--- a/src/main/java/de/mpiwg/gazetteer/utils/DBService.java	Fri May 19 20:12:34 2017 +0200
+++ b/src/main/java/de/mpiwg/gazetteer/utils/DBService.java	Wed Jun 21 05:56:02 2017 +0200
@@ -15,6 +15,7 @@
 import org.apache.log4j.Logger;
 import org.hibernate.Query;
 import org.hibernate.Session;
+import org.hibernate.Transaction;
 
 import de.mpiwg.gazetteer.bo.DBEntry;
 import de.mpiwg.gazetteer.bo.LGBranch;
@@ -854,18 +855,34 @@
 		logger.info("Deleting Branch by branchId=" + branchId);
 
 		int modifiedFiles;
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+
+		try{
+
+			  tx = session.beginTransaction();
+
+				Query query = session.createQuery("delete LGBranch where id = :id");
+				query.setLong("id", branchId);
+				modifiedFiles = query.executeUpdate();
 
-		Query query = session.createQuery("delete LGBranch where id = :id");
-		query.setLong("id", branchId);
-		modifiedFiles = query.executeUpdate();
+				Query query0 = session.createQuery("delete LGFile where branchId = :branchId");
+				query0.setLong("branchId", branchId);
+				modifiedFiles += query0.executeUpdate();
+
+				tx.commit();
+
+		}catch (Exception e) {
 
-		Query query0 = session.createQuery("delete LGFile where branchId = :branchId");
-		query0.setLong("branchId", branchId);
-		modifiedFiles += query0.executeUpdate();
+			 if (tx!=null) tx.rollback();
+
+			 e.printStackTrace();
 
-		session.getTransaction().commit();
+			 throw e;
+
+		}finally {
+			 session.close();
+		}
 
 		return modifiedFiles;
 	}
@@ -873,14 +890,27 @@
 	protected static int deleteFullTextSearchFileFromDB(Long fileId){
 		int modifiedFiles = 0;
 
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+
+		try{
+
+			  tx = session.beginTransaction();
+
+				Query query0 = session.createQuery("delete LGFullTextSearchFile where id = :fileId");
+				query0.setLong("fileId", fileId);
+				modifiedFiles = query0.executeUpdate();
 
-		Query query0 = session.createQuery("delete LGFullTextSearchFile where id = :fileId");
-		query0.setLong("fileId", fileId);
-		modifiedFiles = query0.executeUpdate();
+				tx.commit();
+		}catch (Exception e) {
+				if (tx!=null) tx.rollback();
 
-		session.getTransaction().commit();
+				e.printStackTrace();
+
+				throw e;
+		}finally {
+			session.close();
+		}
 
 		return modifiedFiles;
 	}
@@ -888,15 +918,25 @@
 	protected static int deleteFileFromDB(Long fileId){
 
 		int modifiedFiles;
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+    try{
+         tx = session.beginTransaction();
 
+					Query query0 = session.createQuery("delete LGFile where id = :fileId");
+					query0.setLong("fileId", fileId);
+					modifiedFiles = query0.executeUpdate();
 
-		Query query0 = session.createQuery("delete LGFile where id = :fileId");
-		query0.setLong("fileId", fileId);
-		modifiedFiles = query0.executeUpdate();
+					tx.commit();
+			}catch (Exception e) {
+					if (tx!=null) tx.rollback();
 
-		session.getTransaction().commit();
+					e.printStackTrace();
+
+					throw e;
+			}finally {
+				session.close();
+			}
 
 		return modifiedFiles;
 
@@ -1038,12 +1078,23 @@
 
 	protected static void saveDBEntry(DBEntry entry, Date date){
 
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+    try{
+         tx = session.beginTransaction();
+
+				 saveDBEntry0(session, entry, date);
 
-		saveDBEntry0(session, entry, date);
+				tx.commit();
+		}catch (Exception e) {
+				if (tx!=null) tx.rollback();
 
