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* published by the Free Software Foundation. Oracle designates this
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package javax.xml.xpath;
import org.xml.sax.InputSource;
import javax.xml.namespace.QName;
/**
* <p><code>XPathExpression</code> provides access to compiled XPath expressions.</p>
*
* <a name="XPathExpression-evaluation"/>
* <table 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>
*
* <p>An XPath expression is not thread-safe and not reentrant.
* In other words, it is the application's responsibility to make
* sure that one {@link XPathExpression} object is not used from
* more than one thread at any given time, and while the <code>evaluate</code>
* method is invoked, applications may not recursively call
* the <code>evaluate</code> method.
* <p>
*
* @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
* @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
* @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 {
/**
* <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 (a node, 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;
/**
* <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 (a node, 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;
/**
* <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;
/**
* <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;
}