net.sf.saxon.functions

Class ExtensionFunctionCall

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

Constructor Summary
ExtensionFunctionCall()
Default constructor
Method Summary
voidcheckArguments(StaticContext env)
Method called by the expression parser when all arguments have been supplied
intcomputeCardinality()
protected ObjectgetField(Field field, Object instance)
Access a field.
intgetIntrinsicDependencies()
Determine which aspects of the context the expression depends on.
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression, if possible.
ClassgetTargetClass()
Get the class containing the method being called
AccessibleObjectgetTargetMethod()
Get the target method (or field, or constructor) being called
voidinit(int nameCode, Class theClass, AccessibleObject object, Configuration config)
Initialization: creates an ExtensionFunctionCall
protected ObjectinvokeConstructor(Constructor constructor, Object[] params)
Invoke a constructor.
protected ObjectinvokeMethod(Method method, Object instance, Object[] params)
Invoke a method.
SequenceIteratoriterate(XPathContext context)
Evaluate the function.
ExpressionpreEvaluate(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)
booleanusesFocus()
Determine whether this method uses the focus.

Constructor Detail

ExtensionFunctionCall

public ExtensionFunctionCall()
Default constructor

Method Detail

checkArguments

public void checkArguments(StaticContext env)
Method called by the expression parser when all arguments have been supplied

computeCardinality

public int computeCardinality()

getField

protected Object getField(Field field, Object instance)
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

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

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

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

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

invokeConstructor

protected Object invokeConstructor(Constructor constructor, Object[] params)
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)
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)

iterate

public SequenceIterator iterate(XPathContext context)
Evaluate the function.

Parameters: context The context in which the function is to be evaluated

Returns: a Value representing the result of the function.

Throws: net.sf.saxon.trans.XPathException if the function cannot be evaluated.

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)

usesFocus

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