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// $Id: XPathExpression.java 446598 2006-09-15 12:55:40Z jeremias $

package javax.xml.xpath;

import org.xml.sax.InputSource;
import javax.xml.namespace.QName;


XPathExpression provides access to compiled XPath expressions.



  
    

      Evaluation of XPath Expressions.
    

  
  
    

      context
      
        If a request is made to evaluate the expression in the absence
of a context item, an empty document node will be used for the context.
For the purposes of evaluating XPath expressions, a DocumentFragment
is treated like a Document node.
     
   

   

     variables
      If the expression contains a variable reference, its value will be found through the XPathVariableResolver. An XPathExpressionException is raised if the variable resolver is undefined or the resolver returns null for the variable.
       The value of a variable must be immutable through the course of any single evaluation.

     		
   

   

     functions
      If the expression contains a function reference, the function will be found through the XPathFunctionResolver. An XPathExpressionException is raised if the function resolver is undefined or the function resolver returns null for the function.

     		
   

   

     QNames
     
       QNames in the expression are resolved against the XPath namespace context.
     
   

   

     result
      This result of evaluating an expression is converted to an instance of the desired return type. Valid return types are defined in XPathConstants. Conversion to the return type follows XPath conversion rules.

     		
   




Author: Norman Walsh,  Jeff Suttor
See Also:
Version:$Revision: 446598 $, $Date: 2006-09-15 08:55:40 -0400 (Fri, 15 Sep 2006) $
Since:1.5
/**
 * <p><code>XPathExpression</code> provides access to compiled XPath expressions.</p>
 *
 * <table id="XPathExpression-evaluation" border="1" cellpadding="2">
 *   <thead>
 *     <tr>
 *       <th colspan="2">Evaluation of XPath Expressions.</th>
 *     </tr>
 *   </thead>
 *   <tbody>
 *     <tr>
 *       <td>context</td>
 *       <td>
 *         If a request is made to evaluate the expression in the absence
 * of a context item, an empty document node will be used for the context.
 * For the purposes of evaluating XPath expressions, a DocumentFragment
 * is treated like a Document node.
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>variables</td>
 *      <td>
 *        If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}.
 *        An {@link XPathExpressionException} is raised if the variable resolver is undefined or
 *        the resolver returns <code>null</code> for the variable.
 *        The value of a variable must be immutable through the course of any single evaluation.</p>
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>functions</td>
 *      <td>
 *        If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}.
 *        An {@link XPathExpressionException} is raised if the function resolver is undefined or
 *        the function resolver returns <code>null</code> for the function.</p>
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>QNames</td>
 *      <td>
 *        QNames in the expression are resolved against the XPath namespace context.
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>result</td>
 *      <td>
 *        This result of evaluating an expression is converted to an instance of the desired return type.
 *        Valid return types are defined in {@link XPathConstants}.
 *        Conversion to the return type follows XPath conversion rules.</p>
 *      </td>
 *    </tr>
 * </table>
 *
 * @author  <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
 * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @version $Revision: 446598 $, $Date: 2006-09-15 08:55:40 -0400 (Fri, 15 Sep 2006) $
 * @see <a href="http://www.w3.org/TR/xpath#section-Expressions">XML Path Language (XPath) Version 1.0, Expressions</a>
 * @since 1.5
 */
public interface XPathExpression {
    
    
Evaluate the compiled XPath expression in the specified context and return the result as the specified type.


See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.


If returnType is not one of the types defined in XPathConstants, then an IllegalArgumentException is thrown.


If a null value is provided for 
item, an empty document will be used for the
context.
If returnType is null, then a NullPointerException is thrown.
 

Params:
  • item – The starting context (node or node list, for example).
  • returnType – The desired return type.
Throws:
Returns:The Object that is the result of evaluating the expression and converting the result to
  returnType.
/**
     * <p>Evaluate the compiled XPath expression in the specified context and return the result as the specified type.</p>
     *
     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     * 
     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
     * then an <code>IllegalArgumentException</code> is thrown.</p>
     * 
     * <p>If a <code>null</code> value is provided for 
     * <code>item</code>, an empty document will be used for the
     * context.
     * If <code>returnType</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p> 
     *
     * @param item The starting context (node or node list, for example).
     * @param returnType The desired return type.
     * 
     * @return The <code>Object</code> that is the result of evaluating the expression and converting the result to
     *   <code>returnType</code>.
     * 
     * @throws XPathExpressionException If the expression cannot be evaluated.
     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
     * @throws NullPointerException If  <code>returnType</code> is <code>null</code>. 
     */
    public Object evaluate(Object item, QName returnType)
        throws XPathExpressionException;

    
Evaluate the compiled XPath expression in the specified context and return the result as a String.


