1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.scxml;
18
19 import org.w3c.dom.Node;
20
21 /**
22 * Interface for a component that may be used by the SCXML engines to
23 * evaluate the expressions within the SCXML document.
24 *
25 */
26 public interface Evaluator {
27
28 /**
29 * Evaluate an expression.
30 *
31 * @param ctx variable context
32 * @param expr expression
33 * @return a result of the evaluation
34 * @throws SCXMLExpressionException A malformed exception
35 */
36 Object eval(Context ctx, String expr)
37 throws SCXMLExpressionException;
38
39 /**
40 * Evaluate a condition.
41 * Manifests as "cond" attributes of <transition>,
42 * <if> and <elseif> elements.
43 *
44 * @param ctx variable context
45 * @param expr expression
46 * @return true/false
47 * @throws SCXMLExpressionException A malformed exception
48 */
49 Boolean evalCond(Context ctx, String expr)
50 throws SCXMLExpressionException;
51
52 /**
53 * Evaluate a location that returns a Node within an XML data tree.
54 * Manifests as "location" attributes of <assign> element.
55 *
56 * @param ctx variable context
57 * @param expr expression
58 * @return The location node.
59 * @throws SCXMLExpressionException A malformed exception
60 */
61 Node evalLocation(Context ctx, String expr)
62 throws SCXMLExpressionException;
63
64 /**
65 * Create a new child context.
66 *
67 * @param parent parent context
68 * @return new child context
69 */
70 Context newContext(Context parent);
71
72 }
73