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## 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

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Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.