Class ExtensionFunctionCall

All Implemented Interfaces:
Serializable, SourceLocator, Container, Expression, InstructionInfoProvider

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(int nameCode, Class theClass, AccessibleObject object, Configuration config)
      Initialization: creates an ExtensionFunctionCall
      Parameters:
      nameCode - the name code 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
    • preEvaluate

      public Expression preEvaluate(StaticContext env)
      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
    • checkArguments

      public void checkArguments(StaticContext env) throws XPathException
      Method called by the expression parser when all arguments have been supplied
      Specified by:
      checkArguments in class FunctionCall
      Throws:
      XPathException
    • 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 ComputedExpression
      Returns:
      a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Evaluate the function.
      Specified by:
      iterate in interface Expression
      Overrides:
      iterate in class ComputedExpression
      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
    • getTargetMethod

      public AccessibleObject getTargetMethod()
      Get the target method (or field, or constructor) being called
    • 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.

      Parameters:
      th -
      Returns:
      the item type
    • computeCardinality

      public int computeCardinality()
      Specified by:
      computeCardinality in class ComputedExpression
    • usesFocus

      public boolean usesFocus()
      Determine whether this method uses the focus. True if the first argument is of type XPathContext.
    • 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