package org.orbeon.jaxen;
/*
$Id: XPath.java,v 1.11 2006/02/05 21:47:41 elharo Exp $
Copyright 2003 The Werken Company. All Rights Reserved.
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* Redistributions of source code must retain the above copyright
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* Redistributions in binary form must reproduce the above copyright
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* Neither the name of the Jaxen Project nor the names of its
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TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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*/
import java.util.List;
/** Defines the interface to an object which represents an XPath 1.0 expression which
* can be evaluated against a variety of different XML object models.
*
* <p>
* Most of the evaluation methods take a context object. This is typically a
* node or node-set object (which is typically a <code>List</code>
* of node objects) or a Jaxen <code>Context</code> object.
* A null context is allowed, meaning that
* there are no XML nodes on which to evaluate.
* </p>
*
* @see org.orbeon.jaxen.dom4j.Dom4jXPath XPath for dom4j
* @see org.orbeon.jaxen.jdom.JDOMXPath XPath for JDOM
* @see org.orbeon.jaxen.dom.DOMXPath XPath for W3C DOM
*
* @author <a href="mailto:bob@eng.werken.com">bob mcwhirter</a>
* @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
*/
public interface XPath
{
// ----------------------------------------------------------------------
// Basic Evaluation
// ----------------------------------------------------------------------
/** Evaluate this XPath against the given context.
*
* <p>
* The context of evaluation my be a <em>document</em>,
* an <em>element</em>, or a set of <em>elements</em>.
* </p>
*
* <p>
* If the expression evaluates to an XPath string, number, or boolean
* type, then the equivalent Java object type is returned.
* Otherwise, if the result is a node-set, then the returned value is a
* <code>List</code>.
* </p>
*
* <p>
* When using this method, one must be careful to
* test the class of the returned objects, and of
* each of the composite members if a <code>List</code>
* is returned. If the returned members are XML nodes,
* they will be the actual <code>Document</code>,
* <code>Element</code> or <code>Attribute</code> objects
* as defined by the concrete XML object-model implementation,
* directly from the context document. This method <strong>does not
* return <em>copies</em> of anything</strong>. It merely returns
* references to nodes within the source document.
* </p>
*
* @param context the node, node-set or Context object for evaluation.
* This value can be null.
*
* @return the result of evaluating the XPath expression
* against the supplied context
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
Object evaluate(Object context) throws JaxenException;
// ----------------------------------------------------------------------
// Advanced Evaluation
// ----------------------------------------------------------------------
/** Retrieve a string-value interpretation of this XPath
* expression when evaluated against the given context.
*
* <p>
* The string-value of the expression is determined per
* the <code>string(..)</code> core function as defined
* in the XPath specification. This means that an expression
* that selects more than one nodes will return the string value
* of the first node in the node set..
* </p>
*
* @deprecated use {@link #stringValueOf(Object)} instead
*
* @param context the node, node-set or Context object for evaluation.
* This value can be null.
*
* @return the string-value of this expression
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
String valueOf(Object context)
throws JaxenException;
/** Retrieve a string-value interpretation of this XPath
* expression when evaluated against the given context.
*
* <p>
* The string-value of the expression is determined per
* the <code>string(..)</code> core function as defined
* in the XPath specification. This means that an expression
* that selects more than one nodes will return the string value
* of the first node in the node set..
* </p>
*
* @param context the node, node-set or Context object for evaluation.
* This value can be null
*
* @return the string-value interpretation of this expression
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
String stringValueOf(Object context)
throws JaxenException;
/** Retrieve the boolean value of the first node in document order
* returned by this XPath expression when evaluated in
* the given context.
*
* <p>
* The boolean-value of the expression is determined per
* the <code>boolean()</code> function defined
* in the XPath specification. This means that an expression
* that selects zero nodes will return <code>false</code>,
* while an expression that selects one or more nodes will
* return <code>true</code>. An expression that returns a string
* returns false for empty strings and true for all other strings.
* An expression that returns a number
* returns false for zero and true for non-zero numbers.
* </p>
*
* @param context the node, node-set or Context object for evaluation. This value can be null.
*
* @return the boolean-value of this expression
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
boolean booleanValueOf(Object context)
throws JaxenException;
/** Retrieve the number-value of the first node in document order
* returned by this XPath expression when evaluated in
* the given context.
*
* <p>
* The number-value of the expression is determined per
* the <code>number(..)</code> core function as defined
* in the XPath specification. This means that if this
* expression selects multiple nodes, the number-value
* of the first node is returned.
* </p>
*
* @param context the node, node-set or Context object for evaluation. This value can be null.
*
* @return the number-value interpretation of this expression
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
Number numberValueOf(Object context)
throws JaxenException;
// ----------------------------------------------------------------------
// Selection
// ----------------------------------------------------------------------
/** Select all nodes that are selectable by this XPath
* expression. If multiple nodes match, multiple nodes
* will be returned.
