC JobStore

javajob-schedulingquartz-schedulerstruts2

For the first time i stored the jobs and scheduled them using crontrigger with the below code.

package com.generalsentiment.test.quartz;

import static org.quartz.CronScheduleBuilder.cronSchedule;
import static org.quartz.JobBuilder.newJob;
import static org.quartz.TriggerBuilder.newTrigger;

import java.util.Date;
import java.util.Properties;

import org.quartz.CronTrigger;
import org.quartz.JobDetail;
import org.quartz.Scheduler;
import org.quartz.SchedulerFactory;
import org.quartz.SchedulerMetaData;
import org.quartz.impl.StdSchedulerFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class CronTriggerExample {

    public void run() throws Exception {
        Logger log = LoggerFactory.getLogger(CronTriggerExample.class);

        System.out.println("------- Initializing -------------------");

        Xml config = new Xml("src/hibernate.cfg.xml", "hibernate-configuration");

        Properties prop = new Properties();
        prop.setProperty("org.quartz.scheduler.instanceName", "ALARM_SCHEDULER");
        prop.setProperty("org.quartz.threadPool.class",   
                        "org.quartz.simpl.SimpleThreadPool");
        prop.setProperty("org.quartz.threadPool.threadCount", "4");

        prop.setProperty("org.quartz.threadPool
                        .threadsInheritContextClassLoaderOfInitializingThread", "true");

        prop.setProperty("org.quartz.jobStore.class", 
                          "org.quartz.impl.jdbcjobstore.JobStoreTX");
        prop.setProperty("org.quartz.jobStore.driverDelegateClass", 
                          "org.quartz.impl.jdbcjobstore.StdJDBCDelegate");
        prop.setProperty("org.quartz.jobStore.dataSource", "tasksDataStore");
        prop.setProperty("org.quartz.jobStore.tablePrefix", "QRTZ_");
        prop.setProperty("org.quartz.jobStore.misfireThreshold", "60000");
        prop.setProperty("org.quartz.jobStore.isClustered", "false");

        prop.setProperty("org.quartz.dataSource.tasksDataStore.driver", 
              config.child("session-factory").children("property").get(1).content());
        prop.setProperty("org.quartz.dataSource.tasksDataStore.URL", config.child("session-
             factory").children("property").get(2).content());
        prop.setProperty("org.quartz.dataSource.tasksDataStore.user", config.child("session-
             factory").children("property").get(3).content());
        prop.setProperty("org.quartz.dataSource.tasksDataStore.password", 
             config.child("session-factory").children("property").get(4).content());
        prop.setProperty("org.quartz.dataSource.tasksDataStore.maxConnections", "20");

        // First we must get a reference to a scheduler
        SchedulerFactory sf = new StdSchedulerFactory(prop);
        Scheduler sched = sf.getScheduler();

        System.out.println("------- Initialization Complete --------");

        System.out.println("------- Scheduling Jobs ----------------");

        // jobs can be scheduled before sched.start() has been called

        // job 1 will run exactly at 12:55 daily
        JobDetail job = newJob(SimpleJob.class).withIdentity("job2", "group2").build();

        CronTrigger trigger = newTrigger().withIdentity("trigger2", "group2")
                                          .withSchedule(cronSchedule("00 15 15 * * 
                                                         ?")).build();

        Date ft = sched.scheduleJob(job, trigger);
        System.out.println(sched.getSchedulerName());
        System.out.println(job.getKey() + " has been scheduled to run at: " + ft
                + " and repeat based on expression: "
                + trigger.getCronExpression());

        System.out.println("------- Starting Scheduler ----------------");

        /*
         * All of the jobs have been added to the scheduler, but none of the
         * jobs will run until the scheduler has been started. If you have
         * multiple jobs performing multiple tasks, then its recommended to
         * write it in separate classes, like SimpleJob.class writes
         * organization members to file.
         */
        sched.start();

        System.out.println("------- Started Scheduler -----------------");

        System.out.println("------- Waiting five minutes... ------------");
        try {
            // wait five minutes to show jobs
            Thread.sleep(300L * 1000L);
            // executing...
        } catch (Exception e) {
        }

        System.out.println("------- Shutting Down ---------------------");

        sched.shutdown(true);

        System.out.println("------- Shutdown Complete -----------------");

        SchedulerMetaData metaData = sched.getMetaData();


        System.out.println("Executed " + metaData.getNumberOfJobsExecuted() + " jobs.");

    }

    public static void main(String[] args) throws Exception {

        CronTriggerExample example = new CronTriggerExample();
        example.run();
    }
    }

And the details are stored in Tables – QRTZ_CRON_TRIGGERS, QRTZ_JOB_DETAILS & QRTZ_TRIGGERS

My doubt is How to schedule the jobs that are stored in DB. How to display the list of jobs in a jsp page & how to trigger them automatically.
Ours is a struts2 application with Hibernate3 ORM. I am trying to initialize the quartz scheduler when the application loads. But am unable to.

