Package org.drools.core.base.evaluators

Class StartsEvaluatorDefinition

  • All Implemented Interfaces:
    Externalizable, Serializable, EvaluatorDefinition, org.kie.api.runtime.rule.EvaluatorDefinition
    public class StartsEvaluatorDefinition
extends Object
implements EvaluatorDefinition

    The implementation of the starts evaluator definition.

    The starts evaluator correlates two events and matches when the current event's end timestamp happens before the correlated event's end timestamp, but both start timestamps occur at the same time.

    Lets look at an example:

    $eventA : EventA( this starts $eventB )

    The previous pattern will match if and only if the $eventA finishes before $eventB finishes and starts at the same time $eventB starts. In other words:

     
 $eventA.startTimestamp == $eventB.startTimestamp &&
 $eventA.endTimestamp < $eventB.endTimestamp

    The starts evaluator accepts one optional parameter. If it is defined, it determines the maximum distance between the start timestamp of both events in order for the operator to match. Example:

    $eventA : EventA( this starts[ 5s ] $eventB )
    Will match if and only if: 
     
 abs( $eventA.startTimestamp - $eventB.startTimestamp ) <= 5s &&
 $eventA.endTimestamp < $eventB.endTimestamp

    NOTE: it makes no sense to use a negative interval value for the parameter and the engine will raise an exception if that happens.

    See Also:
    Serialized Form

    • Constructor Detail

      • StartsEvaluatorDefinition

        public StartsEvaluatorDefinition()

    • Method Detail

      • getEvaluator

        public Evaluator getEvaluator​(ValueType type,
                              Operator operator)
        Description copied from interface: EvaluatorDefinition
        Returns the evaluator instance for the given type and the defined parameterText
        Specified by:
        getEvaluator in interface EvaluatorDefinition
        Parameters:
        type - the type of the attributes this evaluator will operate on. This is important because the evaluator may do optimisations and type coercion based on the types it is evaluating. It is also possible that this evaluator does not support a given type.
        operator - the operator implemented by the evaluator
        Returns:
        an Evaluator instance capable of evaluating expressions between values of the given type, or null in case the type is not supported.

      • getEvaluator

        public Evaluator getEvaluator​(ValueType type,
                              Operator operator,
                              String parameterText)
        Description copied from interface: EvaluatorDefinition
        Returns the evaluator instance for the given type and the defined parameterText
        Specified by:
        getEvaluator in interface EvaluatorDefinition
        Parameters:
        type - the type of the attributes this evaluator will operate on. This is important because the evaluator may do optimisations and type coercion based on the types it is evaluating. It is also possible that this evaluator does not support a given type.
        operator - the operator implemented by the evaluator
        parameterText - some evaluators support parameters and these parameters are defined as a String that is parsed by the evaluator itself.
        Returns:
        an Evaluator instance capable of evaluating expressions between values of the given type, or null in case the type is not supported.

      • getEvaluator

        public Evaluator getEvaluator​(ValueType type,
                              String operatorId,
                              boolean isNegated,
                              String parameterText)
        Description copied from interface: EvaluatorDefinition
        Returns the evaluator instance for the given type and the defined parameterText
        Specified by:
        getEvaluator in interface EvaluatorDefinition
        Parameters:
        type - the type of the attributes this evaluator will operate on. This is important because the evaluator may do optimisations and type coercion based on the types it is evaluating. It is also possible that this evaluator does not support a given type.
        operatorId - the string identifier of the evaluator
        isNegated - true if the evaluator instance to be returned is the negated version of the evaluator.
        parameterText - some evaluators support parameters and these parameters are defined as a String that is parsed by the evaluator itself.
        Returns:
        an Evaluator instance capable of evaluating expressions between values of the given type, or null in case the type is not supported.

      • getEvaluator

        public Evaluator getEvaluator​(ValueType type,
                              String operatorId,
                              boolean isNegated,
                              String parameterText,
                              EvaluatorDefinition.Target left,
                              EvaluatorDefinition.Target right)
        Description copied from interface: EvaluatorDefinition
        Returns the evaluator instance for the given type and the defined parameterText
        Specified by:
        getEvaluator in interface EvaluatorDefinition
        Parameters:
        type - the type of the attributes this evaluator will operate on. This is important because the evaluator may do optimisations and type coercion based on the types it is evaluating. It is also possible that this evaluator does not support a given type.
        operatorId - the string identifier of the evaluator
        isNegated - true if the evaluator instance to be returned is the negated version of the evaluator.
        parameterText - some evaluators support parameters and these parameters are defined as a String that is parsed by the evaluator itself.
        left - the target of the evaluator on the Left side, i.e., on Rete terms, the previous binding or the actual value on the right side of the operator.
        right - the target of the evaluator on the Right side, i.e., on Rete terms, the current pattern field.
        Returns:
        an Evaluator instance capable of evaluating expressions between values of the given type, or null in case the type is not supported.

      • isNegatable

        public boolean isNegatable()
        Description copied from interface: EvaluatorDefinition
        My apologies to English speakers if the word "negatable" does not exist. :) This method returns true if this evaluator supports negation. Example: the "matches" operator supports "not matches" and so is "negatable" (!?)
        Specified by:
        isNegatable in interface EvaluatorDefinition
        Returns:

      • getTarget

        public EvaluatorDefinition.Target getTarget()
        Description copied from interface: EvaluatorDefinition
        There are evaluators that operate on *fact* attributes, evaluators that operate on *fact handle* attributes, and evaluators that operate on both. This method returns the target of the current evaluator.
        Specified by:
        getTarget in interface EvaluatorDefinition
        Returns:
        true if this evaluator operates on fact handle attributes and false if it operates on fact attributes