http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
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 * The ASF licenses this file to You under the Apache License, Version 2.0
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 * distributed under the License is distributed on an "AS IS" BASIS,
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// $Id: XPath.java 569998 2007-08-27 04:40:02Z mrglavas $

package javax.xml.xpath;

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


XPath provides access to the XPath evaluation environment and 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 set with setXPathVariableResolver(XPathVariableResolver resolver). 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 set with setXPathFunctionResolver(XPathFunctionResolver resolver). 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 set with setNamespaceContext(NamespaceContext nsContext). 
   

   

     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: 569998 $, $Date: 2007-08-27 00:40:02 -0400 (Mon, 27 Aug 2007) $
Since:1.5
/**
 * <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
 *
 * <table id="XPath-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}
 *        set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}.
 *        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}
 *        set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}.
 *        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
 *        set with {@link #setNamespaceContext(NamespaceContext nsContext)}.
 *      </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="Norman.Walsh@Sun.com">Norman Walsh</a>
 * @author  <a href="Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @version $Revision: 569998 $, $Date: 2007-08-27 00:40:02 -0400 (Mon, 27 Aug 2007) $
 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>
 * @since 1.5
 */
public interface XPath {
    
	
Reset this XPath to its original configuration.


XPath is reset to the same state as when it was created with XPathFactory.newXPath(). reset() is designed to allow the reuse of existing XPaths
thus saving resources associated with the creation of new XPaths.


The reset XPath is not guaranteed to have the same XPathFunctionResolver, XPathVariableResolver or NamespaceContext Objects, e.g. Object.equals(Object obj). It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver
and NamespaceContext.


/**
	 * <p>Reset this <code>XPath</code> to its original configuration.</p>
	 * 
	 * <p><code>XPath</code> is reset to the same state as when it was created with
	 * {@link XPathFactory#newXPath()}.
	 * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s
	 * thus saving resources associated with the creation of new <code>XPath</code>s.</p>
	 * 
	 * <p>The reset <code>XPath</code> is not guaranteed to have the same {@link XPathFunctionResolver}, {@link XPathVariableResolver}
	 * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.
	 * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>, <code>XPathVariableResolver</code>
	 * and <code>NamespaceContext</code>.</p>
	 */
	public void reset();

    
Establish a variable resolver.


A NullPointerException is thrown if resolver is null.


Params:
  • resolver – Variable resolver.
 @throws NullPointerException If resolver is null.
/**
     * <p>Establish a variable resolver.</p>
     * 
     * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
     * 
     * @param resolver Variable resolver.
     * 
     *  @throws NullPointerException If <code>resolver</code> is <code>null</code>.
     */
    public void setXPathVariableResolver(XPathVariableResolver resolver);

    
Return the current variable resolver.


null is returned in no variable resolver is in effect.

 

Returns:Current variable resolver.
/**
       * <p>Return the current variable resolver.</p>
       * 
       * <p><code>null</code> is returned in no variable resolver is in effect.</p>
       *  
       * @return Current variable resolver.
       */
    public XPathVariableResolver getXPathVariableResolver();

    
Establish a function resolver.


A NullPointerException is thrown if resolver is null.


Params:
  • resolver – XPath function resolver.
Throws:
/**
       * <p>Establish a function resolver.</p>
       * 
       * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
       * 
       * @param resolver XPath function resolver.
       * 
       * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
       */
    public void setXPathFunctionResolver(XPathFunctionResolver resolver);

    
Return the current function resolver.


null is returned in no function resolver is in effect.


Returns:Current function resolver.
/**
       * <p>Return the current function resolver.</p>
       * 
       * <p><code>null</code> is returned in no function resolver is in effect.</p>
       * 
       * @return Current function resolver.
       */
    public XPathFunctionResolver getXPathFunctionResolver();

    
Establish a namespace context.


A NullPointerException is thrown if nsContext is null.


Params:
  • nsContext – Namespace context to use.
Throws:
/**
       * <p>Establish a namespace context.</p>
       * 
       * <p>A <code>NullPointerException</code> is thrown if <code>nsContext</code> is <code>null</code>.</p>
       * 
       * @param nsContext Namespace context to use.
       * 
       * @throws NullPointerException If <code>nsContext</code> is <code>null</code>.
       */
    public void setNamespaceContext(NamespaceContext nsContext);

    
Return the current namespace context.


null is returned in no namespace context is in effect.


