Will also check is the strength enough

src/main/java/org/leolo/nrapi/Constants.java

@@ -4,4 +4,6 @@ public class Constants {
     public static final String REQ_ATTR_USER_ID = "auth-result-user-id";
 
     public static final String SESSION_ATTR_USER_ID = "auth-result-user-id";
+
+    public static final int BCRYPT_STRENGTH = 12;
 }

src/main/java/org/leolo/nrapi/web/LoginAPI.java

@@ -31,7 +31,7 @@ public class LoginAPI {
     ){
         String reqIP = HttpReqRespUtils.getClientIpAddressIfServletRequestExist();
         log.info("Login request from {}, username is {}, password length = {}", reqIP, userName, password.length());
-        BCryptPasswordEncoder enc = new BCryptPasswordEncoder();
+        BCryptPasswordEncoder enc = new BCryptPasswordEncoder(Constants.BCRYPT_STRENGTH);
         boolean result = false;
         try(
                 Connection conn = DatabaseManager.getInstance().getConnection();
@@ -45,7 +45,10 @@ public class LoginAPI {
                     if(enc.matches(password, passwordHash)){
                         //Login OK
                         result = true;
-                        if(enc.upgradeEncoding(passwordHash)){
+                        String tokens [] = passwordHash.split("\\$");
+                        if(enc.upgradeEncoding(passwordHash) ||
+                                (Integer.parseInt(tokens[2])<Constants.BCRYPT_STRENGTH)
+                        ){
                             log.info("User {} have old version of hash. Update required.", userName);
                             new Thread(()->{
                                 try(
@@ -55,6 +58,7 @@ public class LoginAPI {
                                     psUpd.setString(1, enc.encode(password));
                                     psUpd.setString(2, userName);
                                     psUpd.executeUpdate();
+                                    connection.commit();
                                 }catch (SQLException e){
                                     log.error(e.getMessage(), e);
                                 }