JBPM3.2与Spring结合时任务调度的实现

Jbpm3.1.x的时候,如果我们要实现Jbpm与Spring结合使用需要借助于SpringModule中spring-modules-jbpm31.jar来实现。目前Jbpm的最新版本是3.2.1，对于这一版本如果我们要实现其与Spring结合使用，同样我们也可以借助SpringModule中spring-modules-jbpm31.jar来实现。
首先我们需要下载spring-modules-0.8工程包文件(下载地址：http://springmodules.dev.java.net)，下载后我们只需要工程包里的spring-modules-jbpm31.jar把它放在我们Web应该的WEB-INF/lib目录下，我们知道该包是为Jbpm3.1准备的，但在Jbpm3.2中我们还是可以借助该包实现与Spring结合。
打开WEB应该里的web.xml文件，加上Jbpm3.2任务调试的Servlet，配置信息如下：
<!-- JbpmJobExecutorServlet -->
<servlet>
<servlet-name>JobExecutorServlet</servlet-name>
<servlet-class>
org.jbpm.job.executor.JobExecutorServlet
</servlet-class>
<load-on-startup>3</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>JobExecutorServlet</servlet-name>
<url-pattern>/jobs</url-pattern>
</servlet-mapping>
Jbpm3.2中任务调度的配置和Jbpm3.1.x中任务调度配置方法与原理基本相同。在Jbpm3.1.x中任务调度我们可以认为就是一个后台线程在不停的监听着timer(jbpm_timer表)，如果有需要触发的timer生成了，就按照timer的属性定时或者循环触发它。Jbpm3.1.x中我们是按下面的方法配置任务调度的servlet的：
<servlet>
<servlet-name>SchedulerServlet</servlet-name>
<servlet-class>
org.jbpm.scheduler.impl.SchedulerServlet
</servlet-class>
<init-param>
<param-name>interval</param-name>
<param-value>5000</param-value>
</init-param>
<init-param>
<param-name>historyMaxSize</param-name>
<param-value>50</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>SchedulerServlet</servlet-name>
<url-pattern>/jbpmscheduler</url-pattern>
</servlet-mapping>

在Jbpm3.2中已经取消了jbpm_timer表，取而代之的是jbpm_job表。也就是说我们可以理解成后台有一个线程在不停的监听着jbpm_job表，如果有需要触发的timer生成了，就按照timer的属性定时或者循环触发它。比较一下两个不同版本的的配置3.1.x里用的是org.jbpm.scheduler.impl.SchedulerServlet，而3.2里用的是org.jbpm.job.executor.JobExecutorServlet这是最明显的不同之处，另外关于扫描表的周期值等相关参数3.1.x是直接设置在servlet里，而3.2里则是配置在jbpm.cfg.xml里:
  <bean name="jbpm.job.executor" class="org.jbpm.job.executor.CustomJobExecutor">
    <field name="jbpmConfiguration"><ref bean="jbpmConfiguration" /></field>
    <!--field name="jbpmConfiguration"><ref bean="jbpmConfiguration" /></field-->
    <field name="name"><string value="JbpmJobExector" /></field>
    <field name="nbrOfThreads"><int value="1" /></field>
    <field name="idleInterval"><int value="5000" /></field>
    <field name="maxIdleInterval"><int value="3600000" /></field> <!-- 1 hour -->
    <field name="historyMaxSize"><int value="20" /></field>
    <field name="maxLockTime"><int value="600000" /></field> <!-- 10 minutes -->
    <field name="lockMonitorInterval"><int value="60000" /></field> <!-- 1 minute -->
    <field name="lockBufferTime"><int value="5000" /></field> <!-- 5 seconds -->
  </bean>

到这里为止Jbpm的任务的Servlet配置已经完成了，如果直接使用hibernate.cfg.xml来连接数据库的话那我们上面的配置就够了。如果我们使用Spring，那还有一些工作要完成。接下来要看一下怎么去在Spring中配置Jbpm。
首先我们要在Spring的配置文件里配置好Hibernate的SessionFacotry等相关信息：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
"http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>WEB-INF/configs/jdbc.properties</value>
</list>
</property>
</bean>

