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package org.navimatrix.jaxen;

/*
 $Id: XPath.java,v 1.12 2006/06/03 20:07:37 elharo Exp $

 Copyright 2003 The Werken Company. All Rights Reserved.
 
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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.
 *
 *  

* Most of the evaluation methods take a context object. This is typically a * node or node-set object (which is typically a List * of node objects) or a Jaxen Context object. * A null context is allowed, meaning that * there are no XML nodes on which to evaluate. *

* * @see org.navimatrix.jaxen.dom4j.Dom4jXPath XPath for dom4j * @see org.navimatrix.jaxen.jdom.JDOMXPath XPath for JDOM * @see org.navimatrix.jaxen.dom.DOMXPath XPath for W3C DOM * * @author bob mcwhirter * @author James Strachan */ public interface XPath { // ---------------------------------------------------------------------- // Basic Evaluation // ---------------------------------------------------------------------- /** Evaluate this XPath against the given context. * *

* The context of evaluation my be a document, * an element, or a set of elements. *

* *

* 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 * List. *

* *

* 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 List * is returned. If the returned members are XML nodes, * they will be the actual Document, * Element or Attribute objects * as defined by the concrete XML object-model implementation, * directly from the context document. This method does not * return copies of anything. It merely returns * references to nodes within the source document. *

* * @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. * *

* The string-value of the expression is determined per * the string(..) 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.. *

* * @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. * *

* The string-value of the expression is determined per * the string(..) 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.. *

* * @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. * *

* The boolean-value of the expression is determined per * the boolean() function defined * in the XPath specification. This means that an expression * that selects zero nodes will return false, * while an expression that selects one or more nodes will * return true. 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. *

* * @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. * *

* The number-value of the expression is determined per * the number(..) 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. *

* * @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. * *

* NOTE: 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 union operator * (denoted with the pipe '|' character). *

* * @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; /** *

* Return the first node in document order that is selected by this * XPath expression. *

* * @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. * *

* 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. *

* *

* 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 NamespaceContext, * then this method will throw a JaxenException. *

* * @param prefix the namespace prefix * @param uri the namespace URI * * @throws JaxenException if a NamespaceContext * used by this XPath has been explicitly installed */ void addNamespace(String prefix, String uri) throws JaxenException; // ---------------------------------------------------------------------- // Properties // ---------------------------------------------------------------------- /** Set a NamespaceContext for this * XPath expression. * *

* A NamespaceContext is responsible for translating * namespace prefixes within the expression into namespace URIs. *

* * @see NamespaceContext * @see NamespaceContext#translateNamespacePrefixToUri * * @param namespaceContext the NamespaceContext to * install for this expression */ void setNamespaceContext(NamespaceContext namespaceContext); /** Set a FunctionContext for this XPath * expression. * *

* A FunctionContext is responsible for resolving * all function calls used within the expression. *

* * @see FunctionContext * @see FunctionContext#getFunction * * @param functionContext the FunctionContext to * install for this expression */ void setFunctionContext(FunctionContext functionContext); /** Set a VariableContext for this XPath * expression. * *

* A VariableContext is responsible for resolving * all variables referenced within the expression. *

* * @see VariableContext * @see VariableContext#getVariableValue * * @param variableContext the VariableContext to * install for this expression. */ void setVariableContext(VariableContext variableContext); /** Retrieve the NamespaceContext used by this XPath * expression. * *

* A FunctionContext is responsible for resolving * all function calls used within the expression. *

* *

* If this XPath expression has not previously had a NamespaceContext * installed, a new default NamespaceContext will be created, * installed and returned. *

* * @see NamespaceContext * * @return the NamespaceContext used by this expression */ NamespaceContext getNamespaceContext(); /** Retrieve the FunctionContext used by this XPath * expression. * *

* A FunctionContext is responsible for resolving * all function calls used within the expression. *

* *

* If this XPath expression has not previously had a FunctionContext * installed, a new default FunctionContext will be created, * installed and returned. *

* * @see FunctionContext * * @return the FunctionContext used by this expression */ FunctionContext getFunctionContext(); /** Retrieve the VariableContext used by this XPath * expression. * *

* A VariableContext is responsible for resolving * all variables referenced within the expression. *

* *

* If this XPath expression has not previously had a VariableContext * installed, a new default VariableContext will be created, * installed and returned. *

* * @see VariableContext * * @return the VariableContext used by this expression */ VariableContext getVariableContext(); /** Retrieve the XML object-model-specific {@link Navigator} * used to evaluate this XPath expression. * * @return the implementation-specific Navigator */ Navigator getNavigator(); }




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