org.apache.xalan.extensions
Class ExtensionHandler

java.lang.Object
  org.apache.xalan.extensions.ExtensionHandler

Direct Known Subclasses:

ExtensionHandlerExsltFunction, ExtensionHandlerGeneral, ExtensionHandlerJava

public abstract class ExtensionHandler

extends Object

Abstract base class for handling an extension namespace for XPath. Provides functions to test a function's existence and call a function. Also provides functions for calling an element and testing for an element's existence.

Author:

Sanjiva Weerawarana (sanjiva@watson.ibm.com)

Field Summary

private static Method	getCCL the Method object for getContextClassLoader
protected String	m_namespaceUri uri of the extension namespace
protected String	m_scriptLang scripting language of implementation
private static Object[]	NO_OBJS a zero length Object array used in getClassForName()

Constructor Summary

protected

ExtensionHandler(String namespaceUri, String scriptLang) Construct a new extension namespace handler given all the information needed.

Method Summary

abstract Object	callFunction(String funcName, Vector args, Object methodKey, ExpressionContext exprContext) Process a call to a function.
static Class	getClassForName(String className) Replacement for Class.forName.
abstract boolean	isElementAvailable(String element) Tests whether a certain element name is known within this namespace.
abstract boolean	isFunctionAvailable(String function) Tests whether a certain function name is known within this namespace.
abstract void	processElement(String localPart, ElemTemplateElement element, TransformerImpl transformer, Stylesheet stylesheetTree, Object methodKey) Process a call to this extension namespace via an element.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

m_namespaceUri

protected String m_namespaceUri

uri of the extension namespace

m_scriptLang

protected String m_scriptLang

scripting language of implementation

NO_OBJS

private static final Object[] NO_OBJS

a zero length Object array used in getClassForName()

getCCL

private static Method getCCL

the Method object for getContextClassLoader

Constructor Detail

ExtensionHandler

protected ExtensionHandler(String namespaceUri,
                           String scriptLang)

Construct a new extension namespace handler given all the information needed.

Parameters:

namespaceUri - the extension namespace URI that I'm implementing

scriptLang - language of code implementing the extension

Method Detail

getClassForName

public static Class getClassForName(String className)
                             throws ClassNotFoundException

Replacement for Class.forName. This method loads a class using the context class loader if we're running under Java2 or higher. If we're running under Java1, this method just uses Class.forName to load the class.

Parameters:

className - Name of the class to load

Throws:

ClassNotFoundException

isFunctionAvailable

public abstract boolean isFunctionAvailable(String function)

Tests whether a certain function name is known within this namespace.

Parameters:

function - name of the function being tested

Returns:

true if its known, false if not.

isElementAvailable

public abstract boolean isElementAvailable(String element)

Tests whether a certain element name is known within this namespace.

Parameters:

element - Name of element to check

Returns:

true if its known, false if not.

callFunction

public abstract Object callFunction(String funcName,
                                    Vector args,
                                    Object methodKey,
                                    ExpressionContext exprContext)
                             throws javax.xml.transform.TransformerException

Process a call to a function.

Parameters:

funcName - Function name.

args - The arguments of the function call.

methodKey - A key that uniquely identifies this class and method call.

exprContext - The context in which this expression is being executed.

Returns:

the return value of the function evaluation.

Throws:

javax.xml.transform.TransformerException - if parsing trouble

processElement

public abstract void processElement(String localPart,
                                    ElemTemplateElement element,
                                    TransformerImpl transformer,
                                    Stylesheet stylesheetTree,
                                    Object methodKey)
                             throws javax.xml.transform.TransformerException,
                                    IOException

Process a call to this extension namespace via an element. As a side effect, the results are sent to the TransformerImpl's result tree.

Parameters:

localPart - Element name's local part.

element - The extension element being processed.

transformer - Handle to TransformerImpl.

stylesheetTree - The compiled stylesheet tree.

methodKey - A key that uniquely identifies this class and method call.

Throws:

XSLProcessorException - thrown if something goes wrong while running the extension handler.

MalformedURLException - if loading trouble

FileNotFoundException - if loading trouble

IOException - if loading trouble

javax.xml.transform.TransformerException - if parsing trouble