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@jteso
Created February 1, 2012 23:17
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A trigger for periodic task execution with the added capability to modify runtime the period between polls.
package directlabs.integration;
import java.util.Date;
import java.util.concurrent.TimeUnit;
import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.TriggerContext;
import org.springframework.util.Assert;
/**
* A trigger for periodic task execution with the added capability to modify runtime the period between
* polls. A desired behavior when you are trying to throttle inbound messages via polling rate.
*
* @author jtedilla
* @see org.springframework.scheduling.support.PeriodicTrigger
*/
public class DynamicTrigger implements Trigger{
private long period;
private final TimeUnit timeUnit;
private volatile long initialDelay = 0;
private volatile boolean fixedRate = false;
/**
* Create a trigger with the given period in milliseconds.
*/
public DynamicTrigger(long period) {
this(period, null);
}
/**
* Create a trigger with the given period and time unit. The time unit will
* apply not only to the period but also to any 'initialDelay' value, if
* configured on this Trigger later via {@link #setInitialDelay(long)}.
*/
public DynamicTrigger(long period, TimeUnit timeUnit) {
Assert.isTrue(period >= 0, "period must not be negative");
this.timeUnit = (timeUnit != null) ? timeUnit : TimeUnit.MILLISECONDS;
this.period = this.timeUnit.toMillis(period);
}
/**
* Specify a new period. Very useful when you try to throttle inbound messages by
* modifying the polling rate.
*/
public void setPeriod(long newPeriod){
this.period = newPeriod;
}
/**
* Specify the delay for the initial execution. It will be evaluated in
* terms of this trigger's {@link TimeUnit}. If no time unit was explicitly
* provided upon instantiation, the default is milliseconds.
*/
public void setInitialDelay(long initialDelay) {
this.initialDelay = this.timeUnit.toMillis(initialDelay);
}
/**
* Specify whether the periodic interval should be measured between the
* scheduled start times rather than between actual completion times.
* The latter, "fixed delay" behavior, is the default.
*/
public void setFixedRate(boolean fixedRate) {
this.fixedRate = fixedRate;
}
/**
* Returns the time after which a task should run again.
*/
public Date nextExecutionTime(TriggerContext triggerContext) {
if (triggerContext.lastScheduledExecutionTime() == null) {
return new Date(System.currentTimeMillis() + this.initialDelay);
}
else if (this.fixedRate) {
return new Date(triggerContext.lastScheduledExecutionTime().getTime() + this.period);
}
return new Date(triggerContext.lastCompletionTime().getTime() + this.period);
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + (fixedRate ? 1231 : 1237);
result = prime * result + (int) (initialDelay ^ (initialDelay >>> 32));
result = prime * result + (int) (period ^ (period >>> 32));
result = prime * result
+ ((timeUnit == null) ? 0 : timeUnit.hashCode());
return result;
}
}
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