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1   /*
2    * Copyright 1999-2004 The Apache Software Foundation
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.jxpath;
17  
18  /***
19   * Variables provide access to a global set of values accessible via XPath.
20   * XPath can reference variables using the <code>"$varname"</code> syntax.
21   * To use a custom implementation of this interface, pass it to
22   * {@link JXPathContext#setVariables JXPathContext.setVariables()}
23   *
24   * @author Dmitri Plotnikov
25   * @version $Revision: 1.6 $ $Date: 2004/02/29 14:17:42 $
26   */
27  public interface Variables {
28  
29      /***
30       * Returns true if the specified variable is declared.
31       */
32      boolean isDeclaredVariable(String varName);
33  
34      /***
35       * Returns the value of the specified variable.
36       * Throws IllegalArgumentException if there is no such variable.
37       */
38      Object getVariable(String varName);
39  
40      /***
41       * Defines a new variable with the specified value or modifies
42       * the value of an existing variable.
43       * May throw UnsupportedOperationException.
44       */
45      void declareVariable(String varName, Object value);
46  
47      /***
48       * Removes an existing variable. May throw UnsupportedOperationException.
49       *
50       * @param varName is a variable name without the "$" sign
51       */
52      void undeclareVariable(String varName);
53  }