/*
* Copyright (c) 2005, 2006, 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
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*/
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 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;
}