public class OnDemandFunctionSet extends java.lang.Object implements FunctionLibrary
This mechanism is currently used for the SQL function library, because the implementations of these functions are shipped in a separate JAR file (and this is not available on .NET). If the target function library cannot be loaded, the relevant functions will be reported as being not available.
|Constructor and Description|
|Modifier and Type||Method and Description|
Bind a function, given the URI and local parts of the function name, and the list of expressions supplied as arguments.
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.
Test whether a function with a given name and arity is available; if so, return a function item that can be dynamically called.
Test whether a function with a given name and arity is available
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
public OnDemandFunctionSet(Configuration config, java.lang.String namespace, java.lang.String libraryClass)
public boolean isAvailable(SymbolicName.F functionName, int languageLevel)
This supports the function-available() function in XSLT.
functionName- the qualified name of the function being called, together with its arity. For legacy reasons, the arity may be set to -1 to mean any arity will do
languageLevel- the XPath language level (times 10, e.g. 31 for XPath 3.1)
public Expression bind(SymbolicName.F functionName, Expression staticArgs, StaticContext env, java.util.List<java.lang.String> reasons)
functionName- the QName of the function being called
staticArgs- May be null; if present, the length of the array must match the value of arity. Contains the expressions supplied statically in arguments to the function call. 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
reasons- If no matching function is found by the function library, it may add a diagnostic explanation to this list explaining why none of the available functions could be used.
public FunctionLibrary copy()
public Function getFunctionItem(SymbolicName.F functionName, StaticContext staticContext) throws XPathException
This supports the function-lookup() function in XPath 3.0.
functionName- the qualified name of the function being called
staticContext- the static context to be used by the function, in the event that it is a system function with dependencies on the static context
XPathException- in the event of certain errors, for example attempting to get a function that is private
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