Wrapper


1   /**
2    * MEDOR: Middleware Enabling Distributed Object Requests
3    *
4    * Copyright (C) 2001-2003 France Telecom R&D
5    * Contact: alexandre.lefebvre@rd.francetelecom.com
6    *
7    * This library is free software; you can redistribute it and/or
8    * modify it under the terms of the GNU Lesser General Public
9    * License as published by the Free Software Foundation; either
10   * version 2.1 of the License, or (at your option) any later version.
11   *
12   * This library is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15   * Lesser General Public License for more details.
16   *
17   * You should have received a copy of the GNU Lesser General Public
18   * License along with this library; if not, write to the Free Software
19   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20   *
21   * Initial developers: M. Alia, A. Lefebvre, S. Chassande-Barrioz
22   */
23  
24  package org.objectweb.medor.datasource.api;
25  
26  import org.objectweb.medor.api.EvaluationException;
27  import org.objectweb.medor.expression.api.ParameterOperand;
28  import org.objectweb.medor.query.api.QueryLeaf;
29  import org.objectweb.medor.tuple.api.TupleCollection;
30  import org.objectweb.medor.eval.api.EvaluationMetaData;
31  
32  /**
33   * Represents a wrapper to access data from a QueryLeaf at query evaluation
34   * time.
35   * <p>A Wrapper is associated to a QueryLeaf at a given point of time.
36   * There can be several Wrappers of the same type.
37   * One Wrapper can be associated sequentially to several QueryLeaves.
38   *
39   * @author Sebastien Chassande-Barrioz
40   */
41  public interface Wrapper {
42      /**
43       * This method links the wrapper to a particular QueryLeaf, and executes
44       * the query on the underlying data store.
45       * @param ql the QueryLeaf
46       * @param parameters the parameters necessary for obtaining data from the
47       * QueryLeaf (in the case the QueryLeaf contains an expression)
48       * @param connection an Object which contains information for connecting
49       * to the DataStore behind the QueryLeaf (could be a JDBC connection, ...)s
50       * @return the TupleCollection containing the result of the execution.
51       * @throws EvaluationException in case of problems during the evaluation.
52       *
53       */
54      TupleCollection fetchData(QueryLeaf ql,
55                                ParameterOperand[] parameters,
56                                Object   connection,
57                                EvaluationMetaData evalmd)
58          throws EvaluationException;
59  }
60
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