servletcacheadministrator.java

来自「一个不错的cache」· Java 代码 · 共 744 行 · 第 1/2 页

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

import com.opensymphony.oscache.base.*;
import com.opensymphony.oscache.base.events.CacheEventListener;
import com.opensymphony.oscache.base.events.ScopeEvent;
import com.opensymphony.oscache.base.events.ScopeEventListener;
import com.opensymphony.oscache.base.events.ScopeEventType;

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

import java.io.Serializable;

import java.util.*;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.PageContext;

/**
 * A ServletCacheAdministrator creates, flushes and administers the cache.
 * <p>
 * This is a "servlet Singleton". This means it's not a Singleton in the traditional sense,
 * that is stored in a static instance. It's a Singleton _per web app context_.
 * <p>
 * Once created it manages the cache path on disk through the oscache.properties
 * file, and also keeps track of the flush times.
 *
 * @author <a href="mailto:[e-mail]">Mike Cannon-Brookes</a>
 * @author <a href="mailto:[e-mail]">Todd Gochenour</a>
 * @author <a href="mailto:[e-mail]">Francois Beauregard</a>
 * @author <a href="mailto:[e-mail]">Alain Bergevin</a>
 * @author <a href="&#109;a&#105;&#108;&#116;&#111;:chris&#64;swebtec.&#99;&#111;&#109;">Chris Miller</a>
 * @version        $Revision: 1.11 $
 */
public class ServletCacheAdministrator extends AbstractCacheAdministrator implements Serializable {
    private static final transient Log log = LogFactory.getLog(ServletCacheAdministrator.class);

    /**
    * Constants for properties read/written from/to file
    */
    private final static String CACHE_USE_HOST_DOMAIN_KEY = "cache.use.host.domain.in.key";
    private final static String CACHE_KEY_KEY = "cache.key";

    /**
    * The default cache key that is used to store the cache in context.
    */
    private final static String DEFAULT_CACHE_KEY = "__oscache_cache";

    /**
    * Constants for scope's name
    */
    public final static String SESSION_SCOPE_NAME = "session";
    public final static String APPLICATION_SCOPE_NAME = "application";

    /**
    * The key under which the CacheAdministrator will be stored in the ServletContext
    */
    private final static String CACHE_ADMINISTRATOR_KEY = "__oscache_admin";

    /**
    * Key used to store the current scope in the configuration. This is a hack
    * to let the scope information get passed through to the DiskPersistenceListener,
    * and will be removed in a future release.
    */
    public final static String HASH_KEY_SCOPE = "scope";

    /**
    * Key used to store the current session ID in the configuration. This is a hack
    * to let the scope information get passed through to the DiskPersistenceListener,
    * and will be removed in a future release.
    */
    public final static String HASH_KEY_SESSION_ID = "sessionId";

    /**
    * Key used to store the servlet container temporary directory in the configuration.
    * This is a hack to let the scope information get passed through to the
    * DiskPersistenceListener, and will be removed in a future release.
    */
    public final static String HASH_KEY_CONTEXT_TMPDIR = "context.tempdir";

    /**
    * The string to use as a file separator.
    */
    private final static String FILE_SEPARATOR = "/";

    /**
    * The character to use as a file separator.
    */
    private final static char FILE_SEPARATOR_CHAR = FILE_SEPARATOR.charAt(0);

    /**
    * Constant for Key generation.
    */
    private final static short AVERAGE_KEY_LENGTH = 30;

    /**
    * Usable caracters for key generation
    */
    private static final String m_strBase64Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    /**
    * Map containing the flush times of different scopes
    */
    private Map flushTimes;

    //private transient ServletContext context;

    /**
    * Key to use for storing and retrieving Object in contexts (Servlet, session).
    */
    private String cacheKey;

    /**
    *  Set property cache.use.host.domain.in.key=true to add domain information to key
    *  generation for hosting multiple sites.
    */
    private boolean useHostDomainInKey = false;