<!-- configuration datasource -->

<!—配置数据源-->
<bean id="dataSource"
class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName"
value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>

<!—利用数据源配置Hibernate的SessionFactory -->
<bean id="sessionFactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource">
<ref local="dataSource" />
</property>

<!—-设置Jbpm中cfg.xml文件的映射，这里从jbpm-jpdl.jar里读取cfg.xml文件-->
<property name="mappingJarLocations">
<list>
<value>WEB-INF/lib/jbpm-jpdl.jar</value>
</list>
</property>

<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.MySQL5Dialect
</prop>
<prop key="hibernate.show_sql">false</prop>
<prop key="hibernate.cache.provider_class">org.hibernate.cache.HashtableCacheProvider</prop>
</props>
</property>
</bean>
</beans>
接下来我们要把spring-modules-jbpm31.jar中提供的JbpmConfiguration配置进去：
<!-- jBPM configuration -->
<bean id="jbpmConfiguration"
class="org.springmodules.workflow.jbpm31.LocalJbpmConfigurationFactoryBean">
<property name="sessionFactory" ref="sessionFactory" />
<property name="configuration" value="classpath:jbpm.cfg.xml" />
<property name="createSchema" value="false" />
</bean>

<bean id="jbpmTemplate"
class="org.springmodules.workflow.jbpm31.JbpmTemplate">
<constructor-arg index="0" ref="jbpmConfiguration" />
</bean>
这里我们把spring-modules-jbpm31.jar中提供的JbpmTemplate配置进去，这里需要解释一下JbpmTemplate是在Spring中访问Jbpm相关方法的接口对象，利用JbpmTemplate我们可以快速操作Jbpm里提供的方法接口：
public ProcessInstance findProcessInstance(final Long processInstanceId) {
  return (ProcessInstance) jbpmTemplate.execute(new JbpmCallback() {
     public Object doInJbpm(JbpmContext context) {
      // do something
      ...
      return context.getGraphSession().loadProcessInstance(processInstanceId.longValue());
     }
  });
}
接下来我们可以启动工程测试一下，启动过程中我们发现有异常抛出来，告诉我们说找不到hibernate.cfg.xml文件，同时我们也看到该错误是由org.jbpm.job.executor.JobExecutorServlet该类抛出来的，为了修正该错误我们对其修改如下：
package org.jbpm.job.executor;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collection;
import java.util.Iterator;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.jbpm.JbpmConfiguration;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springmodules.workflow.jbpm31.JbpmTemplate;

public class JobExecutorServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

JbpmConfiguration jbpmConfiguration;
//修改了JobExecutorServlet里获取JbpmConfiguration的方式
public void init() throws ServletException {
JbpmTemplate jbpmTemplate = (JbpmTemplate) WebApplicationContextUtils
.getWebApplicationContext(this.getServletContext()).getBean(
"jbpmTemplate");
jbpmConfiguration = jbpmTemplate.getJbpmConfiguration();
jbpmConfiguration.startJobExecutor();
}

protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body>");
out.println("<h2>JBoss jBPM Scheduler Servlet</h2><hr />");
Collection threads = jbpmConfiguration.getJobExecutor().getThreads()
.values();
Iterator iter = threads.iterator();
while (iter.hasNext()) {
Thread thread = (Thread) iter.next();
out.println("<h4>" + thread.getName() + "</h4>");
out.println("<b>isAlive</b>:" + thread.isAlive());
}
out.println("</body>");
out.println("</html>");
}
}
在红色的代码块里，我们修改了JobExecutorServlet里获取JbpmConfiguration的方式。
再次启动工程，还是有异常发生，主要原因是JobExecutorServlet里获取了JbpmConfiguration对象后调用了startJobExecutor方法：
  public void startJobExecutor() {
    getJobExecutor().start();
  }

