Class CachedResource

java/org/apache/catalina/webresources/CachedResource.java:51–701

This class is designed to wrap a 'raw' WebResource and providing caching for expensive operations. Inexpensive operations may be passed through to the underlying resource.

 * operations may be passed through to the underlying resource.
 */
public class CachedResource implements WebResource {

    private static final Log log = LogFactory.getLog(CachedResource.class);
    private static final StringManager sm = StringManager.getManager(CachedResource.class);

    // Estimate (on high side to be safe) of average size excluding content
    // based on profiler data.
    private static final long CACHE_ENTRY_SIZE = 500;

    private final Cache cache;
    private final StandardRoot root;
    private final String webAppPath;
    private final long ttl;
    private final int objectMaxSizeBytes;
    private final boolean usesClassLoaderResources;

    private volatile WebResource webResource;
    private volatile WebResource[] webResources;
    private volatile long nextCheck;

    private volatile Long cachedLastModified = null;
    private volatile String cachedLastModifiedHttp = null;
    private volatile byte[] cachedContent = null;
    private volatile Boolean cachedIsFile = null;
    private volatile Boolean cachedIsDirectory = null;
    private volatile Boolean cachedExists = null;
    private volatile Boolean cachedIsVirtual = null;
    private volatile Long cachedContentLength = null;
    private volatile String cachedStrongETag = null;


    /**
     * Construct a cached resource.
     *
     * @param cache The cache
     * @param root The standard root
     * @param path The web application path
     * @param ttl The time to live in milliseconds
     * @param objectMaxSizeBytes The maximum size of objects to cache
     * @param usesClassLoaderResources Whether class loader resources are used
     */
    public CachedResource(Cache cache, StandardRoot root, String path, long ttl, int objectMaxSizeBytes,
            boolean usesClassLoaderResources) {
        this.cache = cache;
        this.root = root;
        this.webAppPath = path;
        this.ttl = ttl;
        nextCheck = ttl + System.currentTimeMillis();
        this.objectMaxSizeBytes = objectMaxSizeBytes;
        this.usesClassLoaderResources = usesClassLoaderResources;
    }

    /**
     * Validates the cached resource.
     *
     * @param useClassLoaderResources Whether class loader resources are used
     *
     * @return <code>true</code> if the cached resource is still valid