    /**
    *        Create the cache administrator.
    *
    *        This will reset all the flush times and load the properties file.
    */
    private ServletCacheAdministrator(ServletContext context, Properties p) {
        super(p);
        config.set(HASH_KEY_CONTEXT_TMPDIR, context.getAttribute("javax.servlet.context.tempdir"));

        //this.context = context;
        flushTimes = new HashMap();
        initHostDomainInKey();
    }

    /**
    * Obtain an instance of the CacheAdministrator
    *
    * @param context The ServletContext that this CacheAdministrator is a Singleton under
    * @return Returns the CacheAdministrator instance for this context
    */
    public static ServletCacheAdministrator getInstance(ServletContext context) {
        return getInstance(context, null);
    }

    /**
    * Obtain an instance of the CacheAdministrator
    *
    * @param context The ServletContext that this CacheAdministrator is a Singleton under
    * @param p the properties to use for the cache if the cache administrator has not been
    * created yet. Once the administrator has been created, the properties parameter is
    * ignored for all future invocations. If a null value is passed in, then the properties
    * are loaded from the oscache.properties file in the classpath.
    * @return Returns the CacheAdministrator instance for this context
    */
    public static ServletCacheAdministrator getInstance(ServletContext context, Properties p) {
        ServletCacheAdministrator admin;
        admin = (ServletCacheAdministrator) context.getAttribute(CACHE_ADMINISTRATOR_KEY);

        // First time we need to create the administrator and store it in the
        // servlet context
        if (admin == null) {
            admin = new ServletCacheAdministrator(context, p);
            context.setAttribute(CACHE_ADMINISTRATOR_KEY, admin);

            if (log.isInfoEnabled()) {
                log.info("Created new instance of ServletCacheAdministrator");
            }

            admin.getAppScopeCache(context);
        }

        return admin;
    }

    /**
    * Shuts down the cache administrator. This should usually only be called
    * when the controlling application shuts down.
    */
    public static void destroyInstance(ServletContext context) {
        ServletCacheAdministrator admin;
        admin = (ServletCacheAdministrator) context.getAttribute(CACHE_ADMINISTRATOR_KEY);

        if (admin != null) {
            // Finalize the application scope cache
            Cache cache = (Cache) context.getAttribute(admin.getCacheKey());

            if (cache != null) {
                admin.finalizeListeners(cache);
                context.removeAttribute(admin.getCacheKey());
                context.removeAttribute(CACHE_ADMINISTRATOR_KEY);
                cache = null;

                if (log.isInfoEnabled()) {
                    log.info("Shut down the ServletCacheAdministrator");
                }
            }

            admin = null;
        }
    }

    /**
    * Grabs the cache for the specified scope
    *
    * @param request The current request
    * @param scope The scope of this cache (<code>PageContext.APPLICATION_SCOPE</code>
    * or <code>PageContext.SESSION_SCOPE</code>)
    * @return The cache
    */
    public Cache getCache(HttpServletRequest request, int scope) {
        if (scope == PageContext.APPLICATION_SCOPE) {
            return getAppScopeCache(request.getSession(true).getServletContext());
        }

        if (scope == PageContext.SESSION_SCOPE) {
            return getSessionScopeCache(request.getSession(true));
        }

        throw new RuntimeException("The supplied scope value of " + scope + " is invalid. Acceptable values are PageContext.APPLICATION_SCOPE and PageContext.SESSION_SCOPE");
    }

