org.apache.xalan.extensions
Class ExtensionHandlerJavaClass

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

public class ExtensionHandlerJavaClass

extends ExtensionHandlerJava

Represents an extension namespace for XPath that handles java classes. It is recommended that the class URI be of the form:

   xalan://fully.qualified.class.name
 

However, we do not enforce this. If the class name contains a a /, we only use the part to the right of the rightmost slash. In addition, we ignore any "class:" prefix. Provides functions to test a function's existence and call a function. Also provides functions to test an element's existence and call an element.

Author:

Gary L Peskin

Field Summary

private Class	m_classObj
private Object	m_defaultInstance Provides a default Instance for use by elements that need to call an instance method.

Fields inherited from class org.apache.xalan.extensions.ExtensionHandlerJava

m_className

Fields inherited from class org.apache.xalan.extensions.ExtensionHandler

m_namespaceUri, m_scriptLang

Constructor Summary

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

Method Summary

Object	callFunction(String funcName, Vector args, Object methodKey, ExpressionContext exprContext) Process a call to a function in the java class represented by this ExtensionHandlerJavaClass.
boolean	isElementAvailable(String element) Tests whether a certain element name is known within this namespace.
boolean	isFunctionAvailable(String function) Tests whether a certain function name is known within this namespace.
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 org.apache.xalan.extensions.ExtensionHandlerJava

getFromCache, putToCache

Methods inherited from class org.apache.xalan.extensions.ExtensionHandler

getClassForName

Methods inherited from class java.lang.Object

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

Field Detail

m_classObj

private Class m_classObj

m_defaultInstance

private Object m_defaultInstance

Provides a default Instance for use by elements that need to call an instance method.

Constructor Detail

ExtensionHandlerJavaClass

public ExtensionHandlerJavaClass(String namespaceUri,
                                 String scriptLang,
                                 String className)

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

className - the fully qualified class name of the class

Method Detail

isFunctionAvailable

public boolean isFunctionAvailable(String function)

Tests whether a certain function name is known within this namespace. Simply looks for a method with the appropriate name. There is no information regarding the arguments to the function call or whether the method implementing the function is a static method or an instance method.

Specified by:

isFunctionAvailable in class ExtensionHandler

Parameters:

function - name of the function being tested

Returns:

true if its known, false if not.

isElementAvailable

public boolean isElementAvailable(String element)

Tests whether a certain element name is known within this namespace. Looks for a method with the appropriate name and signature. This method examines both static and instance methods.

Specified by:

isElementAvailable in class ExtensionHandler

Parameters:

element - name of the element being tested

Returns:

true if its known, false if not.

callFunction

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

Process a call to a function in the java class represented by this ExtensionHandlerJavaClass. There are three possible types of calls:

   Constructor:
     classns:new(arg1, arg2, ...)

   Static method:
     classns:method(arg1, arg2, ...)

   Instance method:
     classns:method(obj, arg1, arg2, ...)
 

We use the following rules to determine the type of call made:

1. If the function name is "new", call the best constructor for class represented by the namespace URI
2. If the first argument to the function is of the class specified in the namespace or is a subclass of that class, look for the best method of the class specified in the namespace with the specified arguments. Compare all static and instance methods with the correct method name. For static methods, use all arguments in the compare. For instance methods, use all arguments after the first.
3. Otherwise, select the best static or instance method matching all of the arguments. If the best method is an instance method, call the function using a default object, creating it if needed.

Specified by:

callFunction in class ExtensionHandler

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

processElement

public 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. We invoke the static or instance method in the class represented by by the namespace URI. If we don't already have an instance of this class, we create one upon the first call.

Specified by:

processElement in class ExtensionHandler

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 element call.

Throws:

IOException - if loading trouble

javax.xml.transform.TransformerException - if parsing trouble