-		session.getTransaction().commit();
+				e.printStackTrace();
+
+				throw e;
+		}finally {
+			session.close();
+		}
 	}
 
 	public static void saveDBEntry0(Session session, DBEntry entry, Date date){
@@ -1146,35 +1197,6 @@
 	}
 
 
-	// remove it
-	/*
-	public static LGFullTextSearchFile getExistFullTextSearchFile(Long userId, String fileName) {
-		//logger.info("getExistFullTextSearchFile: (userId,fileName)=" + userId + ","+fileName);
-		List<LGFullTextSearchFile> list = new ArrayList<LGFullTextSearchFile>();
-
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
-		Query query = session.createQuery("from LGFullTextSearchFile where userId = :userId and fileName = :fileName");
-		query.setLong("userId", userId);
-		query.setString("fileName", fileName);
-
-		list = query.list();
-		session.getTransaction().commit();
-
-		if (list.size() != 0) {
-			//logger.info("existing record.");
-			return list.get(0);
-		} else {
-			//logger.info("new record.");
-			return null;
-		}
-
-	}
-	 */
-
-
-
-
 	/* --- topic --- */
 	protected static List<LGTopic> getAllLGTopicFromDB(){
 		List<LGTopic> list = null;
@@ -1203,31 +1225,42 @@
 	}
 
 	protected static int deleteTopicFromDB(Long topicId){
+
 		logger.info("Deleting topic by topicId=" + topicId);
 
 		int modifiedTopic;
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
 
-		session.getTransaction().begin();
+		Session session = HibernateUtil.getSessionFactory().openSession();
 
-		// delete record in Topic table
-		Query query = session.createQuery("delete LGTopic where id = :id");
-		query.setLong("id", topicId);
-		modifiedTopic = query.executeUpdate();
+		Transaction tx = null;
+		try{
+				 tx = session.beginTransaction();
+				// delete record in Topic table
+				Query query = session.createQuery("delete LGTopic where id = :id");
+				query.setLong("id", topicId);
+				modifiedTopic = query.executeUpdate();
 
 
-		// delete records in TopicSectionRelation table
-		Query query0 = session.createQuery("delete LGTopicSectionRelation where topicId = :topicId");
-		query0.setLong("topicId", topicId);
-		modifiedTopic += query0.executeUpdate();
+				// delete records in TopicSectionRelation table
+				Query query0 = session.createQuery("delete LGTopicSectionRelation where topicId = :topicId");
+				query0.setLong("topicId", topicId);
+				modifiedTopic += query0.executeUpdate();
+
+				// delete records in TopicTagRelation table
+				Query query1 = session.createQuery("delete LGTopicTagRelation where topicId = :topicId");
+				query1.setLong("topicId", topicId);
+				modifiedTopic += query1.executeUpdate();
 
-		// delete records in TopicTagRelation table
-		Query query1 = session.createQuery("delete LGTopicTagRelation where topicId = :topicId");
-		query1.setLong("topicId", topicId);
-		modifiedTopic += query1.executeUpdate();
+				tx.commit();
+		}catch (Exception e) {
+				if (tx!=null) tx.rollback();
 
+				e.printStackTrace();
 
-		session.getTransaction().commit();
+				throw e;
+		}finally {
+			session.close();
+		}
 
 		return modifiedTopic;
 	}
@@ -1263,15 +1296,26 @@
 	protected static int deleteTopicSectionRelationFromDB(Long relationId){
 
 		int modifiedRelation;
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+    try{
+         tx = session.beginTransaction();
 
 
-		Query query0 = session.createQuery("delete LGTopicSectionRelation where id = :relationId");
-		query0.setLong("relationId", relationId);
-		modifiedRelation = query0.executeUpdate();
+				Query query0 = session.createQuery("delete LGTopicSectionRelation where id = :relationId");
+				query0.setLong("relationId", relationId);
+				modifiedRelation = query0.executeUpdate();
 
