Closes #224: scan for indexing handler

docs-core/src/main/java/com/sismics/docs/core/model/context/AppContext.java

@@ -1,5 +1,6 @@
 package com.sismics.docs.core.model.context;
 
+import com.google.common.collect.Lists;
 import com.google.common.eventbus.AsyncEventBus;
 import com.google.common.eventbus.EventBus;
 import com.sismics.docs.core.constant.Constants;
@@ -11,7 +12,7 @@ import com.sismics.docs.core.service.FileService;
 import com.sismics.docs.core.service.InboxService;
 import com.sismics.docs.core.util.PdfUtil;
 import com.sismics.docs.core.util.indexing.IndexingHandler;
-import com.sismics.docs.core.util.indexing.LuceneIndexingHandler;
+import com.sismics.util.ClasspathScanner;
 import com.sismics.util.EnvironmentUtil;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -76,8 +77,16 @@ public class AppContext {
         resetEventBus();
 
         // Start indexing handler
-        indexingHandler = new LuceneIndexingHandler();
         try {
+            List<Class<? extends IndexingHandler>> indexingHandlerList = Lists.newArrayList(
+                    new ClasspathScanner<IndexingHandler>().findClasses(IndexingHandler.class, "com.sismics.docs.core.util.indexing"));
+            for (Class<? extends IndexingHandler> handlerClass : indexingHandlerList) {
+                IndexingHandler handler = handlerClass.newInstance();
+                if (handler.accept()) {
+                    indexingHandler = handler;
+                    break;
+                }
+            }
             indexingHandler.startUp();
         } catch (Exception e) {
             log.error("Error starting the indexing handler, rebuilding the index: " + e.getMessage());

docs-core/src/main/java/com/sismics/docs/core/util/indexing/IndexingHandler.java

@@ -16,6 +16,13 @@ import java.util.List;
  * @author bgamard
  */
 public interface IndexingHandler {
+    /**
+     * Return true if this indexing handler can start.
+     *
+     * @return True if able to start
+     */
+    boolean accept();
+
     /**
      * Start the indexing handler.
      *

docs-core/src/main/java/com/sismics/docs/core/util/indexing/LuceneIndexingHandler.java

@@ -16,6 +16,7 @@ import com.sismics.docs.core.util.jpa.PaginatedList;
 import com.sismics.docs.core.util.jpa.PaginatedLists;
 import com.sismics.docs.core.util.jpa.QueryParam;
 import com.sismics.docs.core.util.jpa.SortCriteria;
+import com.sismics.util.ClasspathScanner;
 import org.apache.lucene.analysis.standard.StandardAnalyzer;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.StringField;
@@ -44,6 +45,7 @@ import java.util.*;
  *
  * @author bgamard
  */
+@ClasspathScanner.Priority(100)
 public class LuceneIndexingHandler implements IndexingHandler {
     /**
      * Logger.
@@ -60,6 +62,12 @@ public class LuceneIndexingHandler implements IndexingHandler {
      */
     private DirectoryReader directoryReader;
 
+    @Override
+    public boolean accept() {
+        // Embedded Lucene can always start
+        return true;
+    }
+
     @Override
     public void startUp() throws Exception {
         ConfigDao configDao = new ConfigDao();