Best Answer

Date ft = sched.scheduleJob(job, trigger);

When this is called, your job would be scheduled for the next fire time. The scheduled job would stored in the appropriate DB tables. To Display the list of jobs on a jsp, you should persist you job key as well as custom description of what your job entails to another DB table so that during retrieval you can retrieve this custom description as well as data Quartz persist into its own tables. Triggering this jobs automatically is something Quartz handles for you. Once the crone expression is set to what is desired and your Job class implements org.quartz.Job, Quartz would run the execute() method at your desired next fire time

Related Solutions

Java – How to create an executable JAR with dependencies using Maven

<build>
  <plugins>
    <plugin>
      <artifactId>maven-assembly-plugin</artifactId>
      <configuration>
        <archive>
          <manifest>
            <mainClass>fully.qualified.MainClass</mainClass>
          </manifest>
        </archive>
        <descriptorRefs>
          <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
      </configuration>
    </plugin>
  </plugins>
</build>

and you run it with

mvn clean compile assembly:single

Compile goal should be added before assembly:single or otherwise the code on your own project is not included.

See more details in comments.

Commonly this goal is tied to a build phase to execute automatically. This ensures the JAR is built when executing mvn install or performing a deployment/release.

<plugin>
  <artifactId>maven-assembly-plugin</artifactId>
  <configuration>
    <archive>
      <manifest>
        <mainClass>fully.qualified.MainClass</mainClass>
      </manifest>
    </archive>
    <descriptorRefs>
      <descriptorRef>jar-with-dependencies</descriptorRef>
    </descriptorRefs>
  </configuration>
  <executions>
    <execution>
      <id>make-assembly</id> <!-- this is used for inheritance merges -->
      <phase>package</phase> <!-- bind to the packaging phase -->
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Java – How to avoid Java code in JSP files, using JSP 2

The use of scriptlets (those <% %> things) in JSP is indeed highly discouraged since the birth of taglibs (like JSTL) and EL (Expression Language, those ${} things) way back in 2001.

The major disadvantages of scriptlets are:

Reusability: you can't reuse scriptlets.
Replaceability: you can't make scriptlets abstract.
OO-ability: you can't make use of inheritance/composition.
Debuggability: if scriptlet throws an exception halfway, all you get is a blank page.
Testability: scriptlets are not unit-testable.
Maintainability: per saldo more time is needed to maintain mingled/cluttered/duplicated code logic.

~~Sun~~ Oracle itself also recommends in the JSP coding conventions to avoid use of scriptlets whenever the same functionality is possible by (tag) classes. Here are several cites of relevance:

From JSP 1.2 Specification, it is highly recommended that the JSP Standard Tag Library (JSTL) be used in your web application to help reduce the need for JSP scriptlets in your pages. Pages that use JSTL are, in general, easier to read and maintain.

...

Where possible, avoid JSP scriptlets whenever tag libraries provide equivalent functionality. This makes pages easier to read and maintain, helps to separate business logic from presentation logic, and will make your pages easier to evolve into JSP 2.0-style pages (JSP 2.0 Specification supports but de-emphasizes the use of scriptlets).

...

In the spirit of adopting the model-view-controller (MVC) design pattern to reduce coupling between the presentation tier from the business logic, JSP scriptlets should not be used for writing business logic. Rather, JSP scriptlets are used if necessary to transform data (also called "value objects") returned from processing the client's requests into a proper client-ready format. Even then, this would be better done with a front controller servlet or a custom tag.

How to replace scriptlets entirely depends on the sole purpose of the code/logic. More than often this code is to be placed in a fullworthy Java class:

If you want to invoke the same Java code on every request, less-or-more regardless of the requested page, e.g. checking if a user is logged in, then implement a filter and write code accordingly in doFilter() method. E.g.:

  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
      if (((HttpServletRequest) request).getSession().getAttribute("user") == null) {
          ((HttpServletResponse) response).sendRedirect("login"); // Not logged in, redirect to login page.
      } else {
          chain.doFilter(request, response); // Logged in, just continue request.
      }
  }

When mapped on an appropriate <url-pattern> covering the JSP pages of interest, then you don't need to copypaste the same piece of code overall JSP pages.

