1 package org.codehaus.plexus.interpolation;
2
3 import java.util.List;
4
5 /*
6 * Copyright 2001-2008 Codehaus Foundation.
7 *
8 * Licensed under the Apache License, Version 2.0 (the "License");
9 * you may not use this file except in compliance with the License.
10 * You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20
21 /**
22 * Logs expressions before resolution is attempted, and clears them
23 * after resolution is complete (or, fails all strategies). In between,
24 * if the value of an expression contains more expressions, RecursionInterceptor
25 * implementations ensure that those expressions don't reference an expression
26 * which is in the process of being resolved. If that happens, the expression
27 * references are cyclical, and would otherwise result in an infinite loop.
28 */
29 public interface RecursionInterceptor {
30
31 /**
32 * Log the intention to start resolving the given expression. This signals
33 * the interceptor to start tracking that expression to make sure it doesn't
34 * come up again until after it has been resolved (or, fails to resolve).
35 *
36 * @param expression The expression to be resolved.
37 */
38 void expressionResolutionStarted(String expression);
39
40 /**
41 * Signal to the interceptor that the all efforts to resolve the given
42 * expression have completed - whether successfully or not is irrelevant -
43 * and that the expression should not be tracked for recursion any longer.
44 *
45 * @param expression The expression to stop tracking.
46 */
47 void expressionResolutionFinished(String expression);
48
49 /**
50 * Check whether the given value contains an expression that is currently
51 * being tracked by this interceptor. If so, that expression is still in
52 * the process of being resolved, and this constitutes an expression cycle.
53 *
54 * @param value The value to check for expression cycles.
55 * @return True if the value contains tracked expressions; false otherwise.
56 */
57 boolean hasRecursiveExpression(String value);
58
59 /**
60 * @return The list of expressions that participate in the cycle caused by
61 * the given expression.
62 * @param expression the expression to start with.
63 */
64 List getExpressionCycle(String expression);
65
66 /**
67 * Reset the interceptor
68 */
69 public void clear();
70 }