hibernate - How to restrict other columns data getting updated while updating specific columns of a table -

how restrict columns want update in database table rather updating columns of table?

the following update remarks column

@test     public void updateproject() {         try {             project project = new project();             project.setprojectid(234l);             project.setremarks("from junit");             projectservice.update(project);         } catch (exception e) {             system.out.println("error" + e.getmessage());             e.printstacktrace();         }     } 

when execute above updated other column in table, consequently makes other column values null.

how can resolve issue?

daoimpl code

@override     public void update(project project) {             entitymanager.merge(project);         entitymanager.flush();           } 

update 1 modified code

@test     public void updateproject() {         try {             project project = new project();             project = projectservice.load(234l);                         project.setremarks("from junit");             projectservice.update(project);         } catch (exception e) {             system.out.println("error" + e.getmessage());             e.printstacktrace();         }     } 

in code you're merging new object null fields except remarks object persistent in db. that's not right way: hibernate reference manual:

a straightforward way update state of entity instance find() it, , manipulate directly, while persistence context open: modifying persistent objects

if need modify persistent object, first have load it, edit fields need update , save it.

so, load project entity db , update fields need , save() it. save() isn't necessary hibernate checks object modified , automatically saves it.

@test     public void updateproject() {         try {             // load project entity db using it's id 234l             project.setremarks("from junit");             projectservice.save(project);         } catch (exception e) {             system.out.println("error" + e.getmessage());             e.printstacktrace();         }     } 

here's how load object.

in dao need method load object, example:

@override     public project load(long id) {             return entitymanager.find(project.class, id);     }