This method calls evaluate(Object item, QName returnType) with a returnType of XPathConstants.STRING.


See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.


If a null value is provided for 
item, an empty document will be used for the
context.

Params:
  • item – The starting context (node or node list, for example).
Throws:
Returns:The String that is the result of evaluating the expression and converting the result to a 
  String.
/**
     * <p>Evaluate the compiled XPath expression in the specified context and return the result as a <code>String</code>.</p>
     *
     * <p>This method calls {@link #evaluate(Object item, QName returnType)} with a <code>returnType</code> of
     * {@link XPathConstants#STRING}.</p>
     * 
     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     * 
     * <p>If a <code>null</code> value is provided for 
     * <code>item</code>, an empty document will be used for the
     * context.
     *
     * @param item The starting context (node or node list, for example).
     * 
     * @return The <code>String</code> that is the result of evaluating the expression and converting the result to a 
     *   <code>String</code>.
     * 
     * @throws XPathExpressionException If the expression cannot be evaluated.
     */
    public String evaluate(Object item)
        throws XPathExpressionException;

    
Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as the
specified type.


This method builds a data model for the InputSource and calls evaluate(Object item, QName returnType) on the resulting document object.


See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.


If returnType is not one of the types defined in XPathConstants, then an IllegalArgumentException is thrown.


If source or returnType is null,
then a NullPointerException is thrown.
 

Params:
  • source – The InputSource of the document to evaluate over.
  • returnType – The desired return type.
Throws:
Returns:The Object that is the result of evaluating the expression and converting the result to
  returnType.
/**
     * <p>Evaluate the compiled XPath expression in the context of the specified <code>InputSource</code> and return the result as the
     * specified type.</p>
     *
     * <p>This method builds a data model for the {@link InputSource} and calls
     * {@link #evaluate(Object item, QName returnType)} on the resulting document object.</p>
     * 
     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     * 
     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
     * then an <code>IllegalArgumentException</code> is thrown.</p>
     * 
     * <p>If <code>source</code> or <code>returnType</code> is <code>null</code>,
     * then a <code>NullPointerException</code> is thrown.</p> 
     *
     * @param source The <code>InputSource</code> of the document to evaluate over.
     * @param returnType The desired return type.
     * 
     * @return The <code>Object</code> that is the result of evaluating the expression and converting the result to
     *   <code>returnType</code>.
     * 
     * @throws XPathExpressionException If the expression cannot be evaluated.
     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
     * @throws NullPointerException If  <code>source</code> or <code>returnType</code> is <code>null</code>. 
     */
    public Object evaluate(InputSource source, QName returnType)
        throws XPathExpressionException;
    
    
Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as a
String.


This method calls evaluate(InputSource source, QName returnType) with a returnType of XPathConstants.STRING.


See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.


If source is null, then a NullPointerException is thrown.
 

Params:
  • source – The InputSource of the document to evaluate over.
Throws:
Returns:The String that is the result of evaluating the expression and converting the result to a 
  String.
/**
     * <p>Evaluate the compiled XPath expression in the context of the specified <code>InputSource</code> and return the result as a
     * <code>String</code>.</p>
     *
     * <p>This method calls {@link #evaluate(InputSource source, QName returnType)} with a <code>returnType</code> of
     * {@link XPathConstants#STRING}.</p>
     * 
     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     * 
     * <p>If <code>source</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p> 
     *
     * @param source The <code>InputSource</code> of the document to evaluate over.
     * 
     * @return The <code>String</code> that is the result of evaluating the expression and converting the result to a 
     *   <code>String</code>.
     * 
     * @throws XPathExpressionException If the expression cannot be evaluated.
     * @throws NullPointerException If  <code>source</code> is <code>null</code>. 
     */
    public String evaluate(InputSource source)
        throws XPathExpressionException;
}