generalcacheadministrator.java

来自「一个不错的cache」· Java 代码 · 共 300 行

/*
 * Copyright (c) 2002-2003 by OpenSymphony
 * All rights reserved.
 */
package com.opensymphony.oscache.general;

import com.opensymphony.oscache.base.*;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.Date;
import java.util.Properties;

/**
 * A GeneralCacheAdministrator creates, flushes and administers the cache.
 *
 * EXAMPLES :
 * <pre><code>
 * // ---------------------------------------------------------------
 * // Typical use with fail over
 * // ---------------------------------------------------------------
 * String myKey = "myKey";
 * String myValue;
 * int myRefreshPeriod = 1000;
 * try {
 *     // Get from the cache
 *     myValue = (String) admin.getFromCache(myKey, myRefreshPeriod);
 * } catch (NeedsRefreshException nre) {
 *     try {
 *         // Get the value (probably by calling an EJB)
 *         myValue = "This is the content retrieved.";
 *         // Store in the cache
 *         admin.putInCache(myKey, myValue);
 *     } catch (Exception ex) {
 *         // We have the current content if we want fail-over.
 *         myValue = (String) nre.getCacheContent();
 *         // It is essential that cancelUpdate is called if the
 *         // cached content is not rebuilt
 *         admin.cancelUpdate(myKey);
 *     }
 * }
 *
 *
 *
 * // ---------------------------------------------------------------
 * // Typical use without fail over
 * // ---------------------------------------------------------------
 * String myKey = "myKey";
 * String myValue;
 * int myRefreshPeriod = 1000;
 * try {
 *     // Get from the cache
 *     myValue = (String) admin.getFromCache(myKey, myRefreshPeriod);
 * } catch (NeedsRefreshException nre) {
 *     try {
 *         // Get the value (probably by calling an EJB)
 *         myValue = "This is the content retrieved.";
 *         // Store in the cache
 *         admin.putInCache(myKey, myValue);
 *         updated = true;
 *     } finally {
 *         if (!updated) {
 *             // It is essential that cancelUpdate is called if the
 *             // cached content could not be rebuilt
 *             admin.cancelUpdate(myKey);
 *         }
 *     }
 * }
 * // ---------------------------------------------------------------
 * // ---------------------------------------------------------------
 * </code></pre>
 *
 * @version        $Revision: 1.9 $
 * @author <a href="mailto:[e-mail]">Francois Beauregard</a>
 * @author <a href="mailto:[e-mail]">Alain Bergevin</a>
 */
public class GeneralCacheAdministrator extends AbstractCacheAdministrator {
    private static transient final Log log = LogFactory.getLog(GeneralCacheAdministrator.class);

    /**
     * Application cache
     */
    private Cache applicationCache = null;

    /**
     * Create the cache administrator.
     */
    public GeneralCacheAdministrator() {
        this(null);
    }

    /**
     * Create the cache administrator with the specified properties
     */
    public GeneralCacheAdministrator(Properties p) {
        super(p);
        log.info("Constructed GeneralCacheAdministrator()");
        createCache();
    }

    /**
     * Grabs a cache
     *
     * @return The cache
     */
    public Cache getCache() {
        return applicationCache;
    }

    /**
     * Get an object from the cache
     *
     * @param key             The key entered by the user.
     * @return   The object from cache
     * @throws NeedsRefreshException when no cache entry could be found with the
     * supplied key, or when an entry was found but is considered out of date. If
     * the cache entry is a new entry that is currently being constructed this method
     * will block until the new entry becomes available. Similarly, it will block if
     * a stale entry is currently being rebuilt by another thread and cache blocking is
     * enabled (<code>cache.blocking=true</code>).
     */
    public Object getFromCache(String key) throws NeedsRefreshException {
        return getCache().getFromCache(key);
    }

    /**
     * Get an object from the cache
     *
     * @param key             The key entered by the user.
     * @param refreshPeriod   How long the object can stay in cache in seconds. To
     * allow the entry to stay in the cache indefinitely, supply a value of
     * {@link CacheEntry#INDEFINITE_EXPIRY}
     * @return   The object from cache
     * @throws NeedsRefreshException when no cache entry could be found with the
     * supplied key, or when an entry was found but is considered out of date. If
     * the cache entry is a new entry that is currently being constructed this method
     * will block until the new entry becomes available. Similarly, it will block if
     * a stale entry is currently being rebuilt by another thread and cache blocking is
     * enabled (<code>cache.blocking=true</code>).
     */
    public Object getFromCache(String key, int refreshPeriod) throws NeedsRefreshException {
        return getCache().getFromCache(key, refreshPeriod);
    }

