From 6798e01f492773305ec89030628d684156b84b80 Mon Sep 17 00:00:00 2001
From: Benjamin Gamard <b.gamard@sismics.com>
Date: Thu, 5 Apr 2018 19:19:22 +0200
Subject: [PATCH] Closes #224: scan for indexing handler

---
 .../sismics/docs/core/model/context/AppContext.java | 13 +++++++++++--
 .../docs/core/util/indexing/IndexingHandler.java    |  7 +++++++
 .../core/util/indexing/LuceneIndexingHandler.java   |  8 ++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/docs-core/src/main/java/com/sismics/docs/core/model/context/AppContext.java b/docs-core/src/main/java/com/sismics/docs/core/model/context/AppContext.java
index fcd42a1c..c340ad62 100644
--- a/docs-core/src/main/java/com/sismics/docs/core/model/context/AppContext.java
+++ b/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());
diff --git a/docs-core/src/main/java/com/sismics/docs/core/util/indexing/IndexingHandler.java b/docs-core/src/main/java/com/sismics/docs/core/util/indexing/IndexingHandler.java
index 563676f7..459caa6c 100644
--- a/docs-core/src/main/java/com/sismics/docs/core/util/indexing/IndexingHandler.java
+++ b/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.
      *
diff --git a/docs-core/src/main/java/com/sismics/docs/core/util/indexing/LuceneIndexingHandler.java b/docs-core/src/main/java/com/sismics/docs/core/util/indexing/LuceneIndexingHandler.java
index a9285318..c753fb62 100644
--- a/docs-core/src/main/java/com/sismics/docs/core/util/indexing/LuceneIndexingHandler.java
+++ b/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();