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
018package org.apache.commons.jxpath;
019
020import java.io.Serializable;
021
022/**
023 * Variables provide access to a global set of values accessible via XPath. XPath can reference variables using the {@code "$varname"} syntax. To use a custom
024 * implementation of this interface, pass it to {@link JXPathContext#setVariables JXPathContext.setVariables()}
025 */
026public interface Variables extends Serializable {
027
028    /**
029     * Defines a new variable with the specified value or modifies the value of an existing variable. May throw UnsupportedOperationException.
030     *
031     * @param name variable name
032     * @param value   to declare
033     */
034    void declareVariable(String name, Object value);
035
036    /**
037     * Returns the value of the specified variable.
038     *
039     * @param name variable name
040     * @return Object value
041     * @throws IllegalArgumentException if there is no such variable.
042     */
043    Object getVariable(String name);
044
045    /**
046     * Returns true if the specified variable is declared.
047     *
048     * @param name variable name
049     * @return boolean
050     */
051    boolean isDeclaredVariable(String name);
052
053    /**
054     * Removes an existing variable. May throw UnsupportedOperationException.
055     *
056     * @param name is a variable name without the "$" sign
057     */
058    void undeclareVariable(String name);
059}