*
* <p>
* <b>NOTE:</b> In most cases, nodes will be returned
* in document-order, as defined by the XML Canonicalization
* specification. The exception occurs when using XPath
* expressions involving the <code>union</code> operator
* (denoted with the pipe '|' character).
* </p>
*
* @see #selectSingleNode
*
* @param context the node, node-set or Context object for evaluation.
* This value can be null.
*
* @return the node-set of all items selected
* by this XPath expression.
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
List selectNodes(Object context)
throws JaxenException;
/**
* <p>
* Return the first node in document order that is selected by this
* XPath expression.
* </p>
*
* @see #selectNodes
*
* @param context the node, node-set or Context object for evaluation.
* This value can be null.
*
* @return the first node in document order selected by this XPath expression
*
* @throws JaxenException if an error occurs while attempting
* to evaluate the expression
*/
Object selectSingleNode(Object context)
throws JaxenException;
// ----------------------------------------------------------------------
// Helpers
// ----------------------------------------------------------------------
/** Add a namespace prefix-to-URI mapping for this XPath
* expression.
*
* <p>
* Namespace prefix-to-URI mappings in an XPath are independent
* of those used within any document. Only the mapping explicitly
* added to this XPath will be available for resolving the
* XPath expression.
* </p>
*
* <p>
* This is a convenience method for adding mappings to the
* default {@link NamespaceContext} in place for this XPath.
* If you have installed a specific custom <code>NamespaceContext</code>,
* then this method will throw a <code>JaxenException</code>.
* </p>
*
* @param prefix the namespace prefix
* @param uri the namespace URI
*
* @throws JaxenException if a <code>NamespaceContext</code>
* used by this XPath has been explicitly installed
*/
void addNamespace(String prefix,
String uri)
throws JaxenException;
// ----------------------------------------------------------------------
// Properties
// ----------------------------------------------------------------------
/** Set a <code>NamespaceContext</code> for this
* XPath expression.
*
* <p>
* A <code>NamespaceContext</code> is responsible for translating
* namespace prefixes within the expression into namespace URIs.
* </p>
*
* @see NamespaceContext
* @see NamespaceContext#translateNamespacePrefixToUri
*
* @param namespaceContext the <code>NamespaceContext</code> to
* install for this expression
*/
void setNamespaceContext(NamespaceContext namespaceContext);
/** Set a <code>FunctionContext</code> for this XPath
* expression.
*
* <p>
* A <code>FunctionContext</code> is responsible for resolving
* all function calls used within the expression.
* </p>
*
* @see FunctionContext
* @see FunctionContext#getFunction
*
* @param functionContext the <code>FunctionContext</code> to
* install for this expression
*/
void setFunctionContext(FunctionContext functionContext);
/** Set a <code>VariableContext</code> for this XPath
* expression.
*
* <p>
* A <code>VariableContext</code> is responsible for resolving
* all variables referenced within the expression.
* </p>
*
* @see VariableContext
* @see VariableContext#getVariableValue
*
* @param variableContext the <code>VariableContext</code> to
* install for this expression.
*/
void setVariableContext(VariableContext variableContext);
/** Retrieve the <code>NamespaceContext</code> used by this XPath
* expression.
*
* <p>
* A <code>FunctionContext</code> is responsible for resolving
* all function calls used within the expression.
* </p>
*
* <p>
* If this XPath expression has not previously had a <code>NamespaceContext</code>
* installed, a new default <code>NamespaceContext</code> will be created,
* installed and returned.
* </p>
*
* @see NamespaceContext
*
* @return the <code>NamespaceContext</code> used by this expression
*/
NamespaceContext getNamespaceContext();
/** Retrieve the <code>FunctionContext</code> used by this XPath
* expression.
*
* <p>
* A <code>FunctionContext</code> is responsible for resolving
* all function calls used within the expression.
* </p>
*
* <p>
* If this XPath expression has not previously had a <code>FunctionContext</code>
* installed, a new default <code>FunctionContext</code> will be created,
* installed and returned.
* </p>
*
* @see FunctionContext
*
* @return the <code>FunctionContext</code> used by this expression
*/
FunctionContext getFunctionContext();
/** Retrieve the <code>VariableContext</code> used by this XPath
* expression.
*
* <p>
* A <code>VariableContext</code> is responsible for resolving
* all variables referenced within the expression.
* </p>
*
* <p>
* If this XPath expression has not previously had a <code>VariableContext</code>
* installed, a new default <code>VariableContext</code> will be created,
* installed and returned.
* </p>
*
* @see VariableContext
*
* @return the <code>VariableContext</code> used by this expression
*/
VariableContext getVariableContext();
/** Retrieve the XML object-model-specific {@link Navigator}
* used to evaluate this XPath expression.
*
* @return the implementation-specific <code>Navigator</code>
*/
Navigator getNavigator();
}