01: /*
02: * Licensed to the Apache Software Foundation (ASF) under one or more
03: * contributor license agreements. See the NOTICE file distributed with
04: * this work for additional information regarding copyright ownership.
05: * The ASF licenses this file to You under the Apache License, Version 2.0
06: * (the "License"); you may not use this file except in compliance with
07: * the License. You may obtain a copy of the License at
08: *
09: * 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: }
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