Returns:Current Namespace context.
/**
       * <p>Return the current namespace context.</p>
       * 
       * <p><code>null</code> is returned in no namespace context is in effect.</p>
       * 
       * @return Current Namespace context.
       */
    public NamespaceContext getNamespaceContext();

    
Compile an XPath expression for later evaluation.


If expression contains any XPathFunctions, they must be available via the XPathFunctionResolver. An XPathExpressionException will be thrown if the XPathFunction
cannot be resolved with the XPathFunctionResolver.

 

If expression is null, a NullPointerException is thrown.
 

Params:
  • expression – The XPath expression.
Throws:
Returns:Compiled XPath expression.
/** 
       * <p>Compile an XPath expression for later evaluation.</p>
       * 
       * <p>If <code>expression</code> contains any {@link XPathFunction}s,
       * they must be available via the {@link XPathFunctionResolver}.
       * An {@link XPathExpressionException} will be thrown if the <code>XPathFunction</code>
       * cannot be resolved with the <code>XPathFunctionResolver</code>.</p>
       *  
       * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is thrown.</p> 
       *
       * @param expression The XPath expression.
       * 
       * @return Compiled XPath expression.
    
       * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
       * @throws NullPointerException If <code>expression</code> is <code>null</code>.
       */
    public XPathExpression compile(String expression)
        throws XPathExpressionException;

    
Evaluate an 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 ( NUMBER, STRING, BOOLEAN, NODE or NODESET) then an IllegalArgumentException is thrown.


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


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

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


This method calls evaluate(String expression, 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.
If expression is null, then a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • 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 an XPath expression in the specified context and return the result as a <code>String</code>.</p>
     *
     * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a <code>returnType</code> of
     * {@link XPathConstants#STRING}.</p>
     * 
     * <p>See <a href="#XPath-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.
     * If <code>expression</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
     * 
     * @param expression The XPath expression.
     * @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 <code>expression</code> cannot be evaluated.
     * @throws NullPointerException If <code>expression</code> is <code>null</code>.
     */
    public String evaluate(String expression, Object item)
        throws XPathExpressionException;

    
Evaluate an 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(String expression, 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 expression, source or returnType is null,
then a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • source – The input source of the document to evaluate over.
  • returnType – The desired return type.
Throws:
Returns:The Object that encapsulates the result of evaluating the expression.
/**
     * <p>Evaluate an 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(String expression, Object item, QName returnType)} on the resulting document object.</p>
     *
     * <p>See <a href="#XPath-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>expression</code>, <code>source</code> or <code>returnType</code> is <code>null</code>,
     * then a <code>NullPointerException</code> is thrown.</p>
     * 
     * @param expression The XPath expression.
     * @param source The input source of the document to evaluate over.
     * @param returnType The desired return type.
     * 
     * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
     * 
     * @throws XPathExpressionException If expression cannot be evaluated.
     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
     * @throws NullPointerException If <code>expression</code>, <code>source</code> or <code>returnType</code>
     *   is <code>null</code>.
     */
    public Object evaluate(
        String expression,
        InputSource source,
        QName returnType)
        throws XPathExpressionException;

    
Evaluate an XPath expression in the context of the specified InputSource
and return the result as a String.


This method calls evaluate(String expression, 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 expression or source is null,
then a NullPointerException is thrown.


Params:
  • expression – The XPath expression.
  • 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 an 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(String expression, InputSource source, QName returnType)} with a
     * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
     *
     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
     * variable, function and QName resolution and return type conversion.</p>
     * 
     * <p>If <code>expression</code> or <code>source</code> is <code>null</code>,
     * then a <code>NullPointerException</code> is thrown.</p>
     * 
     * @param expression The XPath expression.
     * @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 expression cannot be evaluated.
     * @throws NullPointerException If <code>expression</code> or <code>source</code> is <code>null</code>.
     */
    public String evaluate(String expression, InputSource source)
        throws XPathExpressionException;
}