Class ExtensionFunctionCall

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

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:
  • Constructor Details

    • ExtensionFunctionCall

      public ExtensionFunctionCall()
      Default constructor
  • Method Details

    • 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
    • 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