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 */
017package 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 */
026public 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}