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 }