-		session.getTransaction().commit();
+				tx.commit();
+		}catch (Exception e) {
+				if (tx!=null) tx.rollback();
+
+				e.printStackTrace();
+
+				throw e;
+		}finally {
+			session.close();
+		}
 
 		return modifiedRelation;
 

--- a/src/main/java/de/mpiwg/gazetteer/utils/DataProvider.java	Fri May 19 20:12:34 2017 +0200
+++ b/src/main/java/de/mpiwg/gazetteer/utils/DataProvider.java	Wed Jun 21 05:56:02 2017 +0200
@@ -9,6 +9,7 @@
 
 import org.apache.log4j.Logger;
 import org.hibernate.Session;
+import org.hibernate.Transaction;
 
 import cl.maps.duplex.DuplexKey;
 import de.mpiwg.gazetteer.bo.LGBranch;
@@ -24,39 +25,39 @@
 import de.mpiwg.gazetteer.utils.exceptions.VersioningException;
 
 public class DataProvider extends AbstractDataProvider{
-	
+
 	private static Logger logger = Logger.getLogger(DataProvider.class);
 	private static DataProvider instance;
-	
+
 	public static DataProvider getInstance(){
 		if(instance == null)
 			instance = new DataProvider();
 		return instance;
 	}
-	
+
 	public static void resetInstance() {
 		instance = null;
 	}
-	
+
 	public DataProvider(){
 		logger.info("##### Starting DataProvider #####");
 	}
-	
-	
+
+
 
 	/* --- branch --- */
-	
+
 	public LGFile getFile(Long fileId){
 		return getFileMap().getValuesByOwnKey(fileId);
 	}
-	
+
 	public List<LGFile> getAllFiles(Long branchId){
 		List<LGFile> list = getFileMap().getValuesByAKey(branchId);
 		Collections.sort(list);
 		Collections.reverse(list);
 		return list;
 	}
-	
+
 	public List<LGTopicSectionRelation> getAllExistingTopicSectionRelation() {
 		List<LGTopicSectionRelation> list = new ArrayList<LGTopicSectionRelation>();
 		for (LGTopicSectionRelation relation : getTopicSectionRelationMap().values()) {
@@ -64,15 +65,15 @@
 		}
 		return list;
 	}
-	
+
 	public List<LGBranch> getAllExistingBranches(){
 		List<LGBranch> list = new ArrayList<LGBranch>();
-		for(LGBranch branch : getBranchMap().values()){	
+		for(LGBranch branch : getBranchMap().values()){
 			list.add(branch);
 		}
 		return list;
 	}
-	
+
 	public List<LGBranch> getBranches(Long userId){
 		List<LGBranch> list = new ArrayList<LGBranch>();
 		for(LGBranch branch : getBranchMap().values()){
@@ -82,49 +83,49 @@
 		}
 		return list;
 	}
-	
-	
+
+
 	public LGBranch getBranch(Long branchId){
 		return getBranchMap().getValuesByOwnKey(branchId);
 	}
-	
+
 	public void deleteFile(LGFile file) throws Exception{
-	
+
 		LGBranch branch = getBranch(file.getBranchId());
-		
+
 		if(branch == null){
 			throw new Exception("There is any Branch for " + file);
 		}
-		
+
 		List<LGFile> files = getAllFiles(file.getBranchId());
-		
+
 		if(files.size() == 1){
 			throw new Exception("This file could not be deleted, because it is part of a branch that has only one file. A Branch without files is a inconsistency.");
 		}
-		
+
 		// if the file is the last version of a branch, we must replace the current file with the penultimate file.
 		if(branch.getCurrentLastFileId().equals(file.getId())){
 			LGFile penultimateFile = getPenultimateFile(files);
-			
+
 			penultimateFile.setLastVersion(true);
 			branch.setCurrentLastFileId(penultimateFile.getId());
-			
+
 			this.updateBranch(branch);
 			this.updateFile(penultimateFile);
-			
+
 		}
-		
+
 		//deleting file from DB and cache
 		int modifiedFiles = DBService.deleteFileFromDB(file.getId());
 		getFileMap().remove(file.getKey());
-		
+
 		logger.info(modifiedFiles + " items deleted by removing file " + file);
 	}
-	
+
 	private LGFile getPenultimateFile(List<LGFile> files){
 		LGFile penultimateFile = null;
 		LGFile lastFile = null;
-		
+
 		for(LGFile file : files){
 			if(lastFile == null){
 				lastFile = file;
@@ -140,15 +141,15 @@
 				}
 			}
 		}
-		
+
 		return penultimateFile;
 	}
-	
+
 	public void deleteBranch(LGBranch branch){
-		
+
 		int modifiedFiles = DBService.deleteBranchFromDB(branch.getId());
 		List<LGFile> fileToDelete = getFileMap().getValuesByAKey(branch.getId());
-		
+
 		for(LGFile file : new ArrayList<LGFile>(fileToDelete)){
 			getFileMap().remove(file.getKey());
 		}
@@ -156,198 +157,234 @@
 
