/interpreter/tags/at2dist091109/src/edu/vub/at/objects/ATHandler.java

 1/**
 2 * AmbientTalk/2 Project
 3 * ATHandler.java created on Sep 26, 2006 at 7:56:45 PM
 4 * (c) Programming Technology Lab, 2006 - 2007
 5 * Authors: Tom Van Cutsem & Stijn Mostinckx
 6 * 
 7 * Permission is hereby granted, free of charge, to any person
 8 * obtaining a copy of this software and associated documentation
 9 * files (the "Software"), to deal in the Software without
10 * restriction, including without limitation the rights to use,
11 * copy, modify, merge, publish, distribute, sublicense, and/or
12 * sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following
14 * conditions:
15 *
16 * The above copyright notice and this permission notice shall be
17 * included in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
26 * OTHER DEALINGS IN THE SOFTWARE.
27 */
28package edu.vub.at.objects;
29
30import edu.vub.at.exceptions.InterpreterException;
31
32/**
33 * ATHandler represents a first-class exception handler which have a filter object, 
34 * describing the kind of exceptions caught by the handler and a code block which 
35 * acts as replacement code for the code that raised the exception.
36 *
37 * @author smostinc
38 */
39public interface ATHandler extends ATObject {
40	
41	/**
42	 * Returns whether a handler will be triggered when an exception is raised.
43	 * <p>
44	 * The primary use of this method is to provide a hook to deviate from the default semantics, which is:
45	 * <p>
46	 * <code>
47	 * def canHandle(anException) {
48	 *   (reflect: anException).isCloneOf(filter);
49	 * };
50	 * </code>
51	 * 
52	 * @param exception an exception.
53	 * @return true if the receiver handle will be triggered when the exception is raised.
54	 */
55	public ATBoolean base_canHandle(ATObject exception) throws InterpreterException;
56	
57	/**
58	 * Evaluates the associated handler closure if the handler can handle the given exception.
59	 * <p>
60	 * When a handler has answered that it can handle an exception, the following
61	 * method is invoked, asking the handler to handle the exception.
62	 * The default semantics is simply to invoke the associated handler closure.
63	 * <p>
64	 * <code>
65	 * def handle(anException) {
66	 *   handler(anException)
67	 * };
68	 * </code>
69	 * 
70	 * @param exception an exception to be handled.
71	 * @return an {@link ATObject} representing the result of evaluating the associated handler closure.
72	 * 
73	 */
74	public ATObject base_handle(ATObject exception) throws InterpreterException;
75}