01: /* Copyright (C) 2004 - 2007 db4objects Inc. http://www.db4o.com
02:
03: This file is part of the db4o open source object database.
04:
05: db4o is free software; you can redistribute it and/or modify it under
06: the terms of version 2 of the GNU General Public License as published
07: by the Free Software Foundation and as clarified by db4objects' GPL
08: interpretation policy, available at
09: http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10: Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11: Suite 350, San Mateo, CA 94403, USA.
12:
13: db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14: WARRANTY; without even the implied warranty of MERCHANTABILITY or
15: FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16: for more details.
17:
18: You should have received a copy of the GNU General Public License along
19: with this program; if not, write to the Free Software Foundation, Inc.,
20: 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21: package com.db4o.query;
22:
23: /**
24: * for implementation of callback evaluations.
25: * <br><br>
26: * To constrain a {@link Query} node with your own callback
27: * <code>Evaluation</code>, construct an object that implements the
28: * <code>Evaluation</code> interface and register it by passing it
29: * to {@link Query#constrain(Object)}.
30: * <br><br>
31: * Evaluations are called as the last step during query execution,
32: * after all other constraints have been applied. Evaluations in higher
33: * level {@link Query} nodes in the query graph are called first.
34: * <br><br>Java client/server only:<br>
35: * db4o first attempts to use Java Serialization to allow to pass final
36: * variables to the server. Please make sure that all variables that are
37: * used within the evaluate() method are Serializable. This may include
38: * the class an anonymous Evaluation object is created in. If db4o is
39: * not successful at using Serialization, the Evaluation is transported
40: * to the server in a db4o MemoryFile. In this case final variables can
41: * not be restored.
42: */
43: public interface Evaluation extends java.io.Serializable {
44:
45: /**
46: * callback method during {@link Query#execute() query execution}.
47: * @param candidate reference to the candidate persistent object.
48: */
49: public void evaluate(Candidate candidate);
50:
51: }
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