    /**
     * Get an object from the cache
     *
     * @param key             The key entered by the user.
     * @param refreshPeriod   How long the object can stay in cache in seconds. To
     * allow the entry to stay in the cache indefinitely, supply a value of
     * {@link CacheEntry#INDEFINITE_EXPIRY}
     * @param cronExpression  A cron expression that the age of the cache entry
     * will be compared to. If the entry is older than the most recent match for the
     * cron expression, the entry will be considered stale.
     * @return   The object from cache
     * @throws NeedsRefreshException when no cache entry could be found with the
     * supplied key, or when an entry was found but is considered out of date. If
     * the cache entry is a new entry that is currently being constructed this method
     * will block until the new entry becomes available. Similarly, it will block if
     * a stale entry is currently being rebuilt by another thread and cache blocking is
     * enabled (<code>cache.blocking=true</code>).
     */
    public Object getFromCache(String key, int refreshPeriod, String cronExpression) throws NeedsRefreshException {
        return getCache().getFromCache(key, refreshPeriod, cronExpression);
    }

    /**
     * Cancels a pending cache update. This should only be called by a thread
     * that received a {@link NeedsRefreshException} and was unable to generate
     * some new cache content.
     *
     * @param key The cache entry key to cancel the update of.
     */
    public void cancelUpdate(String key) {
        getCache().cancelUpdate(key);
    }

    /**
     * Shuts down the cache administrator.
     */
    public void destroy() {
        finalizeListeners(applicationCache);
    }

    // METHODS THAT DELEGATES TO THE CACHE ---------------------

    /**
     * Flush the entire cache immediately.
     */
    public void flushAll() {
        getCache().flushAll(new Date());
    }

    /**
     * Flush the entire cache at the given date.
     *
     * @param date The time to flush
     */
    public void flushAll(Date date) {
        getCache().flushAll(date);
    }

    /**
     * Flushes a single cache entry.
     */
    public void flushEntry(String key) {
        getCache().flushEntry(key);
    }

    /**
     * Flushes all items that belong to the specified group.
     *
     * @param group The name of the group to flush
     */
    public void flushGroup(String group) {
        getCache().flushGroup(group);
    }

    /**
     * Allows to flush all items that have a specified pattern in the key.
     *
     * @param pattern     Pattern.
     * @deprecated For performance and flexibility reasons it is preferable to
     * store cache entries in groups and use the {@link #flushGroup(String)} method
     * instead of relying on pattern flushing.
     */
    public void flushPattern(String pattern) {
        getCache().flushPattern(pattern);
    }

    /**
     * Put an object in a cache
     *
     * @param key       The key entered by the user
     * @param content   The object to store
     * @param policy    Object that implements refresh policy logic
     */
    public void putInCache(String key, Object content, EntryRefreshPolicy policy) {
        Cache cache = getCache();
        cache.putInCache(key, content, policy);
    }

    /**
     * Put an object in a cache
     *
     * @param key       The key entered by the user
     * @param content   The object to store
     */
    public void putInCache(String key, Object content) {
        putInCache(key, content, (EntryRefreshPolicy) null);
    }

    /**
     * Puts an object in a cache
     *
     * @param key      The unique key for this cached object
     * @param content  The object to store
     * @param groups   The groups that this object belongs to
     */
    public void putInCache(String key, Object content, String[] groups) {
        getCache().putInCache(key, content, groups);
    }

    /**
     * Puts an object in a cache
     *
     * @param key      The unique key for this cached object
     * @param content  The object to store
     * @param groups   The groups that this object belongs to
     * @param policy   The refresh policy to use
     */
    public void putInCache(String key, Object content, String[] groups, EntryRefreshPolicy policy) {
        getCache().putInCache(key, content, groups, policy, null);
    }

    /**
     * Sets the cache capacity (number of items). If the cache contains
     * more than <code>capacity</code> items then items will be removed
     * to bring the cache back down to the new size.
     *
     * @param capacity The new capacity of the cache
     */
    public void setCacheCapacity(int capacity) {
        super.setCacheCapacity(capacity);
        getCache().setCapacity(capacity);
    }

    /**
     * Creates a cache in this admin
     */
    private void createCache() {
        log.info("Creating new cache");

        applicationCache = new Cache(isMemoryCaching(), isUnlimitedDiskCache(), isOverflowPersistence(), isBlocking(), algorithmClass, cacheCapacity);

        configureStandardListeners(applicationCache);
    }
}