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.jexl2;
018    
019    /**
020     * Manages variables which can be referenced in a JEXL expression.
021     * <p>Note that JEXL may use '$jexl' and '$ujexl' variables for internal purpose; setting or getting those
022     * variables may lead to unexpected results unless specified otherwise.</p>
023     *  @since 1.0
024     *  @version $Id: JexlContext.java 1202769 2011-11-16 16:33:02Z henrib $
025     */
026    public interface JexlContext {
027        /**
028         * Gets the value of a variable.
029         * @param name the variable's name
030         * @return the value
031         */
032        Object get(String name);
033    
034        /**
035         * Sets the value of a variable.
036         * @param name the variable's name
037         * @param value the variable's value
038         */
039        void set(String name, Object value);
040    
041        /**
042         * Checks whether a variable is defined in this context.
043         * <p>A variable may be defined with a null value; this method checks whether the
044         * value is null or if the variable is undefined.</p>
045         * @param name the variable's name
046         * @return true if it exists, false otherwise
047         */
048        boolean has(String name);
049    }