Java Trigger tutorial with examples
Triggers allow application developers to plug in rules for when and how often a task should run. The trigger can be as simple as a single, absolute date-time or can include Java™ EE business calendar logic. A Trigger implementation is created by the application developer (or may be supplied to the application externally) and is registered with a task when it is submitted to a ManagedScheduledExecutorService using any of the schedule methods. Each method will run with unspecified context. The methods can be made contextual through creating contextual proxy objects using ContextService.
Each Trigger instance will be invoked within the same process in which it was registered.
/** * A trigger that only returns a single date. */ public class SingleDateTrigger implements Trigger < private Date fireTime; public TriggerSingleDate(Date newDate) < fireTime = newDate; >public Date getNextRunTime( LastExecution lastExecutionInfo, Date taskScheduledTime) < if(taskScheduledTime.after(fireTime)) < return null; >return fireTime; > public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) < return scheduledRunTime.after(fireTime); >> /** * A fixed-rate trigger that will skip any runs if * the latencyAllowance threshold is exceeded (the task * ran too late). */ public class TriggerFixedRateLatencySensitive implements Trigger < private Date startTime; private long delta; private long latencyAllowance; public TriggerFixedRateLatencySensitive(Date startTime, long delta, long latencyAllowance) < this.startTime = startTime; this.delta = delta; this.latencyAllowance = latencyAllowance; >public Date getNextRunTime(LastExecution lastExecutionInfo, Date taskScheduledTime) < if(lastExecutionInfo==null) < return startTime; >return new Date(lastExecutionInfo.getScheduledStart().getTime() + delta); > public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) < return System.currentTimeMillis() - scheduledRunTime.getTime() >latencyAllowance; > >
Example
The following code shows how to use Trigger from javax.enterprise.concurrent.
import javax.enterprise.concurrent.LastExecution; import javax.enterprise.concurrent.Trigger; import java.util.Date; public class MyTrigger implements Trigger private final Date firetime; public MyTrigger(Date firetime) < this.firetime = firetime; >// w w w . d e m o 2 s . co m @Override public Date getNextRunTime(LastExecution le, Date taskScheduledTime) < if (firetime.before(taskScheduledTime)) < return null; > return firetime; > @Override public boolean skipRun(LastExecution le, Date scheduledRunTime) < return firetime.before(scheduledRunTime); > >
import java.util.Calendar; import java.util.Date; import javax.enterprise.concurrent.LastExecution; import javax.enterprise.concurrent.Trigger; /**/* ww w. d e mo 2 s . c o m */ * * @author Juneau */ public class TestTrigger implements Trigger Date initialDate; public TestTrigger(Date initial) < this.initialDate = initial; > @Override public Date getNextRunTime(LastExecution lastExecutionInfo, Date taskScheduledTime) < // implementation return null; > @Override public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) < // test implementation return false; > >
/*/* ww w . d e m o 2 s . c o m */ * To change this template, choose Tools | Templates * and open the template in the editor. */ import java.util.Date; import javax.enterprise.concurrent.LastExecution; import javax.enterprise.concurrent.Trigger; /** * * @author cmp */ public class TriggerFixedRateLatencySensitive implements Trigger private Date startTime; private long delta; private long latencyAllowance; public TriggerFixedRateLatencySensitive(Date startTime, long delta, long latencyAllowance) < this.startTime = startTime; this.delta = delta; this.latencyAllowance = latencyAllowance; > @Override public Date getNextRunTime(LastExecution lastExecutionInfo, Date taskScheduledTime) < if (lastExecutionInfo == null) < return startTime; > return new Date(lastExecutionInfo.getScheduledStart().getTime() + delta); > @Override public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) < return System.currentTimeMillis() - scheduledRunTime.getTime() > latencyAllowance; > >
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Trigger class in java
Triggers allow application developers to plug in rules for when and how often a task should run. The trigger can be as simple as a single, absolute date-time or can include Java™ EE business calendar logic. A Trigger implementation is created by the application developer (or may be supplied to the application externally) and is registered with a task when it is submitted to a ManagedScheduledExecutorService using any of the schedule methods. Each method will run with unspecified context. The methods can be made contextual through creating contextual proxy objects using ContextService . Each Trigger instance will be invoked within the same process in which it was registered. Example:
/** * A trigger that only returns a single date. */ public class SingleDateTrigger implements Trigger < private Date fireTime; public TriggerSingleDate(Date newDate) < fireTime = newDate; >public Date getNextRunTime( LastExecution lastExecutionInfo, Date taskScheduledTime) < if(taskScheduledTime.after(fireTime)) < return null; >return fireTime; > public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) < return scheduledRunTime.after(fireTime); >> /** * A fixed-rate trigger that will skip any runs if * the latencyAllowance threshold is exceeded (the task * ran too late). */ public class TriggerFixedRateLatencySensitive implements Trigger < private Date startTime; private long delta; private long latencyAllowance; public TriggerFixedRateLatencySensitive(Date startTime, long delta, long latencyAllowance) < this.startTime = startTime; this.delta = delta; this.latencyAllowance = latencyAllowance; >public Date getNextRunTime(LastExecution lastExecutionInfo, Date taskScheduledTime) < if(lastExecutionInfo==null) < return startTime; >return new Date(lastExecutionInfo.getScheduledStart().getTime() + delta); > public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) < return System.currentTimeMillis() - scheduledRunTime.getTime() >latencyAllowance; > >
Method Summary
Method Detail
getNextRunTime
Date getNextRunTime(LastExecution lastExecutionInfo, Date taskScheduledTime)
skipRun
boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime)
Return true if this run instance should be skipped. This is useful if the task shouldn’t run because it is late or if the task is paused or suspended. Once this task is skipped, the state of it’s Future’s result will throw a SkippedException . Unchecked exceptions will be wrapped in a SkippedException .
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