 		logger.info(modifiedFiles + " items deleted by removing branch " + branch.toString());
 	}
-	
+
 	public void updateFile(LGFile file) throws Exception{
 		if(!file.isPersistent()){
 			throw new Exception("Trying to update a file that it is not persistent!");
 		}
-		
+
 		Date date = new Date();
 		DBService.saveDBEntry(file, date);
 		this.getFileMap().put(file.getKey(), file);
 	}
-	
+
 	public void updateBranch(LGBranch branch) throws Exception{
 		if(!branch.isPersistent()){
 			throw new Exception("Trying to update a branch that it is not persistent!");
 		}
-		
+
 		Date date = new Date();
 		DBService.saveDBEntry(branch, date);
 		this.getBranchMap().put(branch.getKey(), branch);
 	}
-	
+
 	public LGFile saveFile(Long branchId, String text, Long userId, Long userPreviousFileId) throws Exception{
-		
-		
-		
+
 		Date date = new Date();
-		
+
 		LGBranch branch = getBranchMap().getValuesByOwnKey(branchId);
-		
+
 		if(!branch.hasContributor(userId)){
 			throw new NoAuthorizedException(userId, branchId);
 		}
-		
+
 		if(!branch.getCurrentLastFileId().equals(userPreviousFileId)){
 			LGFile userPreviousFile = getFileMap().getValuesByOwnKey(userPreviousFileId);
 			LGFile currentLastFile = getFileMap().getValuesByOwnKey(branch.getCurrentLastFileId());
-			
+
 			throw new VersioningException(userPreviousFile, currentLastFile);
 		}
-		
+
 		LGFile previousFile = getFileMap().getValuesByOwnKey(branch.getCurrentLastFileId());
-		
+
 		LGFile file = new LGFile();
 		file.setBranchId(branchId);
 		file.setVersion(previousFile.getVersion() + 1);
 		file.setUserId(userId);
 		file.setContent(text);
-		
+
 		//Saving into DB
 		//##################################
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
-		
-		
-		file.setBranchId(branch.getId());
-		DBService.saveDBEntry0(session, file, date);
-		
-		previousFile.setLastVersion(false);
-		DBService.saveDBEntry0(session, previousFile, date);
-		
-		branch.setCurrentLastFileId(file.getId());
-		DBService.saveDBEntry0(session, branch, date);
-		
-		//Saving physical file in the operating system
-		String fileName = FileManager.saveFile(branch, file, date, userId);
-		file.setFileName(fileName);
-		DBService.saveDBEntry0(session, file, date);
-		
-		session.getTransaction().commit();
-		//##################################
-		
-		
-		//Saving into Cache
-		getBranchMap().put(branch.getKey(), branch);
-		getFileMap().put(file.getKey(), file);
-		getFileMap().put(previousFile.getKey(), previousFile);
-		
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+
+		try{
+
+			  tx = session.beginTransaction();
+
+				file.setBranchId(branch.getId());
+				DBService.saveDBEntry0(session, file, date);
+
+				previousFile.setLastVersion(false);
+				DBService.saveDBEntry0(session, previousFile, date);
+
+				branch.setCurrentLastFileId(file.getId());
+				DBService.saveDBEntry0(session, branch, date);
+
+				//Saving physical file in the operating system
+				String fileName = FileManager.saveFile(branch, file, date, userId);
+				file.setFileName(fileName);
+
+		    DBService.saveDBEntry0(session, file, date);
+
+		    tx.commit();
+
+				//##################################
+
+				//Saving into Cache
+				getBranchMap().put(branch.getKey(), branch);
+				getFileMap().put(file.getKey(), file);
+				getFileMap().put(previousFile.getKey(), previousFile);
+
+		}catch (Exception e) {
+
+			 if (tx!=null) tx.rollback();
+
+			 e.printStackTrace();
+
+			 throw e;
+
+		}finally {
+			 session.close();
+		}
+
 		return file;
 	}
-	
+
 	public Long saveNewFile(String text, String label, Long sectionId, Long userId) throws Exception{
-		
+
 		Date date = new Date();
-		
-		LGBranch branch = new LGBranch();				
+
+		LGBranch branch = new LGBranch();
 		branch.setSectionId(sectionId);
 		branch.setUserId(userId);
 		branch.setLabel(label);
 		branch.addContributor(userId);
 		branch.loadTransientData();
-		
+
 		LGFile file = new LGFile();
 		file.setUserId(userId);
 		file.setContent(text);
-		
+
 		//Saving into DB
 		//##################################
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
-		
-		DBService.saveDBEntry0(session, branch, date);
-		file.setBranchId(branch.getId());
-		
-		DBService.saveDBEntry0(session, file, date);
-		branch.setCurrentLastFileId(file.getId());
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+    try{
+         tx = session.beginTransaction();
+
+					DBService.saveDBEntry0(session, branch, date);
+					file.setBranchId(branch.getId());
+
+					DBService.saveDBEntry0(session, file, date);
+					branch.setCurrentLastFileId(file.getId());
+
+					//Saving physical file in the operating system
+					String fileName = FileManager.saveFile(branch, file, date, userId);
+					file.setFileName(fileName);
+					DBService.saveDBEntry0(session, file, date);
+
+					tx.commit();
 
