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.scxml;
018
019 import org.w3c.dom.Node;
020
021 /**
022 * Interface for a component that may be used by the SCXML engines to
023 * evaluate the expressions within the SCXML document.
024 *
025 */
026 public interface Evaluator {
027
028 /**
029 * Evaluate an expression.
030 *
031 * @param ctx variable context
032 * @param expr expression
033 * @return a result of the evaluation
034 * @throws SCXMLExpressionException A malformed exception
035 */
036 Object eval(Context ctx, String expr)
037 throws SCXMLExpressionException;
038
039 /**
040 * Evaluate a condition.
041 * Manifests as "cond" attributes of <transition>,
042 * <if> and <elseif> elements.
043 *
044 * @param ctx variable context
045 * @param expr expression
046 * @return true/false
047 * @throws SCXMLExpressionException A malformed exception
048 */
049 Boolean evalCond(Context ctx, String expr)
050 throws SCXMLExpressionException;
051
052 /**
053 * Evaluate a location that returns a Node within an XML data tree.
054 * Manifests as "location" attributes of <assign> element.
055 *
056 * @param ctx variable context
057 * @param expr expression
058 * @return The location node.
059 * @throws SCXMLExpressionException A malformed exception
060 */
061 Node evalLocation(Context ctx, String expr)
062 throws SCXMLExpressionException;
063
064 /**
065 * Create a new child context.
066 *
067 * @param parent parent context
068 * @return new child context
069 */
070 Context newContext(Context parent);
071
072 }
073