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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  }