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 * Copyright (c) 2005, 2020, 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,

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 *

 * 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} 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} 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} 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} so that

     * callers can use this method to avoid expensive {@code unwrap} calls that may fail. If this method

     * returns true then calling {@code unwrap} 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;

}