01 /*
02 * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
03 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
04 *
05 * This code is free software; you can redistribute it and/or modify it
06 * under the terms of the GNU General Public License version 2 only, as
07 * published by the Free Software Foundation. Sun designates this
08 * particular file as subject to the "Classpath" exception as provided
09 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.sql;
27
28 /**
29 * Interface for JDBC classes which provide the ability to retrieve the delegate instance when the instance
30 * in question is in fact a proxy class.
31 * <p>
32 * The wrapper pattern is employed by many JDBC driver implementations to provide extensions beyond
33 * the traditional JDBC API that are specific to a data source. Developers may wish to gain access to
34 * these resources that are wrapped (the delegates) as proxy class instances representing the
35 * the actual resources. This interface describes a standard mechanism to access
36 * these wrapped resources
37 * represented by their proxy, to permit direct access to the resource delegates.
38 *
39 * @since 1.6
40 */
41
42 public interface Wrapper {
43
44 /**
45 * Returns an object that implements the given interface to allow access to
46 * non-standard methods, or standard methods not exposed by the proxy.
47 *
48 * If the receiver implements the interface then the result is the receiver
49 * or a proxy for the receiver. If the receiver is a wrapper
50 * and the wrapped object implements the interface then the result is the
51 * wrapped object or a proxy for the wrapped object. Otherwise return the
52 * the result of calling <code>unwrap</code> recursively on the wrapped object
53 * or a proxy for that result. If the receiver is not a
54 * wrapper and does not implement the interface, then an <code>SQLException</code> is thrown.
55 *
56 * @param iface A Class defining an interface that the result must implement.
57 * @return an object that implements the interface. May be a proxy for the actual implementing object.
58 * @throws java.sql.SQLException If no object found that implements the interface
59 * @since 1.6
60 */
61 <T> T unwrap(java.lang.Class<T> iface) throws java.sql.SQLException;
62
63 /**
64 * Returns true if this either implements the interface argument or is directly or indirectly a wrapper
65 * for an object that does. Returns false otherwise. If this implements the interface then return true,
66 * else if this is a wrapper then return the result of recursively calling <code>isWrapperFor</code> on the wrapped
67 * object. If this does not implement the interface and is not a wrapper, return false.
68 * This method should be implemented as a low-cost operation compared to <code>unwrap</code> so that
69 * callers can use this method to avoid expensive <code>unwrap</code> calls that may fail. If this method
70 * returns true then calling <code>unwrap</code> with the same argument should succeed.
71 *
72 * @param iface a Class defining an interface.
73 * @return true if this implements the interface or directly or indirectly wraps an object that does.
74 * @throws java.sql.SQLException if an error occurs while determining whether this is a wrapper
75 * for an object with the given interface.
76 * @since 1.6
77 */
78 boolean isWrapperFor(java.lang.Class<?> iface)
79 throws java.sql.SQLException;
80
81 }
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