cascading.operation.expression

Class ExpressionFilter

java.lang.Object

cascading.operation.BaseOperation<ScriptOperation.Context>

cascading.operation.expression.ScriptOperation

cascading.operation.expression.ExpressionOperation

cascading.operation.expression.ExpressionFilter

All Implemented Interfaces:

cascading.flow.planner.DeclaresResults, cascading.operation.Filter<ScriptOperation.Context>, cascading.operation.Operation<ScriptOperation.Context>, cascading.util.Traceable, java.io.Serializable

public class ExpressionFilter
extends ExpressionOperation
implements cascading.operation.Filter<ScriptOperation.Context>

Class ExpressionFilter dynamically resolves a given expression using argument Tuple values. Any Tuple that returns true for the given expression will be removed from the stream. This Filter is based on the Janino compiler.

Specifically this filter uses the ExpressionEvaluator, thus the syntax from that class is inherited here.

An expression may use field names directly as parameters in the expression, or field positions with the syntax "$n", where n is an integer.

Given an argument tuple with the fields "a" and "b", the following expression returns true:
a + b == $0 + $1

Further, the types of the tuple elements will be coerced into the given parameterTypes. Regardless of the actual tuple element values, they will be converted to the types expected by the expression.

Field names used in the expression should be valid Java variable names; for example, '+' or '-' are not allowed. Also the use of a field name that begins with an upper-case character is likely to fail and should be avoided.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class cascading.operation.expression.ScriptOperation

ScriptOperation.Context, ScriptOperation.Evaluator

Field Summary

Fields inherited from class cascading.operation.expression.ScriptOperation

block, parameterNames, parameterTypes, returnType

Fields inherited from class cascading.operation.BaseOperation

fieldDeclaration, numArgs, trace

Fields inherited from interface cascading.operation.Operation

ANY

Constructor Summary

Constructors

Constructor and Description
ExpressionFilter(java.lang.String expression) Constructor ExpressionFilter creates a new ExpressionFilter instance.
ExpressionFilter(java.lang.String expression, java.lang.Class parameterType) Constructor ExpressionFilter creates a new ExpressionFilter instance.
ExpressionFilter(java.lang.String expression, java.lang.String[] parameterNames, java.lang.Class[] parameterTypes) Constructor ExpressionFilter creates a new ExpressionFilter instance.

Method Summary

Modifier and Type	Method and Description
boolean	isRemove(cascading.flow.FlowProcess flowProcess, cascading.operation.FilterCall<ScriptOperation.Context> filterCall)

Methods inherited from class cascading.operation.expression.ExpressionOperation

getEvaluator, getExpression, guessParameterNames

Methods inherited from class cascading.operation.expression.ScriptOperation

equals, evaluate, getBlock, getExtendedClass, getParameterNames, getParameterTypes, getReturnType, hashCode, prepare

Methods inherited from class cascading.operation.BaseOperation

cleanup, flush, getFieldDeclaration, getNumArgs, getTrace, isSafe, printOperationInternal, toString, toStringInternal

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface cascading.operation.Operation

cleanup, flush, getFieldDeclaration, getNumArgs, isSafe, prepare

Constructor Detail

ExpressionFilter

@ConstructorProperties(value="expression")
public ExpressionFilter(java.lang.String expression)

Constructor ExpressionFilter creates a new ExpressionFilter instance.

This constructor, when used with incoming arguments that have type information, the argument field names can be used directly in the the expression, for example a + b . The type of a and b will be inherited from the incoming argument fields.

Or, if the incoming argument selector is Fields.NONE, an expression using only static method calls or constants can be used, for example Math.random() < SomeClass.someValue() .

Parameters:

expression - of type String

ExpressionFilter

@ConstructorProperties(value={"expression","parameterType"})
public ExpressionFilter(java.lang.String expression,
                                                                                     java.lang.Class parameterType)

Constructor ExpressionFilter creates a new ExpressionFilter instance.

Parameters:

expression - of type String

parameterType - of type Class

ExpressionFilter

@ConstructorProperties(value={"expression","parameterNames","parameterTypes"})
public ExpressionFilter(java.lang.String expression,
                                                                                                       java.lang.String[] parameterNames,
                                                                                                       java.lang.Class[] parameterTypes)

Constructor ExpressionFilter creates a new ExpressionFilter instance.

Parameters:

expression - of type String

parameterNames - of type String[]

parameterTypes - of type Class[]

Method Detail

isRemove

public boolean isRemove(cascading.flow.FlowProcess flowProcess,
                        cascading.operation.FilterCall<ScriptOperation.Context> filterCall)

Specified by:

isRemove in interface cascading.operation.Filter<ScriptOperation.Context>