org.springframework.scheduling.support

## Class PeriodicTrigger

- java.lang.Object
- - org.springframework.scheduling.support.PeriodicTrigger

All Implemented Interfaces:
  Trigger

    public class PeriodicTrigger
    extends Object
    implements Trigger

A trigger for periodic task execution. The period may be applied as either fixed-rate or fixed-delay, and an initial delay value may also be configured. The default initial delay is 0, and the default behavior is fixed-delay (i.e. the interval between successive executions is measured from each <emphasis>completion</emphasis> time). To measure the interval between the scheduled <emphasis>start</emphasis> time of each execution instead, set the 'fixedRate' property to `true`.

Note that the TaskScheduler interface already defines methods for scheduling tasks at fixed-rate or with fixed-delay. Both also support an optional value for the initial delay. Those methods should be used directly whenever possible. The value of this Trigger implementation is that it can be used within components that rely on the Trigger abstraction. For example, it may be convenient to allow periodic triggers, cron-based triggers, and even custom Trigger implementations to be used interchangeably.

Since:
  3.0
Author:
  Mark Fisher

### Constructor Summary

Constructors
Constructor and Description
`PeriodicTrigger(long period)` Create a trigger with the given period in milliseconds.
`PeriodicTrigger(long period, TimeUnit timeUnit)` Create a trigger with the given period and time unit.

### Method Summary

Methods
`boolean` `equals(Object obj)`
`int` `hashCode()`
`Date` `nextExecutionTime(TriggerContext triggerContext)` Returns the time after which a task should run again.
`void` `setFixedRate(boolean fixedRate)` Specify whether the periodic interval should be measured between the scheduled start times rather than between actual completion times.
`void` `setInitialDelay(long initialDelay)` Specify the delay for the initial execution.

### Methods inherited from class java.lang.Object

`clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

### Constructor Detail

#### PeriodicTrigger

    public PeriodicTrigger(long period)

Create a trigger with the given period in milliseconds.

#### PeriodicTrigger

    public PeriodicTrigger(long period,
                   TimeUnit timeUnit)

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 `setInitialDelay(long)`.

### Method Detail

#### setInitialDelay

    public void setInitialDelay(long initialDelay)

Specify the delay for the initial execution. It will be evaluated in terms of this trigger's `TimeUnit`. If no time unit was explicitly provided upon instantiation, the default is milliseconds.

#### setFixedRate

    public void setFixedRate(boolean fixedRate)

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.

#### nextExecutionTime

    public Date nextExecutionTime(TriggerContext triggerContext)

Returns the time after which a task should run again.

Specified by:
  `nextExecutionTime` in interface `Trigger`
Parameters:
  `triggerContext` - context object encapsulating last execution times and last completion time
Returns:
  the next execution time as defined by the trigger, or `null` if the trigger won't fire anymore

#### equals

    public boolean equals(Object obj)

Overrides:
  `equals` in class `Object`

#### hashCode

    public int hashCode()

Overrides:
  `hashCode` in class `Object`