    /**
    * A convenience method to retrieve the application scope cache

    * @param context the current <code>ServletContext</code>
    * @return the application scope cache. If none is present, one will
    * be created.
    */
    public Cache getAppScopeCache(ServletContext context) {
        Cache cache;
        Object obj = context.getAttribute(getCacheKey());

        if ((obj == null) || !(obj instanceof Cache)) {
            if (log.isInfoEnabled()) {
                log.info("Created new application-scoped cache at key: " + getCacheKey());
            }

            cache = createCache(PageContext.APPLICATION_SCOPE, null);
            context.setAttribute(getCacheKey(), cache);
        } else {
            cache = (Cache) obj;
        }

        return cache;
    }

    /**
    * A convenience method to retrieve the session scope cache
    *
    * @param session the current <code>HttpSession</code>
    * @return the session scope cache for this session. If none is present,
    * one will be created.
    */
    public Cache getSessionScopeCache(HttpSession session) {
        Cache cache;
        Object obj = session.getAttribute(getCacheKey());

        if ((obj == null) || !(obj instanceof Cache)) {
            if (log.isInfoEnabled()) {
                log.info("Created new session-scoped cache in session " + session.getId() + " at key: " + getCacheKey());
            }

            cache = createCache(PageContext.SESSION_SCOPE, session.getId());
            session.setAttribute(getCacheKey(), cache);
        } else {
            cache = (Cache) obj;
        }

        return cache;
    }

    /**
    * Get the cache key from the properties. Set it to a default value if it
    * is not present in the properties
    *
    * @return The cache.key property or the DEFAULT_CACHE_KEY
    */
    public String getCacheKey() {
        if (cacheKey == null) {
            cacheKey = getProperty(CACHE_KEY_KEY);

            if (cacheKey == null) {
                cacheKey = DEFAULT_CACHE_KEY;
            }
        }

        return cacheKey;
    }

    /**
    * Set the flush time for a specific scope to a specific time
    *
    * @param date  The time to flush the scope
    * @param scope The scope to be flushed
    */
    public void setFlushTime(Date date, int scope) {
        if (log.isInfoEnabled()) {
            log.info("Flushing scope " + scope + " at " + date);
        }

        synchronized (flushTimes) {
            if (date != null) {
                // Trigger a SCOPE_FLUSHED event
                dispatchScopeEvent(ScopeEventType.SCOPE_FLUSHED, scope, date, null);
                flushTimes.put(new Integer(scope), date);
            } else {
                logError("setFlushTime called with a null date.");
                throw new IllegalArgumentException("setFlushTime called with a null date.");
            }
        }
    }

    /**
    * Set the flush time for a specific scope to the current time.
    *
    * @param scope The scope to be flushed
    */
    public void setFlushTime(int scope) {
        setFlushTime(new Date(), scope);
    }

    /**
    *        Get the flush time for a particular scope.
    *
    *        @param        scope        The scope to get the flush time for.
    *        @return A date representing the time this scope was last flushed.
    *        Returns null if it has never been flushed.
    */
    public Date getFlushTime(int scope) {
        synchronized (flushTimes) {
            return (Date) flushTimes.get(new Integer(scope));
        }
    }

    /**
    * Retrieve an item from the cache
    *
    * @param scope The cache scope
    * @param request The servlet request
    * @param key The key of the object to retrieve
    * @param refreshPeriod The time interval specifying if an entry needs refresh
    * @return The requested object
    * @throws NeedsRefreshException
    */
    public Object getFromCache(int scope, HttpServletRequest request, String key, int refreshPeriod) throws NeedsRefreshException {
        Cache cache = getCache(request, scope);
        key = this.generateEntryKey(key, request, scope);
        return cache.getFromCache(key, refreshPeriod);
    }

    /**
    * Checks if the given scope was flushed more recently than the CacheEntry provided.
    * Used to determine whether to refresh the particular CacheEntry.
    *
    * @param cacheEntry The cache entry which we're seeing whether to refresh
    * @param scope The scope we're checking
    *
    * @return Whether or not the scope has been flushed more recently than this cache entry was updated.
    */
    public boolean isScopeFlushed(CacheEntry cacheEntry, int scope) {
        Date flushDateTime = getFlushTime(scope);

        if (flushDateTime != null) {
            long lastUpdate = cacheEntry.getLastUpdate();
            return (flushDateTime.getTime() >= lastUpdate);
        } else {
            return false;
        }