001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.jxpath;
018    
019    import java.io.Serializable;
020    
021    /**
022     * Variables provide access to a global set of values accessible via XPath.
023     * XPath can reference variables using the <code>"$varname"</code> syntax.
024     * To use a custom implementation of this interface, pass it to
025     * {@link JXPathContext#setVariables JXPathContext.setVariables()}
026     *
027     * @author Dmitri Plotnikov
028     * @version $Revision: 652925 $ $Date: 2008-05-02 17:05:41 -0500 (Fri, 02 May 2008) $
029     */
030    public interface Variables extends Serializable {
031    
032        /**
033         * Returns true if the specified variable is declared.
034         * @param varName variable name
035         * @return boolean
036         */
037        boolean isDeclaredVariable(String varName);
038    
039        /**
040         * Returns the value of the specified variable.
041         * @param varName variable name
042         * @return Object value
043         * @throws IllegalArgumentException if there is no such variable.
044         */
045        Object getVariable(String varName);
046    
047        /**
048         * Defines a new variable with the specified value or modifies
049         * the value of an existing variable.
050         * May throw UnsupportedOperationException.
051         * @param varName variable name
052         * @param value to declare
053         */
054        void declareVariable(String varName, Object value);
055    
056        /**
057         * Removes an existing variable. May throw UnsupportedOperationException.
058         *
059         * @param varName is a variable name without the "$" sign
060         */
061        void undeclareVariable(String varName);
062    }