net.sf.saxon.functions

Class ExtensionFunctionCall

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, 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

Field Summary

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

argument

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

ExtensionFunctionCall()
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.
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
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.
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)

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

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

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

ExtensionFunctionCall

public ExtensionFunctionCall()
Default constructor

Method Details

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 interface Expression
Parameters:
pathMap - the PathMap to which the expression should be added
pathMapNodeSet -
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.

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

checkArguments

public void checkArguments(ExpressionVisitor visitor)
            throws XPathException
Method called by the expression parser when all arguments have been supplied
Overrides:
checkArguments in interface FunctionCall

computeCardinality

public int computeCardinality()
Compute the static cardinality of this expression
Overrides:
computeCardinality in interface Expression

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

getField

protected Object getField(Field field,
                          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

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 interface Expression

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.

Overrides:
getItemType in interface Expression
Parameters:
th - the type hierarchy cache
Returns:
the item type

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

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

invokeConstructor

protected Object invokeConstructor(Constructor constructor,
                                   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

invokeMethod

protected Object invokeMethod(Method method,
                              Object instance,
                              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

iterate

public SequenceIterator iterate(XPathContext context)
            throws XPathException
Evaluate the function.
Specified by:
iterate in interface SequenceIterable
Overrides:
iterate in interface 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.

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 interface FunctionCall
Parameters:
visitor - an expression visitor

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