If you want to invoke some Java code to process a GET request, e.g. preloading some list from a database to display in some table, if necessary based on some query parameters, then implement a servlet and write code accordingly in doGet() method. E.g.:
```
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      try {
          List<Product> products = productService.list(); // Obtain all products.
          request.setAttribute("products", products); // Store products in request scope.
          request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response); // Forward to JSP page to display them in a HTML table.
      } catch (SQLException e) {
          throw new ServletException("Retrieving products failed!", e);
      }
  }
```
This way dealing with exceptions is easier. The DB is not accessed in the midst of JSP rendering, but far before the JSP is been displayed. You still have the possibility to change the response whenever the DB access throws an exception. In the above example, the default error 500 page will be displayed which you can anyway customize by an <error-page> in web.xml.

If you want to invoke some Java code to process a POST request, such as gathering data from a submitted HTML form and doing some business stuff with it (conversion, validation, saving in DB, etcetera), then implement a servlet and write code accordingly in doPost() method. E.g.:

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      String username = request.getParameter("username");
      String password = request.getParameter("password");
      User user = userService.find(username, password);

      if (user != null) {
          request.getSession().setAttribute("user", user); // Login user.
          response.sendRedirect("home"); // Redirect to home page.
      } else {
          request.setAttribute("message", "Unknown username/password. Please retry."); // Store error message in request scope.
          request.getRequestDispatcher("/WEB-INF/login.jsp").forward(request, response); // Forward to JSP page to redisplay login form with error.
      }
  }

This way dealing with different result page destinations is easier: redisplaying the form with validation errors in case of an error (in this particular example you can redisplay it using ${message} in EL), or just taking to the desired target page in case of success.

If you want to invoke some Java code to control the execution plan and/or the destination of the request and the response, then implement a servlet according to the MVC's Front Controller Pattern. E.g.:

  protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      try {
          Action action = ActionFactory.getAction(request);
          String view = action.execute(request, response);

          if (view.equals(request.getPathInfo().substring(1)) {
              request.getRequestDispatcher("/WEB-INF/" + view + ".jsp").forward(request, response);
          } else {
              response.sendRedirect(view);
          }
      } catch (Exception e) {
          throw new ServletException("Executing action failed.", e);
      }
  }

Or just adopt an MVC framework like JSF, Spring MVC, Wicket, etc so that you end up with just a JSP/Facelets page and a JavaBean class without the need for a custom servlet.

If you want to invoke some Java code to control the flow inside a JSP page, then you need to grab an (existing) flow control taglib like JSTL core. E.g. displaying List<Product> in a table:
```
  <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
  ...
  <table>
      <c:forEach items="${products}" var="product">
          <tr>
              <td>${product.name}</td>
              <td>${product.description}</td>
              <td>${product.price}</td>
          </tr>
      </c:forEach>
  </table>
```
With XML-style tags which fit nicely among all that HTML, the code is better readable (and thus better maintainable) than a bunch of scriptlets with various opening and closing braces ("Where the heck does this closing brace belong to?"). An easy aid is to configure your web application to throw an exception whenever scriptlets are still been used by adding the following piece to web.xml:
```
  <jsp-config>
      <jsp-property-group>
          <url-pattern>*.jsp</url-pattern>
          <scripting-invalid>true</scripting-invalid>
      </jsp-property-group>
  </jsp-config>
```
In Facelets, the successor of JSP, which is part of the Java EE provided MVC framework JSF, it is already not possible to use scriptlets. This way you're automatically forced to do things "the right way".
If you want to invoke some Java code to access and display "backend" data inside a JSP page, then you need to use EL (Expression Language), those ${} things. E.g. redisplaying submitted input values:
```
  <input type="text" name="foo" value="${param.foo}" />
```
The ${param.foo} displays the outcome of request.getParameter("foo").
If you want to invoke some utility Java code directly in the JSP page (typically public static methods), then you need to define them as EL functions. There's a standard functions taglib in JSTL, but you can also easily create functions yourself. Here's an example how JSTL fn:escapeXml is useful to prevent XSS attacks.
```
  <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
  ...
  <input type="text" name="foo" value="${fn:escapeXml(param.foo)}" />
```
Note that the XSS sensitivity is in no way specifically related to Java/JSP/JSTL/EL/whatever, this problem needs to be taken into account in every web application you develop. The problem of scriptlets is that it provides no way of builtin preventions, at least not using the standard Java API. JSP's successor Facelets has already implicit HTML escaping, so you don't need to worry about XSS holes in Facelets.

Best Answer

Related Solutions

Java – How to create an executable JAR with dependencies using Maven

Java – How to avoid Java code in JSP files, using JSP 2

See also:

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