com.espertech.esper.epl.expression.core
Class ExprConstantNodeImpl

java.lang.Object
  com.espertech.esper.epl.expression.core.ExprNodeBase
      com.espertech.esper.epl.expression.core.ExprConstantNodeImpl

All Implemented Interfaces:

ExprConstantNode, ExprEvaluator, ExprNode, ExprValidator, MetaDefItem, java.io.Serializable

public class ExprConstantNodeImpl
extends ExprNodeBase
implements ExprConstantNode, ExprEvaluator

Represents a constant in an expressiun tree.

See Also:

Serialized Form

Constructor Summary

ExprConstantNodeImpl(java.lang.Class clazz)
Ctor - for use when the constant should return a given type and the actual value is always null.

ExprConstantNodeImpl(java.lang.Object value)
Ctor.

ExprConstantNodeImpl(java.lang.Object value, java.lang.Class valueType)
Ctor.

Method Summary

boolean	equalsNode(ExprNode node) Return true if a expression node semantically equals the current node, or false if not.
java.lang.Object	evaluate(EventBean[] eventsPerStream, boolean isNewData, ExprEvaluatorContext exprEvaluatorContext) Evaluate event tuple and return result.
java.lang.Class	getConstantType()
java.lang.Object	getConstantValue(ExprEvaluatorContext context) Returns the constant's value.
ExprEvaluator	getExprEvaluator()
ExprPrecedenceEnum	getPrecedence() Returns precedence.
java.lang.Class	getType() Returns the type that the node's evaluate method returns an instance of.
boolean	isConstantResult() Returns true if the expression node's evaluation value doesn't depend on any events data, as must be determined at validation time, which is bottom-up and therefore reliably allows each node to determine constant value.
boolean	isConstantValue()
void	setValue(java.lang.Object value) Sets the value of the constant.
void	toPrecedenceFreeEPL(java.io.StringWriter writer)
ExprNode	validate(ExprValidationContext validationContext)

Methods inherited from class com.espertech.esper.epl.expression.core.ExprNodeBase

accept, accept, acceptChildnodes, addChildNode, addChildNodes, addChildNodeToFront, getChildNodes, replaceUnlistedChildNode, setChildNode, setChildNodes, toEPL

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.espertech.esper.epl.expression.core.ExprNode

accept, accept, acceptChildnodes, addChildNode, addChildNodes, getChildNodes, replaceUnlistedChildNode, setChildNode, setChildNodes, toEPL

Constructor Detail

ExprConstantNodeImpl

public ExprConstantNodeImpl(java.lang.Object value)

Ctor.

Parameters:

value - is the constant's value.

ExprConstantNodeImpl

public ExprConstantNodeImpl(java.lang.Object value,
                            java.lang.Class valueType)

Ctor.

Parameters:

value - is the constant's value.

valueType - is the constant's value type.

ExprConstantNodeImpl

public ExprConstantNodeImpl(java.lang.Class clazz)

Ctor - for use when the constant should return a given type and the actual value is always null.

Parameters:

clazz - the type of the constant null.

Method Detail

isConstantValue

public boolean isConstantValue()

Specified by:

isConstantValue in interface ExprConstantNode

validate

public ExprNode validate(ExprValidationContext validationContext)
                  throws ExprValidationException

Specified by:

validate in interface ExprValidator

Throws:

ExprValidationException

isConstantResult

public boolean isConstantResult()

Description copied from interface: ExprNode

Returns true if the expression node's evaluation value doesn't depend on any events data, as must be determined at validation time, which is bottom-up and therefore reliably allows each node to determine constant value.

Specified by:

isConstantResult in interface ExprNode

Returns:

true for constant evaluation value, false for non-constant evaluation value

getConstantValue

public java.lang.Object getConstantValue(ExprEvaluatorContext context)

Returns the constant's value.

Specified by:

getConstantValue in interface ExprConstantNode

Returns:

value of constant

setValue

public void setValue(java.lang.Object value)

Sets the value of the constant.

Parameters:

value - to set

getConstantType

public java.lang.Class getConstantType()

Specified by:

getConstantType in interface ExprConstantNode

getType

public java.lang.Class getType()

Description copied from interface: ExprEvaluator

Returns the type that the node's evaluate method returns an instance of.

Specified by:

getType in interface ExprEvaluator

Returns:

type returned when evaluated

evaluate

public java.lang.Object evaluate(EventBean[] eventsPerStream,
                                 boolean isNewData,
                                 ExprEvaluatorContext exprEvaluatorContext)

Description copied from interface: ExprEvaluator

Evaluate event tuple and return result.

Specified by:

evaluate in interface ExprEvaluator

Parameters:

eventsPerStream - - event tuple

isNewData - - indicates whether we are dealing with new data (istream) or old data (rstream)

exprEvaluatorContext - context for expression evaluation

Returns:

evaluation result, a boolean value for OR/AND-type evalution nodes.

getExprEvaluator

public ExprEvaluator getExprEvaluator()

Specified by:

getExprEvaluator in interface ExprNode

toPrecedenceFreeEPL

public void toPrecedenceFreeEPL(java.io.StringWriter writer)

Specified by:

toPrecedenceFreeEPL in class ExprNodeBase

getPrecedence

public ExprPrecedenceEnum getPrecedence()

Description copied from interface: ExprNode

Returns precedence.

Specified by:

getPrecedence in interface ExprNode

Returns:

precedence

equalsNode

public boolean equalsNode(ExprNode node)

Description copied from interface: ExprNode

Return true if a expression node semantically equals the current node, or false if not.

Concrete implementations should compare the type and any additional information that impact the evaluation of a node.

Specified by:

equalsNode in interface ExprNode

Parameters:

node - to compare to

Returns:

true if semantically equal, or false if not equals