com.saxonica.config

Class JavaExtensionLibrary

java.lang.Object

com.saxonica.config.JavaExtensionLibrary

All Implemented Interfaces:

FunctionLibrary

public class JavaExtensionLibrary
extends 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

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
protected int	atomicConversionPreference(int primitiveType, Class required) Get the conversion preference from an XPath primitive atomic type to a Java class
Expression	bind(SymbolicName symbolicName, 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
void	declareJavaClass(String uri, String className) Declare a mapping from a specific namespace URI to a Java class.
JavaExtensionFunctionFactory	getExtensionFunctionFactory() Get the ExtensionFunctionFactory used by this extension library.
protected Class	getExternalJavaClass(String uri, String localName, boolean debug) Get an external Java class corresponding to a given namespace URI, if there is one.
Function	getFunctionItem(SymbolicName functionName, StaticContext staticContext) Test whether a function with a given name and arity is available; if so, return a function item that can be dynamically called.
protected String	getMethodNameFromLocalName(String uri, String localName, boolean debug) Get the Java method/field name from the local name used in the function call.
boolean	isAvailable(SymbolicName functionName) Test whether a function with a given name and arity is available
boolean	isStrictJavaUriFormat() Ask whether only the strict "java:" URI format is to be recognized.
void	setExtensionFunctionFactory(JavaExtensionFunctionFactory factory) Set the ExtensionFunctionFactory to be used by this extension library.
void	setStrictJavaUriFormat(boolean strict) Say that only the strict "java:" URI format is to be recognized.

Methods inherited from class java.lang.Object

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

Constructor Detail

JavaExtensionLibrary

public JavaExtensionLibrary(ProfessionalConfiguration config)

Construct a JavaExtensionLibrary and establish the default uri->class mappings.

Parameters:

config - The Saxon configuration

Method Detail

setExtensionFunctionFactory

public void setExtensionFunctionFactory(JavaExtensionFunctionFactory factory)

Set the ExtensionFunctionFactory to be used by this extension library.

Parameters:

factory - This must be an instanceof JavaExtensionFunctionFactory

getExtensionFunctionFactory

public JavaExtensionFunctionFactory getExtensionFunctionFactory()

Get the ExtensionFunctionFactory used by this extension library.

Returns:

the factory, which will always be an instanceof JavaExtensionFunctionFactory

isStrictJavaUriFormat

public boolean isStrictJavaUriFormat()

Ask whether only the strict "java:" URI format is to be recognized. The default is "true": the value false can be set for backwards compatibility with releases before Saxon 9.2

Returns:

true if only the strict format is recognized

setStrictJavaUriFormat

public void setStrictJavaUriFormat(boolean strict)

Say that only the strict "java:" URI format is to be recognized. The default is "true": the value false can be set for backwards compatibility with releases before Saxon 9.2

Parameters:

strict - true if only the strict format is recognized

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

declareJavaClass

public void declareJavaClass(String uri,
                    String className)

Declare a mapping from a specific namespace URI to a Java class. The specified Java class will be loaded only if an extension function using this URI is actually encountered; the reference will fail if the class cannot (then) be loaded.

Parameters:

uri - the namespace URI of the function name

className - the name of the Java class that implements the functions in this namespace

getFunctionItem

public Function getFunctionItem(SymbolicName functionName,
                       StaticContext staticContext)
                         throws XPathException

Test whether a function with a given name and arity is available; if so, return a function item that can be dynamically called.

This supports the function-lookup() function in XPath 3.0.

Specified by:

getFunctionItem in interface FunctionLibrary

Parameters:

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

Returns:

if a function of this name and arity is available for calling, then a corresponding function item; or null if the function does not exist

Throws:

XPathException - in the event of certain errors, for example attempting to get a function that is private

isAvailable

public boolean isAvailable(SymbolicName functionName)

Test whether a function with a given name and arity is available

This supports the function-available() function in XSLT.

Specified by:

isAvailable in interface FunctionLibrary

Parameters:

functionName - the qualified name of the function being called

Returns:

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

bind

public Expression bind(SymbolicName symbolicName,
              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:

symbolicName - the qualified name and arity 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 - the static context

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.

Throws:

XPathException - if a function is found with the required name and arity, but the implementation of the function cannot be loaded or used; or if an error occurs while searching for the function.

atomicConversionPreference

protected int atomicConversionPreference(int primitiveType,
                             Class required)

Get the conversion preference from an XPath primitive atomic type to a Java class

Parameters:

primitiveType - integer code identifying the XPath primitive type, for example StandardNames.XS_STRING or StandardNames.XS_STRING

required - The Java Class named in the method signature

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 String is 51. The value -1 indicates that the conversion is not allowed.

getExternalJavaClass

protected Class getExternalJavaClass(String uri,
                         String localName,
                         boolean debug)

Get an external Java class corresponding to a given namespace URI, if there is one. The method is protected so it can be overridden in a user-defined subclass.

Parameters:

uri - The namespace URI corresponding to the prefix used in the function call.

localName - The local name of the function, in case this contributes to determining the class

debug - true if tracing information should be output

Returns:

the Java class name if a suitable class exists, otherwise return null.

getMethodNameFromLocalName

protected String getMethodNameFromLocalName(String uri,
                                String localName,
                                boolean debug)

Get the Java method/field name from the local name used in the function call. This may be overridden in a subclass. The default implementation is as follows: if the URI is NamespaceConstant.JAVA_TYPE, the method name is that part of the local name appearing after the last dot/period. Otherwise, it is the local-name, converted to camel-case by removing hyphens and converting any character immediately following a hyphen to upper case.

Parameters:

uri - the namespace URI used in the function call

localName - the local name used in the function call

debug - true if tracing is requested

Returns:

the local name of the method or field

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.