Trigger Execution Conditions

A trigger is registered with an execution condition and a command or server code to execute when the execution condition is met. You can use the following three conditions:

  • One-Time Schedule
  • Recurring Schedule
  • State Condition

One-Time Schedule

This condition will fire the trigger just once at the designated time.

Use the ScheduleOncePredicate class to use a one-time schedule.

Specify the time to execute the trigger with the constructor of the SchgeduleOncePredicate. Specify the time in UNIX time in milliseconds (UTC).

Recurring Schedule

This condition will fire the trigger on the scheduled interval.

Use the SchedulePredicate class to use a recurring schedule.

Specify the time to execute the trigger with the constructor of the SchedulePredicate in the cron expression.

State Condition

This condition will fire the trigger based on the latest field values of the thing state. The trigger condition is composed of two parts. The first part is the comparison condition that defines how to make the comparison with the state, and the second part is the execution condition that defines how to associate the comparison condition and the actual trigger execution.

Use the StatePredicate class to use the state condition.

The state condition is defined by the following two conditions.

Comparison Condition

You will specify how to make the comparison with the latest state's fields using the subclasses of the Clause class. Please also check the class diagram.

You will use the following methods in the Clause subclass to define the condition.

Method Comparison to be defined
Equals constructor True if the field value is equal to the specified value.
NotEquals constructor True if the field value is not equal to the specified value. You will first create an Equals object and then pass it to NotEquals as an argument.
Range constructor True if the field value is in between the specified values. You can also specify if you want to treat the upper and lower values inclusively or exclusively.
Range.greaterThan method True if the field value is greater than the specified value.
Range.greaterThanEquals method True if the field value is greater than or equal to the specified value.
Range.lessThan method True if the field value is less than the specified value.
Range.lessThanEquals method True if the field value is less than or equal to the specified value.
And constructor Concatenate multiple conditions with AND. True if all the specified Clauses are true.
Or constructor Concatenate multiple conditions with OR. True if at least one of the specified Clauses is true.

Use the combination of the above methods to create a Clause instance that defines your comparison condition.

Execution Condition

You can specify how to associate the comparison condition and the actual trigger execution. The following three conditions are available:

Value Association to be made
TriggersWhen.CONDITION_TRUE Execute the trigger if the comparison condition is true.
TriggersWhen.CONDITION_FALSE_TO_TRUE Execute the trigger if the comparison condition was false and becomes true.
TriggersWhen.CONDITION_CHANGED Execute the trigger if the comparison condition changes.

If you want to set the association like "when the comparison condition is false" and "when the condition was true and becomes false", please consider reverting the comparison conditions. You can also use Equals(clause, false).

When using CONDITION_TRUE, be aware that the command/server code could be executed every time the state is updated. If you set a condition "the room temperature is above 30 degrees" with CONDITION_TRUE, for example, the associated command/server code will be executed every time the thing state is updated as long as the room temperature is over 30 degrees.

If you register multiple triggers with the same condition, all of them will execute the designated command/server code when the specified condition is met. Please avoid registering duplicate triggers by checking a list of triggers.