cascading.operation.expression
Class ScriptTupleFunction

java.lang.Object
  cascading.operation.BaseOperation<ScriptOperation.Context>
      cascading.operation.expression.ScriptOperation
          cascading.operation.expression.ScriptTupleFunction

All Implemented Interfaces:

cascading.flow.planner.DeclaresResults, Function<ScriptOperation.Context>, Operation<ScriptOperation.Context>, cascading.util.Traceable, Serializable

public class ScriptTupleFunction
extends ScriptOperation
implements Function<ScriptOperation.Context>

Class ScriptTupleFunction dynamically resolves a given expression using argument Tuple values. This Function is based on the Janino compiler.

This class is different from ScriptFunction in that it requires a new Tuple instance to be returned by the script. ScriptFunction allows only a single value to be returned, which is passed into a result Tuple instance internally.

Specifically this function uses the ScriptEvaluator, thus the syntax from that class is inherited here.

A script 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 script returns true:
boolean result = (a + b == $0 + $1);
return cascading.tuple.Tuples.tuple( boolean );

Unlike an "expression" used by ExpressionFunction, a "script" requires each line to end in an semi-colon (@{code ;}) and the final line to be a return statement that returns a new Tuple instance.

Since Janino does not support "varargs", see the Tuples class for helper methods.

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 script if possible.

See Also:

Serialized Form

Nested Class Summary

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

ScriptOperation.Context

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

ScriptTupleFunction(Fields fieldDeclaration, String script)
Constructor ScriptFunction creates a new ScriptFunction instance.

ScriptTupleFunction(Fields fieldDeclaration, String script, Class[] expectedTypes)
Constructor ScriptFunction creates a new ScriptFunction instance.

ScriptTupleFunction(Fields fieldDeclaration, String script, String[] parameterNames, Class[] parameterTypes)
Constructor ScriptFunction creates a new ScriptFunction instance.

Method Summary

String	getScript()
void	operate(FlowProcess flowProcess, FunctionCall<ScriptOperation.Context> functionCall) Method operate provides the implementation of this Function.

Methods inherited from class cascading.operation.expression.ScriptOperation

equals, evaluate, getBlock, getEvaluator, getParameterNames, getParameterTypes, getReturnType, guessParameterNames, 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

ScriptTupleFunction

@ConstructorProperties(value={"fieldDeclaration","script"})
public ScriptTupleFunction(Fields fieldDeclaration,
                                                      String script)

Constructor ScriptFunction creates a new ScriptFunction instance.

This constructor will use the runtime OperationCall.getArgumentFields() to source the parameterNames and parameterTypes required by the other constructors.

The returnType will be retrieved from the given fieldDeclaration.getTypeClass(0).

Parameters:

fieldDeclaration - of type Fields

script - of type String

ScriptTupleFunction

@ConstructorProperties(value={"fieldDeclaration","script","expectedTypes"})
public ScriptTupleFunction(Fields fieldDeclaration,
                                                      String script,
                                                      Class[] expectedTypes)

Constructor ScriptFunction creates a new ScriptFunction instance.

This constructor will use the runtime OperationCall.getArgumentFields() to source the parameterNames and parameterTypes required by the other constructors, but use expectedTypes to coerce the incoming types to before passing as parameters to the expression.

Parameters:

fieldDeclaration - of type Fields

script - of type String

expectedTypes - of type Class[]

ScriptTupleFunction

@ConstructorProperties(value={"fieldDeclaration","script","parameterNames","parameterTypes"})
public ScriptTupleFunction(Fields fieldDeclaration,
                                                      String script,
                                                      String[] parameterNames,
                                                      Class[] parameterTypes)

Constructor ScriptFunction creates a new ScriptFunction instance.

This constructor expects all parameter type names to be declared with their types. Positional parameters must be named the same as in the given script with the "$" sign prepended.

Parameters:

fieldDeclaration - of type Fields

script - of type String

parameterNames - of type String[]

parameterTypes - of type Class[]

Method Detail

getScript

public String getScript()

operate

public void operate(FlowProcess flowProcess,
                    FunctionCall<ScriptOperation.Context> functionCall)

Description copied from interface: Function

Method operate provides the implementation of this Function.

Specified by:

operate in interface Function<ScriptOperation.Context>

Parameters:

flowProcess - of type FlowProcess

functionCall - of type FunctionCall