SchedulerThread


1   package org.jbpm.scheduler.impl;
2   
3   import java.util.ArrayList  ;
4   import java.util.Date  ;
5   import java.util.Iterator  ;
6   import java.util.List  ;
7   
8   import org.apache.commons.logging.Log;
9   import org.apache.commons.logging.LogFactory;
10  import org.jbpm.calendar.BusinessCalendar;
11  import org.jbpm.calendar.Duration;
12  import org.jbpm.db.JbpmSession;
13  import org.jbpm.db.JbpmSessionFactory;
14  import org.jbpm.db.SchedulerSession;
15  import org.jbpm.scheduler.exe.Timer;
16  
17  public class SchedulerThread extends Thread   {
18    
19    static JbpmSessionFactory jbpmSessionFactory = JbpmSessionFactory.getInstance();
20    static BusinessCalendar businessCalendar = new BusinessCalendar();
21    
22    List   listeners = new ArrayList  ();
23    boolean keepRunning = true;
24    long interval = 5000;
25    
26    public SchedulerThread() {
27      super("jbpm scheduler");
28    }
29  
30    public void run() {
31      while (keepRunning) {
32        long millisToWait = interval;
33        try {
34          millisToWait = executeTimers();
35  
36          // calculate the milliseconds to wait...
37          if (millisToWait < 0) {
38            millisToWait = interval;
39          }
40          millisToWait = Math.min(millisToWait, interval);
41  
42        } catch (RuntimeException   e) {
43          log.info("runtime exception while executing timers", e);
44        } finally {
45          try {
46            Thread.sleep(millisToWait);
47          } catch (InterruptedException   e) {
48            log.info("waiting for timers got interuppted");
49          }
50        }
51      }
52      log.info("ending scheduler thread");
53    }
54    
55    /**
56     * executes due timers and calculates the time before the next timer is due.
57     * @return the number of milliseconds till the next job is due or -1 if no timer is 
58     * schedulerd in the future.
59     */
60    public long executeTimers() {
61      long millisTillNextTimerIsDue = -1;
62      boolean isDueDateInPast = true;
63      
64      JbpmSession jbpmSession = jbpmSessionFactory.openJbpmSessionAndBeginTransaction();
65      try {
66        SchedulerSession schedulerSession = new SchedulerSession(jbpmSession);
67        
68        log.debug("checking for timers");
69        Iterator   iter = schedulerSession.findTimersByDueDate();
70        while( (iter.hasNext())
71               && (isDueDateInPast)
72             ) {
73          Timer timer = (Timer) iter.next();
74          log.debug("found timer "+timer);
75          
76          // if this timer is due
77          if (timer.isDue()) {
78            log.debug("executing timer '"+timer+"'");
79              
80            // execute
81            timer.execute();
82              
83            // notify the listeners (e.g. the scheduler servlet)
84            notifyListeners(timer);
85              
86            // if there was an exception, just save the timer
87            if (timer.getException()!=null) {
88              schedulerSession.saveTimer(timer);
89              
90            // if repeat is specified
91            } else if (timer.getRepeat()!=null) {
92              // update timer by adding the repeat duration
93              Date   dueDate = timer.getDueDate();
94              
95              // suppose that it took the timer runner thread a 
96              // very long time to execute the timers.
97              // then the repeat action dueDate could already have passed.
98              while (dueDate.getTime()<=System.currentTimeMillis()) {
99                dueDate = businessCalendar
100                     .add(dueDate, 
101                       new Duration(timer.getRepeat()));
102             }
103             timer.setDueDate( dueDate );
104             // save the updated timer in the database
105             log.debug("saving updated timer for repetition '"+timer+"' in '"+(dueDate.getTime()-System.currentTimeMillis())+"' millis");
106             schedulerSession.saveTimer(timer);
107             
108           } else {
109             // delete this timer
110             log.debug("deleting timer '"+timer+"'");
111             schedulerSession.deleteTimer(timer);
112           }
113 
114         } else { // this is the first timer that is not yet due
115           isDueDateInPast = false;
116           millisTillNextTimerIsDue = timer.getDueDate().getTime() - System.currentTimeMillis();
117         }
118       }
119       
120     } finally {
121       jbpmSession.commitTransactionAndClose();
122     }
123     
124     return millisTillNextTimerIsDue;
125   }
126 
127   // listeners ////////////////////////////////////////////////////////////////
128 
129   public void addListener(SchedulerListener listener) {
130     if (listeners==null) listeners = new ArrayList  ();
131     listeners.add(listener);
132   }
133 
134   public void removeListener(SchedulerListener listener) {
135     listeners.remove(listener);
136     if (listeners.isEmpty()) {
137       listeners = null;
138     }
139   }
140 
141   private void notifyListeners(Timer timer) {
142     if (listeners!=null) {
143       Date   now = new Date  ();
144       Iterator   iter = new ArrayList  (listeners).iterator();
145       while (iter.hasNext()) {
146         SchedulerListener timerRunnerListener = (SchedulerListener) iter.next();
147         timerRunnerListener.timerExecuted(now, timer);
148       }
149     }
150   }
151 
152   public void setInterval(long interval) {
153     this.interval = interval;
154   }
155   
156   private static final Log log = LogFactory.getLog(SchedulerThread.class);
157 }
158
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