  public synchronized JobExecutor getJobExecutor() {
    if (jobExecutor==null) {
      try {
        jobExecutor = (JobExecutor) this.objectFactory.createObject("jbpm.job.executor");
      } catch (ClassCastException e) {
        throw new JbpmException("jbpm configuration object under key 'jbpm.job.executor' is not a "+JobExecutor.class.getName(), e);
      }
    }
    return jobExecutor;
  }
深入其代码，我们明白了它报错的原因是JobExecutor是从jbpm.cfg.xml里来的：
<bean name="jbpm.job.executor" class="org.jbpm.job.executor.JobExecutor">
    <field name="jbpmConfiguration"><ref bean="jbpmConfiguration" /></field>
    <field name="name"><string value="JbpmJobExector" /></field>
    <field name="nbrOfThreads"><int value="1" /></field>
    <field name="idleInterval"><int value="5000" /></field>
    <field name="maxIdleInterval"><int value="3600000" /></field> <!-- 1 hour -->
    <field name="historyMaxSize"><int value="20" /></field>
    <field name="maxLockTime"><int value="600000" /></field> <!-- 10 minutes -->
    <field name="lockMonitorInterval"><int value="60000" /></field> <!-- 1 minute -->
    <field name="lockBufferTime"><int value="5000" /></field> <!-- 5 seconds -->
  </bean>
我们看到里面有“<field name="jbpmConfiguration"><ref bean="jbpmConfiguration" /></field>”因为我们没有采用Hibernate.cfg.xml，所以在JobExecutor得不到jbpmConfiguration对象所致，因此我们需要在调用JobExecutor时对JobExecutor里的jbpmConfiguration进行初始化，这里我们选择对JobExecutor类进行扩展，而不是对其进行修改，扩展的代码类如下：
package org.jbpm.job.executor;

import org.jbpm.JbpmConfiguration;

public class CustomJobExecutor extends JobExecutor{
public static JbpmConfiguration jbpmConfig;
public synchronized void start() {
jbpmConfiguration = jbpmConfig;
super.start();
}
public static void setJbpmConfiguration(JbpmConfiguration config){
jbpmConfig=config;
}
}
同时对JobExecutorServlet做修改，主要目的是在该servlet进行初始化时为CustomJobExecutor类的jbpmConfig进行初始化。代码如下：

package org.jbpm.job.executor;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collection;
import java.util.Iterator;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.jbpm.JbpmConfiguration;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springmodules.workflow.jbpm31.JbpmTemplate;

public class JobExecutorServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

JbpmConfiguration jbpmConfiguration;
//修改了JobExecutorServlet里获取JbpmConfiguration的方式
public void init() throws ServletException {
JbpmTemplate jbpmTemplate = (JbpmTemplate) WebApplicationContextUtils
.getWebApplicationContext(this.getServletContext()).getBean(
"jbpmTemplate");
jbpmConfiguration = jbpmTemplate.getJbpmConfiguration();
CustomJobExecutor.setJbpmConfiguration(jbpmConfiguration);
jbpmConfiguration.startJobExecutor();
}

protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body>");
out.println("<h2>JBoss jBPM Scheduler Servlet</h2><hr />");
Collection threads = jbpmConfiguration.getJobExecutor().getThreads()
.values();
Iterator iter = threads.iterator();
while (iter.hasNext()) {
Thread thread = (Thread) iter.next();
out.println("<h4>" + thread.getName() + "</h4>");
out.println("<b>isAlive</b>:" + thread.isAlive());
}
out.println("</body>");
out.println("</html>");
}
}

再次启动工程，一切正常，没有异常发生，证明我们的修改工作达到的预期的效果。

评论

1 楼 flying_all 2009-02-24  

错了。怎么能踩呢。我在我的工程中成功了。只是我用的是struts2.在serlvet的拦截器中把JobExecutorServlet 中init的代码执行了一次。就可以用了。