    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    }