net.sf.saxon.functions

Class JavaExtensionLibrary

Implemented Interfaces:
FunctionLibrary, Serializable

public class JavaExtensionLibrary
extends java.lang.Object
implements FunctionLibrary

The JavaExtensionLibrary is a FunctionLibrary that binds XPath function calls to calls on Java methods (or constructors, or fields). It performs a mapping from the namespace URI of the function to the Java class (the mapping is partly table driven and partly algorithmic), and maps the local name of the function to the Java method, constructor, or field within the class. If the Java methods are polymorphic, then it tries to select the appropriate method based on the static types of the supplied arguments. Binding is done entirely at XPath compilation time.

Constructor Summary

JavaExtensionLibrary(Configuration config)
Construct a JavaExtensionLibrary and establish the default uri->class mappings.

Method Summary

protected int
atomicConversionPreference(int primitiveType, Class required)
Get the conversion preference from an XPath primitive atomic type to a Java class
Expression
bind(StructuredQName functionName, Expression[] staticArgs, StaticContext env)
Bind an extension function, given the URI and local parts of the function name, and the list of expressions supplied as arguments.
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
declareJavaClass(String uri, Class theClass)
Declare a mapping from a specific namespace URI to a Java class
boolean
isAvailable(StructuredQName functionName, int arity)
Test whether an extension function with a given name and arity is available.
protected void
setDefaultURIMappings()
Define initial mappings of "well known" namespace URIs to Java classes (this covers the Saxon and EXSLT extensions).

Constructor Details

JavaExtensionLibrary

public JavaExtensionLibrary(Configuration config)
Construct a JavaExtensionLibrary and establish the default uri->class mappings.
Parameters:
config - The Saxon configuration

Method Details

atomicConversionPreference

protected int atomicConversionPreference(int primitiveType,
                                         Class required)
Get the conversion preference from an XPath primitive atomic type to a Java class
Returns:
an integer indicating the relative preference for converting this primitive type to this Java class. A high number indicates a low preference. All values are in the range 50 to 100. For example, the conversion of an XPath String to StringValue is 50, while XPath String to java.lang.String is 51. The value -1 indicates that the conversion is not allowed.

bind

public Expression bind(StructuredQName functionName,
                       Expression[] staticArgs,
                       StaticContext env)
            throws XPathException
Bind an extension function, given the URI and local parts of the function name, and the list of expressions supplied as arguments. This method is called at compile time.
Specified by:
bind in interface FunctionLibrary
Parameters:
functionName - the qualified name of the function being called
staticArgs - The expressions supplied statically in 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.
env -
Returns:
An object representing the extension function to be called, if one is found; null if no extension function was found matching the required name, arity, or signature.

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.

declareJavaClass

public void declareJavaClass(String uri,
                             Class theClass)
Declare a mapping from a specific namespace URI to a Java class
Parameters:
uri - the namespace URI of the function name
theClass - the Java class that implements the functions in this namespace

isAvailable

public boolean isAvailable(StructuredQName functionName,
                           int arity)
Test whether an extension 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 qualified name of the extension 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

setDefaultURIMappings

protected void setDefaultURIMappings()
Define initial mappings of "well known" namespace URIs to Java classes (this covers the Saxon and EXSLT extensions). The method is protected so it can be overridden in a subclass.