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     *
022     *  @since 1.0
023     *  @version $Id: JexlContext.java 885553 2009-11-30 19:28:40Z henrib $
024     */
025    public interface JexlContext {
026        /**
027         * Gets the value of a variable.
028         * @param name the variable's name
029         * @return the value
030         */
031        Object get(String name);
032    
033        /**
034         * Sets the value of a variable.
035         * @param name the variable's name
036         * @param value the variable's value
037         */
038        void set(String name, Object value);
039    
040        /**
041         * Checks whether a variable is defined in this context.
042         * <p>A variable may be defined with a null value; this method checks whether the
043         * value is null or if the variable is undefined.</p>
044         * @param name the variable's name
045         * @return true if it exists, false otherwise
046         */
047        boolean has(String name);
048    }