Moving to root below branch label

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@2005 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/content/metadata/MetadataExtracterRegistry.java

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+/*
+ * Copyright (C) 2005 Jesper Steen M<>ller
+ *
+ * Licensed under the Mozilla Public License version 1.1 
+ * with a permitted attribution clause. You may obtain a
+ * copy of the License at
+ *
+ *   http://www.alfresco.org/legal/license.txt
+ *
+ * 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.alfresco.repo.content.metadata;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+import org.alfresco.error.AlfrescoRuntimeException;
+import org.alfresco.repo.content.MimetypeMap;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.util.Assert;
+
+/**
+ * Holds and provides the most appropriate metadate extracter for a particular
+ * mimetype.
+ * <p>
+ * The extracters themselves know how well they are able to extract metadata.
+ * 
+ * @see org.alfresco.repo.content.metadata.MetadataExtracter
+ * @author Jesper Steen M<>ller
+ */
+public class MetadataExtracterRegistry
+{
+    private static final Log logger = LogFactory.getLog(MetadataExtracterRegistry.class);
+
+    private List<MetadataExtracter> extracters;
+    private Map<String, MetadataExtracter> extracterCache;
+
+    private MimetypeMap mimetypeMap;
+    /** Controls read access to the cache */
+    private Lock extracterCacheReadLock;
+    /** controls write access to the cache */
+    private Lock extracterCacheWriteLock;
+
+    /**
+     * @param mimetypeMap all the mimetypes available to the system
+     */
+    public MetadataExtracterRegistry(MimetypeMap mimetypeMap)
+    {
+        Assert.notNull(mimetypeMap, "The MimetypeMap is mandatory");
+        this.mimetypeMap = mimetypeMap;
+
+        extracters = Collections.emptyList(); // just in case it isn't set
+        extracterCache = new HashMap<String, MetadataExtracter>(17);
+
+        // create lock objects for access to the cache
+        ReadWriteLock extractionCacheLock = new ReentrantReadWriteLock();
+        extracterCacheReadLock = extractionCacheLock.readLock();
+        extracterCacheWriteLock = extractionCacheLock.writeLock();
+    }
+
+    /**
+     * Gets the best metadata extracter. This is a combination of the most
+     * reliable and the most performant extracter.
+     * <p>
+     * The result is cached for quicker access next time.
+     * 
+     * @param mimetype the source MIME of the extraction
+     * @return Returns a metadata extracter that can extract metadata from the
+     *         chosen MIME type.
+     */
+    public MetadataExtracter getExtracter(String sourceMimetype)
+    {
+        // check that the mimetypes are valid
+        if (!mimetypeMap.getMimetypes().contains(sourceMimetype))
+        {
+            throw new AlfrescoRuntimeException("Unknown extraction source mimetype: " + sourceMimetype);
+        }
+
+        MetadataExtracter extracter = null;
+        extracterCacheReadLock.lock();
+        try
+        {
+            if (extracterCache.containsKey(sourceMimetype))
+            {
+                // the translation has been requested before
+                // it might have been null
+                return extracterCache.get(sourceMimetype);
+            }
+        }
+        finally
+        {
+            extracterCacheReadLock.unlock();
+        }
+
+        // the translation has not been requested before
+        // get a write lock on the cache
+        // no double check done as it is not an expensive task
+        extracterCacheWriteLock.lock();
+        try
+        {
+            // find the most suitable transformer - may be empty list
+            extracter = findBestExtracter(sourceMimetype);
+            // store the result even if it is null
+            extracterCache.put(sourceMimetype, extracter);
+            return extracter;
+        }
+        finally
+        {
+            extracterCacheWriteLock.unlock();
+        }
+    }
+
+    /**
+     * @param sourceMimetype The MIME type under examination
+     * @return The fastest of the most reliable extracters in
+     *         <code>extracters</code> for the given MIME type.
+     */
+    private MetadataExtracter findBestExtracter(String sourceMimetype)
+    {
+        double bestReliability = -1;
+        long bestTime = Long.MAX_VALUE;
+        logger.debug("Finding best extracter for " + sourceMimetype);
+
+        MetadataExtracter bestExtracter = null;
+
+        for (MetadataExtracter ext : extracters)
+        {
+            double r = ext.getReliability(sourceMimetype);
+            if (r == bestReliability)
+            {
+                long time = ext.getExtractionTime();
+                if (time < bestTime)
+                {
+                    bestExtracter = ext;
+                    bestTime = time;
+                }
+            }
+            else if (r > bestReliability)
+            {
+                bestExtracter = ext;
+                bestReliability = r;
+                bestTime = ext.getExtractionTime();
+            }
+        }
+        return bestExtracter;
+    }
+
+    /**
+     * Provides a list of self-discovering extracters.
+     * 
+     * @param transformers all the available extracters that the registry can
+     *        work with
+     */
+    public void setExtracters(List<MetadataExtracter> extracters)
+    {
+        logger.debug("Setting " + extracters.size() + "new extracters.");
+
+        extracterCacheWriteLock.lock();
+        try
+        {
+            this.extracters = extracters;
+            this.extracterCache.clear();
+        }
+        finally
+        {
+            extracterCacheWriteLock.unlock();
+        }
+    }
+}