com.saxonica.expr
Class JavaExtensionFunctionCall

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.FunctionCall
          com.saxonica.expr.JavaExtensionFunctionCall

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

public class JavaExtensionFunctionCall
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.Expression

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD

Constructor Summary

JavaExtensionFunctionCall()
Default constructor

Method Summary

PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
protected SequenceIterator	call(ValueRepresentation[] argValues, XPathContext context) Call an extension function previously identified using the bind() method.
void	checkArguments(ExpressionVisitor visitor) Method called by the expression parser when all arguments have been supplied
int	computeCardinality() Compute the static cardinality of this expression
Expression	copy() Copy an expression.
PJConverter[]	getArgumentConverters() Get the converters used to convert the arguments from XPath values to Java values
protected Object	getField(Field field, 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.
Class[]	getParameterTypes() Get the types of the arguments
JPConverter	getResultConverter() Get the converter used to convert the result from a Java object to an XPath value
Class	getReturnClass() Get the Java class of the value returned by the method
Class	getTargetClass() Get the class containing the method being called
AccessibleObject	getTargetMethod() Get the target method (or field, or constructor) being called
void	init(StructuredQName functionName, Class theClass, AccessibleObject object, Configuration config) Initialization: creates an ExtensionFunctionCall
protected Object	invokeConstructor(Constructor constructor, Object[] params) Invoke a constructor.
protected Object	invokeMethod(Method method, Object instance, Object[] params) Invoke a method.
boolean	isSubtreeExpression() Determine whether the expression can be evaluated without reference to the part of the context document outside the subtree rooted at the context node.
SequenceIterator	iterate(XPathContext context) Evaluate the function.
Expression	preEvaluate(ExpressionVisitor visitor) preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the external function might have side-effects and might use the context)
static String	toCamelCase(String name, boolean debug, PrintStream diag) Convert a name to camelCase (by removing hyphens and changing the following letter to capitals)
Expression	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Type-check the expression.

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

addExternalFunctionCallToPathMap, checkArgumentCount, equals, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString

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

adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getImplementationMethod, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

JavaExtensionFunctionCall

public JavaExtensionFunctionCall()

Default constructor

Method Detail

init

public void init(StructuredQName functionName,
                 Class theClass,
                 AccessibleObject object,
                 Configuration config)

Initialization: creates an ExtensionFunctionCall

Parameters:

functionName - the name 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

config - the Saxon configuration

preEvaluate

public Expression preEvaluate(ExpressionVisitor visitor)

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

Parameters:

visitor - an expression visitor

Returns:

the result of the early evaluation, or the original expression, or potentially a simplified expression

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException

Description copied from class: FunctionCall

Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.

Overrides:

typeCheck in class FunctionCall

Parameters:

visitor - an expression visitor

contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

checkArguments

public void checkArguments(ExpressionVisitor visitor)
                    throws XPathException

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

Specified by:

checkArguments in class FunctionCall

Parameters:

visitor - the expression visitor

Throws:

XPathException

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

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 Expression

Returns:

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

isSubtreeExpression

public boolean isSubtreeExpression()

Determine whether the expression can be evaluated without reference to the part of the context document outside the subtree rooted at the context node.

Overrides:

isSubtreeExpression in class Expression

Returns:

true if the expression has no dependencies on the context node, or if the only dependencies on the context node are downward selections using the self, child, descendant, attribute, and namespace axes.

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)

Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Overrides:

addToPathMap in class Expression

Parameters:

pathMap - the PathMap to which the expression should be added

pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added

Returns:

the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Evaluate the function.

Specified by:

iterate in interface SequenceIterable

Overrides:

iterate in class Expression

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 Class getTargetClass()

Get the class containing the method being called

Returns:

the class containing the target method

getTargetMethod

public AccessibleObject getTargetMethod()

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

Returns:

the target method, field, or constructor

getParameterTypes

public Class[] getParameterTypes()

Get the types of the arguments

Returns:

an array of classes representing the declared types of the arguments to the method or constructor

call

protected SequenceIterator call(ValueRepresentation[] argValues,
                                XPathContext context)
                         throws XPathException

Call an extension function previously identified using the bind() method. A subclass can override this method.

Parameters:

argValues - The values of the arguments

context - The XPath dynamic evaluation context

Returns:

The value returned by the extension function

Throws:

XPathException

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.

Specified by:

getItemType in class Expression

Parameters:

th - the type hierarchy cache

Returns:

the item type

computeCardinality

public int computeCardinality()

Description copied from class: Expression

Compute the static cardinality of this expression

Specified by:

computeCardinality in class Expression

Returns:

the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

getReturnClass

public Class getReturnClass()

Get the Java class of the value returned by the method

Returns:

the Java class of the value returned by the method

getArgumentConverters

public PJConverter[] getArgumentConverters()

Get the converters used to convert the arguments from XPath values to Java values

Returns:

an array of converters, one per argument

getResultConverter

public JPConverter getResultConverter()

Get the converter used to convert the result from a Java object to an XPath value

Returns:

the converter that is used

invokeConstructor

protected Object invokeConstructor(Constructor constructor,
                                   Object[] params)
                            throws InstantiationException,
                                   IllegalAccessException,
                                   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:

InstantiationException - if the invocation throws an InstantiationException

IllegalAccessException - if the invocation throws an IllegalAccessException

InvocationTargetException - if the invocation throws an InvocationTargetException (which happens when the constructor itself throws an exception)

invokeMethod

protected Object invokeMethod(Method method,
                              Object instance,
                              Object[] params)
                       throws IllegalAccessException,
                              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:

IllegalAccessException - if the invocation throws an IllegalAccessException

InvocationTargetException - if the invocation throws an InvocationTargetException (which happens when the method itself throws an exception)

getField

protected Object getField(Field field,
                          Object instance)
                   throws 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:

IllegalAccessException - if the invocation throws an IllegalAccessException

toCamelCase

public static String toCamelCase(String name,
                                 boolean debug,
                                 PrintStream diag)

Convert a name to camelCase (by removing hyphens and changing the following letter to capitals)

Parameters:

name - the name to be converted to camelCase

debug - true if tracing is required

diag - the output stream for diagnostic trace output

Returns:

the camelCased name