ID of object with all of its variables in hibernate -

with class, want class's id value of of attributes. implicitly means need row these values existing in database. how in hibernate?

public class weatherstate {     private string weathertype;     private double temperature; } 

when persistent attributes should directly attributes of weatherstate, @idclass way go (persistence annotations imported javax.persistence package):

@entity @idclass(weatherstateid.class) public class weatherstate {     @id private string weathertype;     @id private double temperature;     //getters, setters }  public class weatherstateid implements serializable {     private string weathertype;     private double temperature;     //getters, setters, equals, hashcode } 

other options use @embeddedid:

@entity public class weatherstate {     @embeddedid private weatherstateid weatherstateid;      public weatherstateid getweatherstateid() {         return weatherstateid;     }      public void setweatherstateid(weatherstateid weatherstateid) {         this.weatherstateid = weatherstateid;     } }  @embeddable public class weatherstateid implements serializable {     private string weathertype;     private double temperature;     //getters, setters, equals, hashcode } 

in both cases important provide equals , hashcode, said in jpa 2.0 specification:

the primary key class must define equals , hashcode methods. semantics of value equality these methods must consistent database equality database types key mapped.