Trying to run the code on Digital Ocean Ubuntu instance. Generated license and set key in objectdb conf file. It gives below exceeds evaluation error when we try to run the code.
 Caused by: com.objectdb.o.UserException: Too many persistable types (>10) - exceeds evaluation limit
 at com.objectdb.o.MSG.d(MSG.java:61) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.MST.UC(MST.java:1090) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.WRA.UC(WRA.java:213) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYS.x(TYS.java:768) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYS.v(TYS.java:592) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYM.ae(TYM.java:531) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYM.ac(TYM.java:467) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYM.ao(TYM.java:788) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYM.at(TYM.java:873) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.TYM.aw(TYM.java:945) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.OBM.bB(OBM.java:371) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.o.OBM.bB(OBM.java:257) ~[objectdb-2.5.4.jar:na]
 at com.objectdb.jpa.EMImpl.persist(EMImpl.java:434) ~[objectdb-2.5.4.jar:na]
 at core.db.objectdb.ObjectDBBaseModel.create(ObjectDBBaseModel.java:78) ~[classes/:na]
 ... 58 common frames omitted  
 2016-12-20 23:07:23,220 - [ERROR] - from application in pool-1-thread-1
 message= Unexpected internal exception, cause= [ObjectDB 2.5.4] Unexpected exception (Error 990)
   Generated by Java HotSpot(TM) 64-Bit Server VM 1.8.0_05 (on Linux 4.4.0-53-generic).
 Please report this error on http://www.objectdb.com/database/issue/new
 com.objectdb.o.InternalException: java.lang.NullPointerException: null
 java.lang.NullPointerException
 at com.objectdb.o.ENT.I(ENT.java:597)
 at com.objectdb.o.OBM.bB(OBM.java:381)
 at com.objectdb.o.OBM.bB(OBM.java:257)
 at com.objectdb.jpa.EMImpl.persist(EMImpl.java:434)  
