net.sf.saxon.query
Class XQueryFunctionLibrary

java.lang.Object
  net.sf.saxon.query.XQueryFunctionLibrary

All Implemented Interfaces:

Serializable, FunctionLibrary, XQueryFunctionBinder

public class XQueryFunctionLibrary
extends Object
implements FunctionLibrary, XQueryFunctionBinder

An XQueryFunctionLibrary is a function library containing all the user-defined functions available for use within a particular XQuery module: that is, the functions declared in that module, and the functions imported from other modules. It also contains (transiently during compilation) a list of function calls within the module that have not yet been bound to a specific function declaration.

See Also:

Serialized Form

Constructor Summary

XQueryFunctionLibrary(Configuration config)
Create an XQueryFunctionLibrary

Method Summary

Expression	bind(StructuredQName functionName, Expression[] arguments, StaticContext env) Identify a (namespace-prefixed) function appearing in the expression.
FunctionLibrary	copy() This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.
void	declareFunction(XQueryFunction function) Register a user-defined XQuery function
void	explainGlobalFunctions(ExpressionPresenter out) Output "explain" information about each declared function
Configuration	getConfiguration() Get the Configuration options
XQueryFunction	getDeclaration(StructuredQName functionName, Expression[] staticArgs) Get the function declaration corresponding to a given function name and arity
XQueryFunction	getDeclarationByKey(String functionKey) Get the function declaration corresponding to a given function name and arity, supplied in the form "{uri}local/arity"
Iterator	getFunctionDefinitions() Get an iterator over the Functions defined in this module
UserFunction	getUserDefinedFunction(String uri, String localName, int arity) Get the function with a given name and arity.
boolean	isAvailable(StructuredQName functionName, int arity) Test whether a function with a given name and arity is available.
void	setConfiguration(Configuration config) Set the Configuration options

Methods inherited from class java.lang.Object

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

Constructor Detail

XQueryFunctionLibrary

public XQueryFunctionLibrary(Configuration config)

Create an XQueryFunctionLibrary

Parameters:

config - the Saxon configuration

Method Detail

setConfiguration

public void setConfiguration(Configuration config)

Set the Configuration options

Parameters:

config - the Saxon configuration

getConfiguration

public Configuration getConfiguration()

Get the Configuration options

Returns:

the Saxon configuration

declareFunction

public void declareFunction(XQueryFunction function)
                     throws XPathException

Register a user-defined XQuery function

Parameters:

function - the function to be registered

Throws:

XPathException - if there is an existing function with the same name and arity

isAvailable

public boolean isAvailable(StructuredQName functionName,
                           int arity)

Test whether a function with a given name and arity is available. This supports the function-available() function in XSLT. This method may be called either at compile time or at run time.

Specified by:

isAvailable in interface FunctionLibrary

Parameters:

functionName - the QName identifying the function

arity - The number of arguments. This is set to -1 in the case of the single-argument function-available() function; in this case the method should return true if there is some

Returns:

true if a function of this name and arity is available for calling.

bind

public Expression bind(StructuredQName functionName,
                       Expression[] arguments,
                       StaticContext env)
                throws XPathException

Identify a (namespace-prefixed) function appearing in the expression. This method is called by the XQuery parser to resolve function calls found within the query.

Note that a function call may appear earlier in the query than the definition of the function to which it is bound. Unlike XSLT, we cannot search forwards to find the function definition. Binding of function calls is therefore a two-stage process; at the time the function call is parsed, we simply register it as pending; subsequently at the end of query parsing all the pending function calls are resolved. Another consequence of this is that we cannot tell at the time a function call is parsed whether it is a call to an internal (XSLT or XQuery) function or to an extension function written in Java.

Specified by:

bind in interface FunctionLibrary

Parameters:

functionName - the QName of the function being called

arguments - The expressions supplied statically in arguments to the function call. The length of this array represents the arity of the function. The intention is that the static type of the arguments (obtainable via getItemType() and getCardinality()) may be used as part of the binding algorithm. In some cases it may be possible for the function to be pre-evaluated at compile time, for example if these expressions are all constant values.

The conventions of the XPath language demand that the results of a function depend only on the values of the expressions supplied as arguments, and not on the form of those expressions. For example, the result of f(4) is expected to be the same as f(2+2). The actual expression is supplied here to enable the binding mechanism to select the most efficient possible implementation (including compile-time pre-evaluation where appropriate).

env - The static context of the function call

Returns:

an Expression representing the function call. This will normally be a FunctionCall, but it may be rewritten as some other expression.

Throws:

XPathException - if the function call is invalid, either because it is an unprefixed call to a non-system function, or because it is calling a system function that is available in XSLT only. A prefixed function call that cannot be recognized at this stage is assumed to be a forwards reference, and is bound later when bindUnboundFunctionCalls() is called.

getDeclaration

public XQueryFunction getDeclaration(StructuredQName functionName,
                                     Expression[] staticArgs)

Get the function declaration corresponding to a given function name and arity

Specified by:

getDeclaration in interface XQueryFunctionBinder

Parameters:

functionName - the name of the function as a QName

staticArgs - the expressions supplied as arguments in the function call (typically, we only need to know the number of arguments)

Returns:

the XQueryFunction if there is one, or null if not.

getDeclarationByKey

public XQueryFunction getDeclarationByKey(String functionKey)

Get the function declaration corresponding to a given function name and arity, supplied in the form "{uri}local/arity"

Parameters:

functionKey - a string in the form "{uri}local/arity" identifying the required function

Returns:

the XQueryFunction if there is one, or null if not.

getFunctionDefinitions

public Iterator getFunctionDefinitions()

Get an iterator over the Functions defined in this module

Returns:

an Iterator, whose items are XQueryFunction objects. It returns all function known to this module including those imported from elsewhere; they can be distinguished by their namespace.

explainGlobalFunctions

public void explainGlobalFunctions(ExpressionPresenter out)

Output "explain" information about each declared function

Parameters:

out - the ExpressionPresenter that renders the output

getUserDefinedFunction

public UserFunction getUserDefinedFunction(String uri,
                                           String localName,
                                           int arity)

Get the function with a given name and arity. This method is provided so that XQuery functions can be called directly from a Java application. Note that there is no type checking or conversion of arguments when this is done: the arguments must be provided in exactly the form that the function signature declares them.

Parameters:

uri - the uri of the function name

localName - the local part of the function name

arity - the number of arguments.

Returns:

the function identified by the URI, local name, and arity; or null if there is no such function

copy

public FunctionLibrary copy()

This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.

Specified by:

copy in interface FunctionLibrary

Returns:

a copy of this function library. This must be an instance of the original class.