-		//Saving physical file in the operating system
-		String fileName = FileManager.saveFile(branch, file, date, userId);
-		file.setFileName(fileName);
-		DBService.saveDBEntry0(session, file, date);
-		
-		session.getTransaction().commit();
+					//Saving into Cache
+					getBranchMap().put(branch.getKey(), branch);
+					getFileMap().put(file.getKey(), file);
+
+    }catch (Exception e) {
+       if (tx!=null) tx.rollback();
+
+			 e.printStackTrace();
+
+       throw e;
+    }finally {
+       session.close();
+    }
 		//##################################
-		
-		
-		//Saving into Cache
-		getBranchMap().put(branch.getKey(), branch);
-		getFileMap().put(file.getKey(), file);
-		
+
 		return branch.getId();
-		
+
 	}
 
 	/* --- end branch --- */
-	
-	
-	
+
+
+
 	/* --- full text search --- */
-	
+
 	public List<LGFullTextSearchFile> getSearchFileList4User(Long userId) {
-	
+
 		List<LGFullTextSearchFile> list = new ArrayList<LGFullTextSearchFile>();
-		
+
 		for(LGFullTextSearchFile searchFile : getFullTextSearchFileMap().values()){
 			if(searchFile.getUserId() == userId){
 				list.add(searchFile);
 			}
 		}
-		
+
 		return list;
 	}
 
