java - Why is this JPA 2.0 entity merged only after a find()? -

my application creates object in first transaction. then, transaction tries update database changes, instead of updating entity, new 1 created. if find before merge, right record updated. why that?

this entity:

@entity public class myobject implements serializable{      @id     @generatedvalue(strategy = generationtype.sequence, generator = "my_seq")     @sequencegenerator(name = "my_seq", sequencename = "my_seq_gen", allocationsize = 1)     long id;      string stuff;     string businesskey;      // getter, setters, hashcode, equals (using "businesskey") } 

this record created , updated: (see below create , update):

myobject obj = bean.create(); bean.update(obj); 

but said before, fails update first record, creates 1 instead!

if try find entity before merge operation (without doing returned object), it's correctly updated (see below create , findandupdate):

myobject obj = bean.create(); bean.findandupdate(obj); 

here ejb:

@transactionattribute(transactionattributetype.requires_new) @stateless public class bean {  final static logger logger = loggerfactory.getlogger(bean.class);  @persistencecontext(unitname = "myunit") entitymanager em;  public myobject create(){      myobject obj = new myobject();     obj.businesskey = "some string";      em.persist(obj);      logger.debug("myobject.id: {}", obj.id); // eg. 100      return obj; }  public void update(myobject obj){      obj.stuff = "some stuff";      myobject merged = em.merge(obj);      logger.debug("obj.id: {}", obj.id); // still 100     logger.debug("merged.id: {}", merged.id); // new id: 101!  }  public void findandupdate(myobject obj){      obj.stuff = "some stuff";      em.find(myobject.class, obj.id); // doing nothing returned myobject      myobject merged = em.merge(obj);      logger.debug("obj.id: {}", obj.id); // still 100     logger.debug("merged.id: {}", merged.id); // still 100!  } } 

the problem seems outside given code. guessing myobject instance passing on update() created either calling new or through sort of deserialization, json example. entity manager instance em (usually created @ request start , destroyed after it's end) contains entities have been loaded it. these entities compared reference when looked-up , not tested key equality. in essence, using contains, asking "are tracking instance of object?", , can have many instances of object of same class same primary key, entity manager not track them unless received reference it.