1 /* 2 * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * 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) throws java.sql.SQLException; 79 80 } 81
