java - Hibernate updating Null Values to dynamic updatable table -

here problem facing.

i have table not-null field create_date. dont want update particular column when update done in table. gave

dynamic-insert="true" dynamic-update="true" 

in table hbm.xml. problem getting error trying update null not-null field though not modifying object. pasting code here.

if (userdo.getuserid() != null) {                 if(sessionmanager.getinstance().currentsession() != null){                     getsession().evict(userdo);                     getsession().clear();                 }                 getsession().update(userdo);                 //getsession().saveorupdate(userdo);              }  

in domain class above field don't want store null set:

@column (nullable = false)