org.apache.commons.cache.GroupMapImpl.java Source code

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Here is the source code for org.apache.commons.cache.GroupMapImpl.java

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/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.cache;

import java.io.Serializable;
import java.util.HashMap;
import java.util.HashSet;

/**
 * tk.
 * @version $Id: GroupMapImpl.java 155435 2005-02-26 13:17:27Z dirkv $
 * @author Rodney Waldhoff
 */
public class GroupMapImpl extends BaseStorageListener implements GroupMap, StorageListener {
    /** The {@link Cache} I am associated with. */
    protected Cache _cache = null;
    /** A map from groups to a set of associated keys. */
    protected HashMap _groupToKeys = new HashMap();
    /** A map from keys to their groups. */
    protected HashMap _keyToGroup = new HashMap();

    /** Returns an array of key values associated with the given group. */
    public synchronized Serializable[] getKeysForGroup(Serializable group) {
        try {
            HashSet set = (HashSet) (_groupToKeys.get(group));
            return (Serializable[]) (set.toArray(new Serializable[0]));
        } catch (Exception e) {
            return new Serializable[0];
        }
    }

    /** Sets my cache. */
    public void setCache(Cache c) {
        if (null != _cache) {
            Object mutex = _cache;
            synchronized (mutex) {
                synchronized (c) {
                    synchronized (this) {
                        unsetCache();
                        _cache = c;
                        _cache.registerStorageListener(this);
                    }
                }
            }
        } else {
            synchronized (c) {
                synchronized (this) {
                    _cache = c;
                    _cache.registerStorageListener(this);
                }
            }
        }
    }

    /** Unsets my cache. */
    public void unsetCache() {
        if (null != _cache) {
            Object mutex = _cache;
            synchronized (mutex) {
                synchronized (this) {
                    _cache.unregisterStorageListener(this);
                    clear();
                    _cache = null;
                }
            }
        }
    }

    public synchronized void stored(Serializable key, Serializable val, Long expiresAt, Long cost,
            Serializable group) {
        if (null == group) {
            Object oldgroup = _keyToGroup.get(key);
            if (null != oldgroup) {
                HashSet oldset = (HashSet) (_groupToKeys.get(oldgroup));
                if (null != oldset) {
                    oldset.remove(key);
                }
            }
        } else {
            HashSet set = (HashSet) (_groupToKeys.get(group));
            if (null != set) {
                set.add(key);
            } else {
                set = new HashSet();
                set.add(key);
                _groupToKeys.put(group, set);
            }
            Object oldgroup = _keyToGroup.put(key, group);
            if (null != oldgroup && !(oldgroup.equals(group))) {
                HashSet oldset = (HashSet) (_groupToKeys.get(oldgroup));
                if (null != oldset) {
                    oldset.remove(key);
                }
            }
        }
    }

    public synchronized void cleared(Serializable key) {
        Serializable group = (Serializable) (_keyToGroup.remove(key));
        if (null != group) {
            HashSet set = (HashSet) (_groupToKeys.get(group));
            set.remove(key);
        }
    }

    public void cleared() {
        clear();
    }

    protected synchronized void clear() {
        _groupToKeys.clear();
        _keyToGroup.clear();
    }

    public static void main(String[] args) {
        GroupMapImpl tm = new GroupMapImpl();
        tm.stored("key1", "val", null, null, "group1");
        tm.stored("key2", "val", null, null, "group1");
        tm.stored("key3", "val", null, null, "group1");
        tm.stored("key4", "val", null, null, "group1");
        Serializable[] keys = tm.getKeysForGroup("group1");
        for (int i = 0; i < keys.length; i++) {
            System.out.println(keys[i]);
        }
    }
}