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 java.lang.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)
  Usage:
    **For internal use only**

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract java.lang.Object` | `callFunction(FuncExtFunction extFunction, java.util.Vector args, ExpressionContext exprContext)` Process a call to a function.
    `abstract java.lang.Object` | `callFunction(java.lang.String funcName, java.util.Vector args, java.lang.Object methodKey, ExpressionContext exprContext)` Process a call to a function.
    `abstract boolean` | `isElementAvailable(java.lang.String element)` Tests whether a certain element name is known within this namespace.
    `abstract boolean` | `isFunctionAvailable(java.lang.String function)` Tests whether a certain function name is known within this namespace.
    `abstract void` | `processElement(java.lang.String localPart, ElemTemplateElement element, TransformerImpl transformer, Stylesheet stylesheetTree, java.lang.Object methodKey)` Process a call to this extension namespace via an element.

    - ### Methods inherited from class java.lang.Object

      `equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### isFunctionAvailable

          public abstract boolean isFunctionAvailable(java.lang.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(java.lang.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 java.lang.Object callFunction(java.lang.String funcName,
                                      java.util.Vector args,
                                      java.lang.Object methodKey,
                                      ExpressionContext exprContext)
                                                 throws 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:
        `TransformerException` - if parsing trouble

    - #### callFunction

          public abstract java.lang.Object callFunction(FuncExtFunction extFunction,
                                      java.util.Vector args,
                                      ExpressionContext exprContext)
                                                 throws TransformerException

      Process a call to a function.
      Parameters:
        `extFunction` - The XPath extension function.
        `args` - The arguments of the function call.
        `exprContext` - The context in which this expression is being executed.
      Returns:
        the return value of the function evaluation.
      Throws:
        `TransformerException` - if parsing trouble

    - #### processElement

          public abstract void processElement(java.lang.String localPart,
                            ElemTemplateElement element,
                            TransformerImpl transformer,
                            Stylesheet stylesheetTree,
                            java.lang.Object methodKey)
                                       throws TransformerException,
                                              java.io.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
        `java.io.IOException` - if loading trouble
        `TransformerException` - if parsing trouble

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