-	
-	
-	
+
+
+
 	public void deleteLGFullTextSearchFile(LGFullTextSearchFile file) throws IOException{
 		//deleting file from DB: the record in table FullTextSearchFile
 		int modifiedFiles = DBService.deleteFullTextSearchFileFromDB(file.getId());
-		
-		// delete the files from file system (html in ftsearch-data/... and csv in LGMap/datasets/) 
+
+		// delete the files from file system (html in ftsearch-data/... and csv in LGMap/datasets/)
 		FileManager.deleteFullTextSearchFileCsv(file);
 		FileManager.deleteFullTextSearchFileHtml(file);
-		
+
 		// delete file from cache
 		this.getFullTextSearchFileMap().remove(file.getKey());
 		logger.debug("deleteLGFullTextSearchFile");
 	}
-	
-	public LGFullTextSearchFile saveLGFullTextSearchFile(List<DBContents> list, Long userId, LGFullTextSearchFile searchFile) throws Exception {	
+
+	public LGFullTextSearchFile saveLGFullTextSearchFile(List<DBContents> list, Long userId, LGFullTextSearchFile searchFile) throws Exception {
 		// save as csv and html file in filesystem, and records in db `FullTextSearchFile
 		// List<DBContents> list is the filteredList of searching result with isRemoved field
-	
+
 		Date date = new Date();
-		
+
 		//Saving into DB
 		//##################################
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
-		
-		DBService.saveDBEntry0(session, searchFile, date);
-		
-		//Saving physical file in the operating system
-		FileManager.saveFullTextSearchFileAsCsv(searchFile, userId, list);	// save csv file to LGMap's datasets folder
-		FileManager.saveFullTextSearchFileAsHtml(searchFile, userId, list);	// save html file to LGMap's datasets folder
-		
-		session.getTransaction().commit();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+    try{
+         tx = session.beginTransaction();
+
+		     DBService.saveDBEntry0(session, searchFile, date);
+
+				 //Saving physical file in the operating system
+				 FileManager.saveFullTextSearchFileAsCsv(searchFile, userId, list);	// save csv file to LGMap's datasets folder
+				 FileManager.saveFullTextSearchFileAsHtml(searchFile, userId, list);	// save html file to LGMap's datasets folder
+
+				 tx.commit();
+		}catch (Exception e) {
+         if (tx!=null) tx.rollback();
+
+				 e.printStackTrace();
+
+         throw e;
+    }finally {
+       session.close();
+    }
 		//##################################
-		
+
 		return searchFile;
 	}
 
 	public LGFullTextSearchFile getFullTextSearchFile(Long fileId) {
 
 		LGFullTextSearchFile file = getFullTextSearchFileMap().getValuesByOwnKey(fileId);
-		
+
 		return file;
 	}
 
 	/* --- end full text search --- */
 
 	/* --- topic --- */
-	
+
 	public List<LGTopic> getTopics(Long userId){
 		List<LGTopic> list = new ArrayList<LGTopic>();
 		for(LGTopic topic : getTopicMap().values()){
@@ -356,33 +393,34 @@
 				list.add(topic);
 			}
 			*/
-			
+
 			// add topic into list anyway, without checking the contributor role.
 			list.add(topic);
 		}
-		
+
 		return list;
 	}
-	
+
 	public LGTopic getTopic(Long topicId){
 		return getTopicMap().getValuesByOwnKey(topicId);
 	}
-	
-	
+
+
 	public void deleteTopic(LGTopic topic){
-			
+
 		int modifiedRelation = DBService.deleteTopicFromDB(topic.getId());
 		getTopicMap().remove(topic.getKey());
-		
+
 		logger.info("removing " + modifiedRelation + " records in TopicSectionRelation and TopicTagRelation table for the topic " + topic.toString());
-		
+
 		this.setTopicSectionRelationMap(null);	// clear topicSectionRelationMap cache
-		
+
 	}
 
