org.drools.core.base.evaluators

Class StartsEvaluatorDefinition

java.lang.Object

org.drools.core.base.evaluators.StartsEvaluatorDefinition

All Implemented Interfaces:

Externalizable, Serializable, 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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	StartsEvaluatorDefinition.StartsEvaluator Implements the 'starts' evaluator itself

Nested classes/interfaces inherited from interface org.drools.core.base.evaluators.EvaluatorDefinition

EvaluatorDefinition.Target

Field Summary

Fields

Modifier and Type	Field and Description
static Operator	STARTS
static Operator	STARTS_NOT
protected static String	startsOp

Constructor Summary

Constructors

Constructor and Description
StartsEvaluatorDefinition()

Method Summary

Modifier and Type	Method and Description
Evaluator	getEvaluator(ValueType type, Operator operator) Returns the evaluator instance for the given type and the defined parameterText
Evaluator	getEvaluator(ValueType type, Operator operator, String parameterText) Returns the evaluator instance for the given type and the defined parameterText
Evaluator	getEvaluator(ValueType type, String operatorId, boolean isNegated, String parameterText) Returns the evaluator instance for the given type and the defined parameterText
Evaluator	getEvaluator(ValueType type, String operatorId, boolean isNegated, String parameterText, EvaluatorDefinition.Target left, EvaluatorDefinition.Target right) Returns the evaluator instance for the given type and the defined parameterText
String[]	getEvaluatorIds() Returns the list of identifies this evaluator implementation supports
EvaluatorDefinition.Target	getTarget() There are evaluators that operate on *fact* attributes, evaluators that operate on *fact handle* attributes, and evaluators that operate on both.
boolean	isNegatable() My apologies to English speakers if the word "negatable" does not exist. :) This method returns true if this evaluator supports negation.
void	readExternal(ObjectInput in)
boolean	supportsType(ValueType type) Returns true in case this evaluator supports operations over values of that specific type.
void	writeExternal(ObjectOutput out)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

startsOp

protected static final String startsOp

See Also:

Constant Field Values

STARTS

public static Operator STARTS

STARTS_NOT

public static Operator STARTS_NOT

Constructor Detail

StartsEvaluatorDefinition

public StartsEvaluatorDefinition()

Method Detail

readExternal

public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException

Specified by:

readExternal in interface Externalizable

Throws:

IOException

ClassNotFoundException

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Specified by:

writeExternal in interface Externalizable

Throws:

IOException

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

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

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

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

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.

getEvaluatorIds

public String[] getEvaluatorIds()

Description copied from interface: EvaluatorDefinition

Returns the list of identifies this evaluator implementation supports

Returns:

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" (!?)

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.

Returns:

true if this evaluator operates on fact handle attributes and false if it operates on fact attributes

supportsType

public boolean supportsType(ValueType type)

Description copied from interface: EvaluatorDefinition

Returns true in case this evaluator supports operations over values of that specific type.

Returns: