/*

 * Copyright (c) 2003, 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 sun.management.snmp.jvminstr;

// java imports

//

import com.sun.jmx.mbeanserver.Util;

import java.io.Serializable;

import java.util.List;

import java.util.Map;

import java.util.TreeMap;

// jmx imports

//

import com.sun.jmx.snmp.SnmpOid;

import com.sun.jmx.snmp.SnmpStatusException;

// jdmk imports

//

import com.sun.jmx.snmp.agent.SnmpMib;

import com.sun.jmx.snmp.agent.SnmpStandardObjectServer;

import java.lang.management.MemoryManagerMXBean;

import java.lang.management.ManagementFactory;

import sun.management.snmp.jvmmib.JvmMemManagerTableMeta;

import sun.management.snmp.util.SnmpTableCache;

import sun.management.snmp.util.SnmpNamedListTableCache;

import sun.management.snmp.util.SnmpTableHandler;

import sun.management.snmp.util.MibLogger;

import sun.management.snmp.util.JvmContextFactory;

/**

 * The class is used for implementing the "JvmMemManagerTable" table.

 *

 * This custom implementation show how to implement an SNMP table

 * over a weak cache, recomputing the cahed data when needed.

 */

public class JvmMemManagerTableMetaImpl extends JvmMemManagerTableMeta {

    /**

     * A concrete implementation of {@link SnmpNamedListTableCache}, for the

     * jvmMemManagerTable.

     **/

    private static class JvmMemManagerTableCache

        extends SnmpNamedListTableCache {

        /**

         * Create a weak cache for the jvmMemManagerTable.

         * @param validity validity of the cached data, in ms.

         **/

        JvmMemManagerTableCache(long validity) {

            this.validity = validity;

        }

        /**

         * Use the MemoryManagerMXBean name as key.

         * @param context A {@link TreeMap} as allocated by the parent

         *        {@link SnmpNamedListTableCache} class.

         * @param rawDatas List of {@link MemoryManagerMXBean}, as

         *        returned by

         * <code>ManagementFactory.getMemoryMBean().getMemoryManagers()</code>

         * @param rank The <var>rank</var> of <var>item</var> in the list.

         * @param item The <var>rank</var><super>th</super>

         *        <code>MemoryManagerMXBean</code> in the list.

         * @return  <code>((MemoryManagerMXBean)item).getName()</code>

         **/

                                int rank, Object item) {

            if (item == null) return null;

            final String name = ((MemoryManagerMXBean)item).getName();

            log.debug("getKey", "key=" + name);

            return name;

        }

        /**

         * Call <code>getTableHandler(JvmContextFactory.getUserData())</code>.

         **/

        public SnmpTableHandler getTableHandler() {

            return getTableDatas(userData);

        }

        /**

         * Return the key used to cache the raw data of this table.

         **/

        protected String getRawDatasKey() {

            return "JvmMemManagerTable.getMemoryManagers";

        }

        /**

         * Call ManagementFactory.getMemoryManagerMXBeans() to

         * load the raw data of this table.

         **/

            return ManagementFactory.getMemoryManagerMXBeans();

        }

    }

    // The weak cache for this table.

    protected SnmpTableCache cache;

    /**

     * Constructor for the table. Initialize metadata for

     * "JvmMemManagerTableMeta".

     * The reference on the MBean server is updated so the entries

     * created through an SNMP SET will be AUTOMATICALLY REGISTERED

     * in Java DMK.

     */

    public JvmMemManagerTableMetaImpl(SnmpMib myMib,

                                      SnmpStandardObjectServer objserv) {

        super(myMib,objserv);

        this.cache = new

            JvmMemManagerTableCache(((JVM_MANAGEMENT_MIB_IMPL)myMib).

                                    validity());

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    protected SnmpOid getNextOid(Object userData)

        throws SnmpStatusException {

        // null means get the first OID.

        return getNextOid(null,userData);

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    protected SnmpOid getNextOid(SnmpOid oid, Object userData)

        throws SnmpStatusException {

        final boolean dbg = log.isDebugOn();

        if (dbg) log.debug("getNextOid", "previous=" + oid);

        // Get the data handler.

        //

        SnmpTableHandler handler = getHandler(userData);

        if (handler == null) {

            // This should never happen.

            // If we get here it's a bug.

            //

            if (dbg) log.debug("getNextOid", "handler is null!");

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        }

        // Get the next oid

        //

        final SnmpOid next = handler.getNext(oid);

        if (dbg) log.debug("getNextOid", "next=" + next);

        // if next is null: we reached the end of the table.

        //

        if (next == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        return next;

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    protected boolean contains(SnmpOid oid, Object userData) {

        // Get the handler.

        //

        SnmpTableHandler handler = getHandler(userData);

        // handler should never be null.

        //

        if (handler == null)

            return false;

        return handler.contains(oid);

    }

    // See com.sun.jmx.snmp.agent.SnmpMibTable

    public Object getEntry(SnmpOid oid)

        throws SnmpStatusException {

        if (oid == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        // Get the request contextual cache (userData).

        //

        final Map<Object, Object> m = JvmContextFactory.getUserData();

        // We know in the case of this table that the index is an integer,

        // it is thus the first OID arc of the index OID.

        //

        final long   index    = oid.getOidArc(0);

        // We're going to use this name to store/retrieve the entry in

        // the request contextual cache.

        //

        // Revisit: Probably better programming to put all these strings

        //          in some interface.

        //

        final String entryTag = ((m==null)?null:("JvmMemManagerTable.entry." +

                                                 index));

        // If the entry is in the cache, simply return it.

        //

        if (m != null) {

            final Object entry = m.get(entryTag);

            if (entry != null) return entry;

        }

        // The entry was not in the cache, make a new one.

        //

        // Get the data hanler.

        //

        SnmpTableHandler handler = getHandler(m);

        // handler should never be null.

        //

        if (handler == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        // Get the data associated with our entry.

        //

        final Object data = handler.getData(oid);

        // data may be null if the OID we were given is not valid.

        //

        if (data == null)

            throw new SnmpStatusException(SnmpStatusException.noSuchInstance);

        // make the new entry (transient object that will be kept only

        // for the duration of the request.

        //

        final Object entry =

            new JvmMemManagerEntryImpl((MemoryManagerMXBean)data,(int)index);

        // Put the entry in the cache in case we need it later while processing

        // the request.

        //

        if (m != null && entry != null) {

            m.put(entryTag,entry);

        }

        return entry;

    }

    /**

     * Get the SnmpTableHandler that holds the jvmMemManagerTable data.

     * First look it up in the request contextual cache, and if it is

     * not found, obtain it from the weak cache.

     * <br>The request contextual cache will be released at the end of the

     * current requests, and is used only to process this request.

     * <br>The weak cache is shared by all requests, and is only

     * recomputed when it is found to be obsolete.

     * <br>Note that the data put in the request contextual cache is

     *     never considered to be obsolete, in order to preserve data

     *     coherency.

     **/

    protected SnmpTableHandler getHandler(Object userData) {

        final Map<Object, Object> m;

        if (userData instanceof Map) m=Util.cast(userData);

        else m=null;

        // Look in the contextual cache.

        if (m != null) {

            final SnmpTableHandler handler =

                (SnmpTableHandler)m.get("JvmMemManagerTable.handler");

            if (handler != null) return handler;

        }

        // No handler in contextual cache, make a new one.

        final SnmpTableHandler handler = cache.getTableHandler();

        if (m != null && handler != null )

            m.put("JvmMemManagerTable.handler",handler);

        return handler;

    }

    static final MibLogger log =

        new MibLogger(JvmMemManagerTableMetaImpl.class);

}