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
Fields inherited from interface cascading.operation.Operation |
ANY |
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 Fieldsscript
- 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 Fieldsscript
- of type StringexpectedTypes
- 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 Fieldsscript
- of type StringparameterNames
- of type String[]parameterTypes
- of type Class[]
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 FlowProcessfunctionCall
- of type FunctionCall
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