net.sf.saxon.functions
Class ExtensionFunctionCall

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.expr.FunctionCall
          net.sf.saxon.functions.ExtensionFunctionCall

All Implemented Interfaces:

Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

public class ExtensionFunctionCall

extends FunctionCall

This class acts as a container for an extension function defined to call a method in a user-defined class.

Note that the binding of an XPath function call to a Java method is done in class JavaExtensionLibrary

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.FunctionCall

argument

Fields inherited from class net.sf.saxon.expr.ComputedExpression

locationId, staticProperties

Fields inherited from interface net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

ExtensionFunctionCall()
Default constructor

Method Summary

void	checkArguments(StaticContext env) Method called by the expression parser when all arguments have been supplied
int	computeCardinality()
protected java.lang.Object	getField(java.lang.reflect.Field field, java.lang.Object instance) Access a field.
int	getIntrinsicDependencies() Determine which aspects of the context the expression depends on.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the expression, if possible.
java.lang.Class	getTargetClass() Get the class containing the method being called
java.lang.reflect.AccessibleObject	getTargetMethod() Get the target method (or field, or constructor) being called
void	init(int nameCode, java.lang.Class theClass, java.lang.reflect.AccessibleObject object, Configuration config) Initialization: creates an ExtensionFunctionCall
protected java.lang.Object	invokeConstructor(java.lang.reflect.Constructor constructor, java.lang.Object[] params) Invoke a constructor.
protected java.lang.Object	invokeMethod(java.lang.reflect.Method method, java.lang.Object instance, java.lang.Object[] params) Invoke a method.
SequenceIterator	iterate(XPathContext context) Evaluate the function.
Expression	preEvaluate(StaticContext env) preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the external function might have side-effects and might use the context)
boolean	usesFocus() Determine whether this method uses the focus.

Methods inherited from class net.sf.saxon.expr.FunctionCall

checkArgumentCount, display, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, optimize, promote, setArguments, setFunctionNameCode, simplify, simplifyArguments, typeCheck

Methods inherited from class net.sf.saxon.expr.ComputedExpression

adoptChildExpression, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, suppressValidation, typeError, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

ExtensionFunctionCall

public ExtensionFunctionCall()

Default constructor

Method Detail

init

public void init(int nameCode,
                 java.lang.Class theClass,
                 java.lang.reflect.AccessibleObject object,
                 Configuration config)

Initialization: creates an ExtensionFunctionCall

Parameters:

nameCode - the name code of the function, for display purposes

theClass - the Java class containing the method to be called

object - the method, field, or constructor of the Java class to be called

preEvaluate

public Expression preEvaluate(StaticContext env)

preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the external function might have side-effects and might use the context)

Overrides:

preEvaluate in class FunctionCall

checkArguments

public void checkArguments(StaticContext env)
                    throws XPathException

Method called by the expression parser when all arguments have been supplied

Specified by:

checkArguments in class FunctionCall

Throws:

XPathException

getIntrinsicDependencies

public int getIntrinsicDependencies()

Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE

Overrides:

getIntrinsicDependencies in class ComputedExpression

Returns:

a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Evaluate the function.

Specified by:

iterate in interface Expression

Overrides:

iterate in class ComputedExpression

Parameters:

context - The context in which the function is to be evaluated

Returns:

a Value representing the result of the function.

Throws:

XPathException - if the function cannot be evaluated.

getTargetClass

public java.lang.Class getTargetClass()

Get the class containing the method being called

getTargetMethod

public java.lang.reflect.AccessibleObject getTargetMethod()

Get the target method (or field, or constructor) being called

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the expression, if possible. All expressions return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method will always return a result, though it may be the best approximation that is available at the time.

Parameters:

th -

Returns:

the item type

computeCardinality

public int computeCardinality()

Specified by:

computeCardinality in class ComputedExpression

usesFocus

public boolean usesFocus()

Determine whether this method uses the focus. True if the first argument is of type XPathContext.

invokeConstructor

protected java.lang.Object invokeConstructor(java.lang.reflect.Constructor constructor,
                                             java.lang.Object[] params)
                                      throws java.lang.InstantiationException,
                                             java.lang.IllegalAccessException,
                                             java.lang.reflect.InvocationTargetException

Invoke a constructor. This method is provided separately so that it can be refined in a subclass. For example, a subclass might perform tracing of calls, or might trap exceptions.

Parameters:

constructor - The constructor to be invoked

params - The parameters to be passed to the constructor

Returns:

The object returned by the constructor

Throws:

java.lang.InstantiationException - if the invocation throws an InstantiationException

java.lang.IllegalAccessException - if the invocation throws an IllegalAccessException

java.lang.reflect.InvocationTargetException - if the invocation throws an InvocationTargetException (which happens when the constructor itself throws an exception)

invokeMethod

protected java.lang.Object invokeMethod(java.lang.reflect.Method method,
                                        java.lang.Object instance,
                                        java.lang.Object[] params)
                                 throws java.lang.IllegalAccessException,
                                        java.lang.reflect.InvocationTargetException

Invoke a method. This method is provided separately so that it can be refined in a subclass. For example, a subclass might perform tracing of calls, or might trap exceptions.

Parameters:

method - The method to be invoked

instance - The object on which the method is to be invoked. This is set to null if the method is static.

params - The parameters to be passed to the method

Returns:

The object returned by the method

Throws:

java.lang.IllegalAccessException - if the invocation throws an IllegalAccessException

java.lang.reflect.InvocationTargetException - if the invocation throws an InvocationTargetException (which happens when the method itself throws an exception)

getField

protected java.lang.Object getField(java.lang.reflect.Field field,
                                    java.lang.Object instance)
                             throws java.lang.IllegalAccessException

Access a field. This method is provided separately so that it can be refined in a subclass. For example, a subclass might perform tracing of calls, or might trap exceptions.

Parameters:

field - The field to be retrieved

instance - The object whose field is to be retrieved. This is set to null if the field is static.

Returns:

The value of the field

Throws:

java.lang.IllegalAccessException - if the invocation throws an IllegalAccessException