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    1   /*
    2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/VariableContext.java,v 1.9 2005/09/25 11:40:36 elharo Exp $
    3    * $Revision: 1.9 $
    4    * $Date: 2005/09/25 11:40:36 $
    5    *
    6    * ====================================================================
    7    *
    8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
    9    * All rights reserved.
    10   *
    11   * Redistribution and use in source and binary forms, with or without
    12   * modification, are permitted provided that the following conditions
    13   * are met:
    14   *
    15   * 1. Redistributions of source code must retain the above copyright
    16   *    notice, this list of conditions, and the following disclaimer.
    17   *
    18   * 2. Redistributions in binary form must reproduce the above copyright
    19   *    notice, this list of conditions, and the disclaimer that follows
    20   *    these conditions in the documentation and/or other materials
    21   *    provided with the distribution.
    22   *
    23   * 3. The name "Jaxen" must not be used to endorse or promote products
    24   *    derived from this software without prior written permission.  For
    25   *    written permission, please contact license@jaxen.org.
    26   *
    27   * 4. Products derived from this software may not be called "Jaxen", nor
    28   *    may "Jaxen" appear in their name, without prior written permission
    29   *    from the Jaxen Project Management (pm@jaxen.org).
    30   *
    31   * In addition, we request (but do not require) that you include in the
    32   * end-user documentation provided with the redistribution and/or in the
    33   * software itself an acknowledgement equivalent to the following:
    34   *     "This product includes software developed by the
    35   *      Jaxen Project <http://www.jaxen.org/>."
    36   * Alternatively, the acknowledgment may be graphical using the logos
    37   * available at http://www.jaxen.org/
    38   *
    39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
    43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    50   * SUCH DAMAGE.
    51   *
    52   * ====================================================================
    53   * This software consists of voluntary contributions made by many
    54   * individuals on behalf of the Jaxen Project and was originally
    55   * created by bob mcwhirter <bob@werken.com> and
    56   * James Strachan <jstrachan@apache.org>.  For more information on the
    57   * Jaxen Project, please see <http://www.jaxen.org/>.
    58   *
    59   * $Id: VariableContext.java,v 1.9 2005/09/25 11:40:36 elharo Exp $
    60   */
    61
    62
    63  package org.jaxen;
    64
    65  /*** Resolves variable bindings within an XPath expression.
    66   *
    67   *  <p>
    68   *  Variables within an XPath expression are denoted using
    69   *  notation such as <code>$varName</code> or
    70   *  <code>$nsPrefix:varName</code>, and may
    71   *  refer to a <code>Boolean</code>, <code>Double</code>, <code>String</code>,
    72   *  node-set (<code>List</code>) or individual XML node.
    73   *  </p>
    74   *
    75   *  <p>
    76   *  When a variable is bound to a node-set, the
    77   *  actual Java object returned should be a <code>java.util.List</code>
    78   *  containing XML nodes from the object-model (e.g. dom4j, JDOM, DOM, etc.)
    79   *  being used with the XPath.
    80   *  </p>
    81   *
    82   *  <p>
    83   *  A variable may validly be assigned the <code>null</code> value,
    84   *  but an unbound variable (one that this context does not know about)
    85   *  should cause an {@link UnresolvableException} to be thrown.
    86   *  </p>
    87   *
    88   *  @see SimpleVariableContext
    89   *  @see NamespaceContext
    90   *
    91   *  @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
    92   *  @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
    93   */
    94  public interface VariableContext
    95  {
    96      /*** An implementation should return the value of an XPath variable
    97       *  based on the namespace URI and local name of the variable-reference
    98       *  expression.
    99       *
    100      *  <p>
    101      *  It must not use the prefix parameter to select a variable,
    102      *  because a prefix could be bound to any namespace; the prefix parameter
    103      *  could be used in debugging output or other generated information.
    104      *  The prefix may otherwise be ignored.
    105      *  </p>
    106      *
    107      *  @param namespaceURI  the namespace URI to which the prefix parameter
    108      *                       is bound in the XPath expression. If the variable
    109      *                       reference expression had no prefix, the namespace
    110      *                       URI is <code>null</code>.
    111      *  @param prefix        the prefix that was used in the variable reference
    112      *                       expression; this value is ignored and has no effect
    113      *  @param localName     the local name of the variable-reference
    114      *                       expression. If there is no prefix, then this is
    115      *                       the whole name of the variable.
    116      *
    117      *  @return  the variable's value (which can be <code>null</code>)
    118      *  @throws UnresolvableException  when the variable cannot be resolved
    119      */
    120     public Object getVariableValue( String namespaceURI,
    121                                     String prefix,
    122                                     String localName )
    123         throws UnresolvableException;
    124 }