Question

我正在尝试使用Map with Hibernate创建一个简单的程序。我有一个国家实体，其中包含州的地图。这是我的课程：

@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
}

这是我创建一些国家和州的程序：

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();
        }
    }

当我尝试运行此程序时，我得到例外：

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]

我在第session.save(country);行收到此异常请告诉我为什么会收到此错误？

更新

根据JB给出的答案，现在我将@GeneratedValue添加到我在国家和州的ID中。这次我开始异常：

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

以下是Hibernate生成的DDL和DML操作：

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=?

我不清楚我还在哪里。

Answer 1

您的州实体的ID不是自动生成的。而且您始终创建状态而不指定任何ID。所以你所有的州都有相同的ID：0因此异常。

Hibernate Map抛出 - ORA-01722：无效的数字错误

1 个答案: