Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.scxml; import org.w3c.dom.Node; /** * Interface for a component that may be used by the SCXML engines to * evaluate the expressions within the SCXML document. * */ public interface Evaluator { /** * Evaluate an expression. * * @param ctx variable context * @param expr expression * @return a result of the evaluation * @throws SCXMLExpressionException A malformed exception */ Object eval(Context ctx, String expr) throws SCXMLExpressionException; /** * Evaluate a condition. * Manifests as "cond" attributes of <transition>, * <if> and <elseif> elements. * * @param ctx variable context * @param expr expression * @return true/false * @throws SCXMLExpressionException A malformed exception */ Boolean evalCond(Context ctx, String expr) throws SCXMLExpressionException; /** * Evaluate a location that returns a Node within an XML data tree. * Manifests as "location" attributes of <assign> element. * * @param ctx variable context * @param expr expression * @return The location node. * @throws SCXMLExpressionException A malformed exception */ Node evalLocation(Context ctx, String expr) throws SCXMLExpressionException; /** * Evaluate a script. * Manifests as <script> element. * * @param ctx variable context * @param script The script * @return The result of the script execution. * @throws SCXMLExpressionException A malformed script */ Object evalScript(Context ctx, String script) throws SCXMLExpressionException; /** * Create a new child context. * * @param parent parent context * @return new child context */ Context newContext(Context parent); }