BatchProcessor is fed work by a BatchProcessWorkProvider

- Avoids necessity to supply full or clever Collection


git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@20752 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/batch/BatchProcessWorkProvider.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2005-2010 Alfresco Software Limited.
+ *
+ * This file is part of Alfresco
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.alfresco.repo.batch;
+
+import java.util.Collection;
+
+/**
+ * An interface that provides work loads to the {@link BatchProcessor}.
+ * 
+ * @author Derek Hulley
+ * @since 3.4
+ */
+public interface BatchProcessWorkProvider<T>
+{
+    /**
+     * Get an estimate of the total number of objects that will be provided by this instance.
+     * Instances can provide accurate answers on each call, but only if the answer can be
+     * provided quickly and efficiently; usually it is enough to to cache the result after
+     * providing an initial estimate.
+     * 
+     * @return                  a total work size estimate
+     */
+    int getTotalEstimatedWorkSize();
+    
+    /**
+     * Get the next lot of work for the batch processor.  Implementations should return
+     * the largest number of entries possible; the {@link BatchProcessor} will keep calling
+     * this method until it has enough work for the individual worker threads to process
+     * or until the work load is empty.
+     * 
+     * @return                  the next set of work object to process or an empty collection
+     *                          if there is no more work remaining.
+     */
+    Collection<T> getNextWork();
+}