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/*
* $Id: XPath.java,v 1.8 2010-11-01 04:36:13 joehw Exp $
* %W% %E%
*/
package mf.javax.xml.xpath;
import org.xml.sax.InputSource;
import mf.javax.xml.namespace.QName;
import mf.javax.xml.namespace.NamespaceContext;
/**
* <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
*
* <a name="XPath-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}
* 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>
*
* <p>An XPath object is not thread-safe and not reentrant.
* In other words, it is the application's responsibility to make
* sure that one {@link XPath} 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="Norman.Walsh@Sun.com">Norman Walsh</a>
* @author <a href="Jeff.Suttor@Sun.com">Jeff Suttor</a>
* @version $Revision: 1.8 $, $Date: 2010-11-01 04:36:13 $
* @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>
* @since 1.5
*/
public interface XPath {
/**
* <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();
/**
* <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);
/**
* <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();
/**
* <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);
/**
* <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();
/**
* <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);
/**
* <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();
/**
* <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 resovled with the <code>XPathFunctionResolver</code>.</p>
*
* <p>If <code>expression</code> contains any variables, the
* {@link XPathVariableResolver} in effect
* <strong>at compile time</strong> will be used to resolve them.</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;
/**
* <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 (a node, 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;
/**
* <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 (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 <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;
/**
* <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;
/**
* <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;
}