 	public void createTopic(String nameEn, String nameCh,String namePinyin, String description, Long userId) {
+
 		Date date = new Date();
-		
+
 		LGTopic topic = new LGTopic();
 		topic.setNameEn(nameEn);
 		topic.setNameCh(nameCh);
@@ -390,80 +428,89 @@
 		topic.setDescription(description);
 		topic.setUserId(userId);
 		topic.setContributors("[" + userId.toString() + "]");
-		
+
 		// auto-generating a tag for the topic: could be from nameEn replace space with '_'
 		String tag = new String();
 		tag = nameEn.replace(' ', '_');
 		topic.setTag(tag);
-		
+
 		//Saving into DB
 		//##################################
 		// For Topic table
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
-		
-		DBService.saveDBEntry0(session, topic, date);
-			
-		// For Taglist table
-		// create record, which is the topic tag, in taglist table,
-		// with the taglis.name=nameCh, the taglist.tag=tag, the taglist.color=the defualt topic tag color, which is rgb(255,0,174)
-		
-		LGTaglist taglist = new LGTaglist();
-		taglist.setName(nameCh);
-		
-		// tag to lowercase only!! bcuz it will be used as topic tag in Extraction-interface, and it'll be a tag in HTML which is case-insensitive
-		taglist.setTag(tag.toLowerCase());
-		
-		taglist.setColor("rgb(255, 0, 174)");
-		
-		DBService.saveDBEntry0(session, taglist, date);
-		
-		
-		logger.debug("new topic tag id=" + taglist.getId());
-		
-		
-		// For TopicTagRelation table
-		// link the relation between the new topic and its corresponding tag
-		LGTopicTagRelation relation = new LGTopicTagRelation();
-		relation.setTagId(taglist.getId());
-		relation.setTopicId(topic.getId());
-		
-		DBService.saveDBEntry0(session, relation, date);
-		
-		
-		session.getTransaction().commit();
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+		try{
+				tx = session.beginTransaction();
+
+				DBService.saveDBEntry0(session, topic, date);
+
+				// For Taglist table
+				// create record, which is the topic tag, in taglist table,
+				// with the taglis.name=nameCh, the taglist.tag=tag, the taglist.color=the defualt topic tag color, which is rgb(255,0,174)
+
+				LGTaglist taglist = new LGTaglist();
+				taglist.setName(nameCh);
+
+				// tag to lowercase only!! bcuz it will be used as topic tag in Extraction-interface, and it'll be a tag in HTML which is case-insensitive
+				taglist.setTag(tag.toLowerCase());
+
+				taglist.setColor("rgb(255, 0, 174)");
+
+				DBService.saveDBEntry0(session, taglist, date);
+
+		    logger.debug("new topic tag id=" + taglist.getId());
+
+				// For TopicTagRelation table
+				// link the relation between the new topic and its corresponding tag
+				LGTopicTagRelation relation = new LGTopicTagRelation();
+				relation.setTagId(taglist.getId());
+				relation.setTopicId(topic.getId());
+
+				DBService.saveDBEntry0(session, relation, date);
+
+				tx.commit();
+
+    }catch (Exception e) {
+       if (tx!=null) tx.rollback();
+
+			 e.printStackTrace();
+
+       throw e;
+    }finally {
+       session.close();
+    };
 		//##################################
-		
+
 	}
 
 	public void updateTopic(LGTopic topic) throws Exception {
 		if(!topic.isPersistent()){
 			throw new Exception("Trying to update a topic that it is not persistent!");
 		}
-		
+
 		Date date = new Date();
 		DBService.saveDBEntry(topic, date);
 		this.getTopicMap().put(topic.getKey(), topic);
-		
+
 	}
-	
-	
-	
+
+
+
 	public List<DBSection> getAllSectionsInTopic(Long topicId) throws SQLException{
-		
+
 		List<LGTopicSectionRelation> topicSectionRelationList = getTopicSectionRelationMap().getValuesByAKey(topicId);
 
