net.sf.saxon.s9api

Interface ExtensionFunction

public interface ExtensionFunction

This is an interface for simple external/extension functions. Users can implement this interface and register the implementation with the Processor; the function will then be available for calling from all queries, stylesheets, and XPath expressions compiled under this Processor.

Extension functions implemented using this interface are expected to be free of side-effects, and to have no dependencies on the static or dynamic context. A richer interface for extension functions is provided via the ExtensionFunctionDefinition class.

Method Summary

Modifier and Type	Method and Description
XdmValue	call(XdmValue[] arguments) Call the function.
SequenceType[]	getArgumentTypes() Declare the types of the arguments
QName	getName() Return the name of the external function
default SequenceType	getResultType() Declare the result type of the external function.

Method Detail

getName

QName getName()

Return the name of the external function

Returns:

the name of the function, as a QName.

getResultType

default SequenceType getResultType()

Declare the result type of the external function. The default for this method returns the type item()*. Returning a more precise type enables Saxon to do better static type checking, and to avoid run-time conversions.

Returns:

the result type of the external function. Saxon will check at run-time that the actual value returned by the call(net.sf.saxon.s9api.XdmValue[]) method is an instance of this type.

getArgumentTypes

SequenceType[] getArgumentTypes()

Declare the types of the arguments

Returns:

an array of SequenceType objects, one for each argument to the function, representing the expected types of the arguments

call

XdmValue call(XdmValue[] arguments)
       throws SaxonApiException

Call the function. The implementation of this method represents the body of the external function.

Parameters:

arguments - the arguments, as supplied in the XPath function call. These will always be of the declared types. Arguments are converted to the required types according to the standard XPath function conversion rules - for example, if the expected type is atomic and a node is supplied in the call, the node will be atomized

Returns:

the result of the function. This must be an instance of the declared return type; if it is not, a dynamic error will be reported

Throws:

SaxonApiException - can be thrown if the implementation of the function detects a dynamic error