    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