Java tutorial
/* * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.sql; /** * Interface for JDBC classes which provide the ability to retrieve the delegate instance when the instance * in question is in fact a proxy class. * <p> * The wrapper pattern is employed by many JDBC driver implementations to provide extensions beyond * the traditional JDBC API that are specific to a data source. Developers may wish to gain access to * these resources that are wrapped (the delegates) as proxy class instances representing the * the actual resources. This interface describes a standard mechanism to access * these wrapped resources * represented by their proxy, to permit direct access to the resource delegates. * * @since 1.6 */ public interface Wrapper { /** * Returns an object that implements the given interface to allow access to * non-standard methods, or standard methods not exposed by the proxy. * * If the receiver implements the interface then the result is the receiver * or a proxy for the receiver. If the receiver is a wrapper * and the wrapped object implements the interface then the result is the * wrapped object or a proxy for the wrapped object. Otherwise return the * the result of calling <code>unwrap</code> recursively on the wrapped object * or a proxy for that result. If the receiver is not a * wrapper and does not implement the interface, then an <code>SQLException</code> is thrown. * * @param <T> the type of the class modeled by this Class object * @param iface A Class defining an interface that the result must implement. * @return an object that implements the interface. May be a proxy for the actual implementing object. * @throws java.sql.SQLException If no object found that implements the interface * @since 1.6 */ <T> T unwrap(java.lang.Class<T> iface) throws java.sql.SQLException; /** * Returns true if this either implements the interface argument or is directly or indirectly a wrapper * for an object that does. Returns false otherwise. If this implements the interface then return true, * else if this is a wrapper then return the result of recursively calling <code>isWrapperFor</code> on the wrapped * object. If this does not implement the interface and is not a wrapper, return false. * This method should be implemented as a low-cost operation compared to <code>unwrap</code> so that * callers can use this method to avoid expensive <code>unwrap</code> calls that may fail. If this method * returns true then calling <code>unwrap</code> with the same argument should succeed. * * @param iface a Class defining an interface. * @return true if this implements the interface or directly or indirectly wraps an object that does. * @throws java.sql.SQLException if an error occurs while determining whether this is a wrapper * for an object with the given interface. * @since 1.6 */ boolean isWrapperFor(java.lang.Class<?> iface) throws java.sql.SQLException; }