Package 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:

Callable, ExportAgent, Locatable, IdentityComparable, Traceable

public class JavaExtensionFunctionCall
extends FunctionCall
implements Callable

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.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor	Description
JavaExtensionFunctionCall()	Default constructor

Method Summary

Modifier and Type	Method	Description
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)	Add a representation of this expression to a PathMap.
boolean	adjustRequiredType(JavaExternalObjectType requiredType)	When a call to a Java extension function appears in a context where there the required type is a Java external object (typically an xsl:variable with a declared type, or as an argument to another Java extension function), notify this required type so that the process of converting the result to an XDM value can be short-circuited.
static Sequence	applyFunctionConversionRules(Sequence suppliedValue, SequenceType requiredType, StructuredQName functionName, int argPosition, XPathContext context)	Utility method available for use in called extension functions to check that a supplied argument conforms to a required type, and perform conversion using the function conversion rules if not
Sequence	call(XPathContext context, Sequence[] argValues)	Call an extension function previously identified using the bind() method.
protected int	computeCardinality()	Compute the static cardinality of this expression
Expression	copy(RebindingMap rebindings)	Copy an expression.
void	export(ExpressionPresenter out)	Diagnostic print of expression structure.
PJConverter[]	getArgumentConverters()	Get the converters used to convert the arguments from XPath values to Java values
java.lang.String	getExpressionName()	Get a name identifying the kind of expression, in terms meaningful to a user.
protected java.lang.Object	getField(java.lang.reflect.Field field, java.lang.Object instance)	Access a field.
StructuredQName	getFunctionName()	Get the qualified of the function being called
int	getIntrinsicDependencies()	Determine which aspects of the context the expression depends on.
ItemType	getItemType()	Determine the data type of the expression, if possible.
java.lang.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
java.lang.Class	getReturnClass()	Get the Java class of the value returned by the method
java.lang.Class	getTargetClass()	Get the class containing the method being called
Function	getTargetFunction(XPathContext context)	Get the target function to be called
java.lang.reflect.AccessibleObject	getTargetMethod()	Get the target method (or field, or constructor) being called
void	init(StructuredQName functionName, 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.
boolean	isNodeCheckRequired()	Ask whether the result needs to be checked to ensure it contains no nodes from the wrong Configuration
boolean	isReturnVoidAsThis()
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)
void	prepareForDynamicCall(Configuration config)
static java.lang.String	toCamelCase(java.lang.String name, boolean debug, Logger diag)	Convert a name to camelCase (by removing hyphens and changing the following letter to capitals)
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	Type-check the expression.

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

addExternalFunctionCallToPathMap, checkArgumentCount, checkArguments, checkFunctionCall, computeHashCode, equals, evaluateArguments, getArg, getArguments, getArity, getDisplayName, getImplementationMethod, getNetCost, getOperanda, operands, optimize, pluralArguments, preEvaluateIfConstant, setArg, setArguments, setOperanda, setOperanda, simplifyArguments, toShortString, toString

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

adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Constructor Detail

JavaExtensionFunctionCall

public JavaExtensionFunctionCall()

Default constructor

Method Detail

init

public void init(StructuredQName functionName,
                 java.lang.Class theClass,
                 java.lang.reflect.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 Configuration

getExpressionName

public java.lang.String getExpressionName()

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class FunctionCall

Returns:

a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

getFunctionName

public StructuredQName getFunctionName()

Get the qualified of the function being called

Specified by:

getFunctionName in class FunctionCall

Returns:

the qualified name

getTargetFunction

public Function getTargetFunction(XPathContext context)
                           throws XPathException

Get the target function to be called

Specified by:

getTargetFunction in class FunctionCall

Parameters:

context - the dynamic evaluation context

Returns:

the target function

Throws:

XPathException - if the target function cannot be determined

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,
                            ContextItemStaticInfo contextInfo)
                     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

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

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)

prepareForDynamicCall

public void prepareForDynamicCall(Configuration config)
                           throws XPathException

Throws:

XPathException

adjustRequiredType

public boolean adjustRequiredType(JavaExternalObjectType requiredType)
                           throws XPathException

When a call to a Java extension function appears in a context where there the required type is a Java external object (typically an xsl:variable with a declared type, or as an argument to another Java extension function), notify this required type so that the process of converting the result to an XDM value can be short-circuited.

Overrides:

adjustRequiredType in class FunctionCall

Parameters:

requiredType - the required type of the result of the function, determined by the context in which the function call appears

Returns:

Ok if the type has been successfully adjusted

Throws:

XPathException - if the required return type is incompatible with the type actually returned by the Java method

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - variables to be re-bound

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.

isNodeCheckRequired

public boolean isNodeCheckRequired()

Ask whether the result needs to be checked to ensure it contains no nodes from the wrong Configuration

Returns:

true if the result needs to be checked

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Evaluate the function.

Overrides:

iterate in class FunctionCall

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

Returns:

the class containing the target method

getTargetMethod

public java.lang.reflect.AccessibleObject getTargetMethod()

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

Returns:

the target method, field, or constructor

getParameterTypes

public java.lang.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

public Sequence call(XPathContext context,
                     Sequence[] argValues)
              throws XPathException

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

Specified by:

call in interface Callable

Parameters:

context - The XPath dynamic evaluation context

argValues - The values of the arguments

Returns:

The value returned by the extension function

Throws:

XPathException - if a dynamic error occurs during the evaluation of the expression

getItemType

public ItemType getItemType()

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

Returns:

the item type

computeCardinality

protected 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. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

getReturnClass

public java.lang.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 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

applyFunctionConversionRules

public static Sequence applyFunctionConversionRules(Sequence suppliedValue,
                                                    SequenceType requiredType,
                                                    StructuredQName functionName,
                                                    int argPosition,
                                                    XPathContext context)
                                             throws XPathException

Utility method available for use in called extension functions to check that a supplied argument conforms to a required type, and perform conversion using the function conversion rules if not

Parameters:

suppliedValue - the value supplied by the caller

requiredType - the type required for the argument

functionName - the name of the function (for diagnostics)

argPosition - the ordinal position of the argument being checked in the XPath function call, starting at 0 for the first argument

context - the XPath dynamic context

Returns:

the result of applying the function conversion rules (with XPath 1.0 compatibility mode set to false)

Throws:

XPathException - if type checking fails

toCamelCase

public static java.lang.String toCamelCase(java.lang.String name,
                                           boolean debug,
                                           Logger 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

isReturnVoidAsThis

public boolean isReturnVoidAsThis()

export

public void export(ExpressionPresenter out)
            throws XPathException

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in interface ExportAgent

Overrides:

export in class FunctionCall

Parameters:

out - the destination of the output

Throws:

XPathException - if the export fails, for example if an expression is found that won't work in the target environment.