Hibernate Map抛出 - ORA-01722：无效的数字错误

Question

I am trying to create a simple program using Map with Hibernate. I have a Country entity with a Map of State's. Here are my classes:

@Entity
public class Country implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Column(name = "id")
    @GeneratedValue
    private int id;

    @Column(name = "name")
    private String name;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "country_id")
    @MapKeyColumn(name = "id")
    private Map<String, State> states;
// setters & getters
}



@Entity
@Table(name = "state")
public class State {
    @Id
    @Column(name = "id")
    @GeneratedValue
    private int id;

    @Column(name = "name")
    private String name;
// setters & getters
}

Here is my program that creates some countries and states:

public class AppTest {
    private static final SessionFactory concreteSessionFactory;
        static {
         try {
                concreteSessionFactory = HibernateUtil.getSessionFactory();
          } catch (Throwable ex) {
            throw new ExceptionInInitializerError(ex);
          }
        }
        public static Session getSession()
                throws HibernateException {
            return concreteSessionFactory.openSession();
        }

        public static void main(String... args){
            saveCountries();
            showCountries();
       }

        private static void saveCountries() {
            saveCountry("US", "CA", "Texas");
            saveCountry("UK", "London", "Cambridge");           
        }

        private static void saveCountry(String countryName, String... states) {
            Session session=getSession();
            session.beginTransaction();

            Country country = new Country();
            country.setName(countryName);

            Map<String,State> stateMap = new HashMap<String, State>();
            int count = 0;
            for (String stateName : states) {
                State state = new State();
                state.setName(stateName);
                stateMap.put(stateName+ count++, state);
            }
            country.setStates(stateMap);
            session.save(country);
            session.close();
        }

        private static void showCountries() {
            Session session=getSession();
            session.beginTransaction();
            Country c=(Country)session.get(Country.class, new Integer(1));
            Map<String,State> states = c.getStates();
            Iterator entries = states.entrySet().iterator();
            while (entries.hasNext()) {
                Map.Entry<String,State> entry = (Map.Entry) entries.next();
                String key = entry.getKey();
                State value = (State)entry.getValue();
                System.out.println("Key = " + key + ", Value = " + value.getName());
            }
            session.close();
        }
    }

When I try to run this program then I am getting exception as :

Exception in thread "main" org.hibernate.NonUniqueObjectException: A different object with the same identifier value was already associated with the session : [org.hibernate.examples.State#0]

I am getting this exception at line session.save(country); Please let me know why I am getting this error?

Update:

Based on answer given by JB, now I added @GeneratedValue to my Id's in Country and State. This time I started getting exception as:

Aug 22, 2014 1:44:49 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 1722, SQLState: 42000
Aug 22, 2014 1:44:49 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: ORA-01722: invalid number

Also below are DDL and DML operations that Hibernate has generated:

Hibernate: create table Country (id number(10,0) not null, name varchar2(255 char), primary key (id))
Hibernate: create table state (id number(10,0) not null, name varchar2(255 char), country_id number(10,0), primary key (id))
Hibernate: alter table state add constraint FK_lxoqjm8644epv72af3k3jpalx foreign key (country_id) references Country
Hibernate: create sequence hibernate_sequence
Aug 22, 2014 1:44:49 AM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000230: Schema export complete
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: insert into Country (name, id) values (?, ?)
Hibernate: insert into state (name, id) values (?, ?)
Hibernate: insert into state (name, id) values (?, ?)
Hibernate: update state set country_id=?, id=? where id=?

I am not clear on where I am still missing.

Answer 1

Your State entity has an ID that is not autogenerated. And you always create states without specifying any ID. So all your states have the same ID: 0. Hence the exception.