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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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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 *

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package com.sun.jmx.snmp.agent;

import com.sun.jmx.snmp.SnmpPduPacket;

import com.sun.jmx.snmp.SnmpPdu;

import com.sun.jmx.snmp.SnmpStatusException;

/**

 * This interface is provided to enable fine customization of the SNMP

 * agent behaviour.

 *

 * <p>You will not need to implement this interface except if your agent

 * needs extra customization requiring some contextual information.</p>

 *

 * <p>If an SnmpUserDataFactory is set on the SnmpAdaptorServer, then a new

 * object containing user-data will be allocated through this factory

 * for each incoming request. This object will be passed along to

 * the SnmpMibAgent within SnmpMibRequest objects. By default, no

 * SnmpUserDataFactory is set on the SnmpAdaptorServer, and the contextual

 * object passed to SnmpMibAgent is null.</p>

 *

 * <p>You can use this feature to obtain on contextual information

 * (such as community string etc...) or to implement a caching

 * mechanism, or for whatever purpose might be required by your specific

 * agent implementation.</p>

 *

 * <p>The sequence <code>allocateUserData() / releaseUserData()</code> can

 * also be used to implement a caching mechanism:

 * <ul>

 * <li><code>allocateUserData()</code> could be used to allocate

 *         some cache space,</li>

 * <li>and <code>releaseUserData()</code> could be used to flush it.</li>

 * </ul></p>

 *

 * <p><b>This API is a Sun Microsystems internal API  and is subject

 * to change without notice.</b></p>

 * @see com.sun.jmx.snmp.agent.SnmpMibRequest

 * @see com.sun.jmx.snmp.agent.SnmpMibAgent

 * @see com.sun.jmx.snmp.daemon.SnmpAdaptorServer

 *

 **/

public interface SnmpUserDataFactory {

    /**

     * Called by the <CODE>SnmpAdaptorServer</CODE> adaptor.

     * Allocate a contextual object containing some user data. This method

     * is called once for each incoming SNMP request. The scope

     * of this object will be the whole request. Since the request can be

     * handled in several threads, the user should make sure that this

     * object can be accessed in a thread-safe manner. The SNMP framework

     * will never access this object directly - it will simply pass

     * it to the <code>SnmpMibAgent</code> within

     * <code>SnmpMibRequest</code> objects - from where it can be retrieved

     * through the {@link com.sun.jmx.snmp.agent.SnmpMibRequest#getUserData() getUserData()} accessor.

     * <code>null</code> is considered to be a valid return value.

     *

     * This method is called just after the SnmpPduPacket has been

     * decoded.

     *

     * @param requestPdu The SnmpPduPacket received from the SNMP manager.

     *        <b>This parameter is owned by the SNMP framework and must be

     *        considered as transient.</b> If you wish to keep some of its

     *        content after this method returns (by storing it in the

     *        returned object for instance) you should clone that

     *        information.

     *

     * @return A newly allocated user-data contextual object, or

     *         <code>null</code>

     * @exception SnmpStatusException If an SnmpStatusException is thrown,

     *            the request will be aborted.

     *

     * @since 1.5

     **/

    public Object allocateUserData(SnmpPdu requestPdu)

        throws SnmpStatusException;

    /**

     * Called by the <CODE>SnmpAdaptorServer</CODE> adaptor.

     * Release a previously allocated contextual object containing user-data.

     * This method is called just before the responsePdu is sent back to the

     * manager. It gives the user a chance to alter the responsePdu packet

     * before it is encoded, and to free any resources that might have

     * been allocated when creating the contextual object.

     *

     * @param userData The contextual object being released.

     * @param responsePdu The SnmpPduPacket that will be sent back to the

     *        SNMP manager.

     *        <b>This parameter is owned by the SNMP framework and must be

     *        considered as transient.</b> If you wish to keep some of its

     *        content after this method returns you should clone that

     *        information.

     *

     * @exception SnmpStatusException If an SnmpStatusException is thrown,

     *            the responsePdu is dropped and nothing is returned to

     *            to the manager.

     *

     * @since 1.5

     **/

    public void releaseUserData(Object userData, SnmpPdu responsePdu)

        throws SnmpStatusException;

}