 		// get sections from topicSecionRelation list
 		List<DBSection> list = new ArrayList<DBSection>();
 		for (LGTopicSectionRelation aRelation : topicSectionRelationList) {
 			//logger.debug(aRelation.getInfo() );
-			
+
 			DBSection section = DBService.getSectionWithContent(aRelation.getSectionId());
 			list.add(section);
-			
+
 		}
-		
-		
+
+
 		Collections.sort(list);
 		Collections.reverse(list);
 		return list;
@@ -475,32 +522,32 @@
 	public void deleteTopicSectionRelation(Long topicId, String bookId) throws Exception{
 		// delete record with topicId, bookId in topicSectionRelation
 		// this means the sectionId = 0, there is no corresponding section in the book for this topic
-		
+
 		// TODO
-		
+
 	}
 
 	public void deleteTopicSectionRelation(Long topicId, Long sectionId) throws Exception{
 		if (sectionId == 0) {
 			throw new Exception("sectionId cannot be 0");
 		}
-		
+
 		DuplexKey<Long, Long> key = new DuplexKey<Long, Long>(topicId, sectionId);
 		LGTopicSectionRelation topicSectionRelation = this.getTopicSectionRelationMap().get(key);
 
 		LGTopic topic = getTopic(topicId);
-		
+
 		if(topic == null){
 			throw new Exception("There is no topic of " + topicSectionRelation);
 		}
-		
+
 		//deleting topicSectionRelation from DB and cache
 		int modifiedRelation = DBService.deleteTopicSectionRelationFromDB(topicSectionRelation.getId());
 		getTopicSectionRelationMap().remove(topicSectionRelation.getKey());
-		
+
 		logger.info(modifiedRelation + " items deleted by removing topicSectionRelation " + topicSectionRelation.toString());
 
-		
+
 	}
 
 	public String updateTopicSectionRelation(Long sectionId, Long topicId) throws Exception {
@@ -510,56 +557,62 @@
 		if (topicSectionRelation != null) {
 			// the relation already existed
 			// would this possibly need any modification to the existing record in the topicSectionRelation table?
-			
+
 			return "updated";
-			
+
 		} else {
 			createTopicSectionRelation(sectionId, topicId);
 
 			return "added";
 		}
-		
-	
-		
+
+
+
 	}
-	
-	
+
+
 	public void createTopicSectionRelation(Long sectionId, Long topicId) throws Exception {
-		
+
 		Date date = new Date();
-		
+
 		LGTopicSectionRelation topicSectionRelation = new LGTopicSectionRelation();
 		topicSectionRelation.setTopicId(topicId);
 		topicSectionRelation.setSectionId(sectionId);
-		
+
 		DBService.getInstance();
 		DBSection section = DBService.getSectionWithContent(sectionId);
 		topicSectionRelation.setBookId(section.getBookId());
-		
+
 		//Saving into DB
 		//##################################
 		// For Topic table
-		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
-		session.getTransaction().begin();
-		
-		DBService.saveDBEntry0(session, topicSectionRelation, date);
-			
-		session.getTransaction().commit();
-		//##################################
-		
+		Session session = HibernateUtil.getSessionFactory().openSession();
+		Transaction tx = null;
+    try{
+       tx = session.beginTransaction();
+       DBService.saveDBEntry0(session, topicSectionRelation, date);
+       tx.commit();
+    }catch (Exception e) {
+       if (tx!=null) tx.rollback();
+       e.printStackTrace();
+			 throw e;
+    }finally {
+       session.close();
+    }
+
 		// update cache
 		this.loadTopicSectionRelations();
-	
+
 	}
 
 	public Integer getNumberOfSectionInTopic(Long topicId) {
 		List<LGTopicSectionRelation> topicSectionRelationList = getTopicSectionRelationMap().getValuesByAKey(topicId);
-	
+
 		return topicSectionRelationList.size();
 	}
 
-	
-	
+
+
 	/* --- end topic --- */
-	
+
 }