jsf - Retrieve the id of an Entity object as soon as the entity was instantiated? -

is there way in jpa retrieve id of entity object entity instantiated? e.g person person = new person();

currently using in entity class following strategy: @generatedvalue(strategy = generationtype.identity)

if not there "dummy id" strategy having dummyid e.g -10 etc before actual primary key set table in database? please note primary key in mysql db set autoincrement.

the reason need able add new entities in lists , sort them using there id in jsf datatables before persisting them in db.

there no way retrieve id before persisting - because has no id until persist entity. has nothing strategy. has concurrence.

but can add own temporary key use case:

@entity public class person {     private static final atomiclong counter = new atomiclong();      @id     @generatedvalue(strategy = generationtype.identity)     private long id;      private final transient long tempid = counter.decrementandget();      public long getidforcomparison() {         return id == null ? tempid : id;     }  } 

remember counter decrease every created object - instantiated jpa provider. if count new (unpersisted) objects, or worried time of atomic counter, should use different constructor jpa:

@entity public class person {     private static final atomiclong counter = new atomiclong();      @id     @generatedvalue(strategy = generationtype.identity)     private long id;      private transient long tempid;      private string name;      protected person() {         // constructor jpa - nothing do, id attached     }      public person(string name) {         // constructor creation of new objects         tempid = counter.decrementandget();         this.name = name;     }      public long getidforcomparison() {         return id == null ? tempid : id;     }  }