EntityManager标识符生成异常？

我试图通过entitybean和entitymanager在数据库中创建记录时遇到了这个问题。我在UserManagerImpl.java两种方法，奇怪的是在findalluser方法效果很好，并创建一个动作JBoss的7台以下异常：代码下面给出EntityManager标识符生成异常？

identifier generation excepton: ids for this class must be manully assigned before calling save(): gmartinc.swe645.common.entitybeans.user

我使用的SQL语句在MySQL中创建表是

create table users(
userid varchar(100) primary key, 
firstname varchar(100), 
lastname varchar(100), 
group varchar(100), 
team varchar(100) 
); 

and the Entitybean to map this table is 

    import java.io.Serializable; 
import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.Id; 
import javax.persistence.Table; 


@Entity 
@Table(name = "users") 
public class user implements Serializable { 
    private String userid; 
    private String firstname; 
    private String lastname; 
    private String password; 
    private String team; 


    @Id 
    @Column(name="userid") 
    public String getUserId() { 
    return userid; 
    } 
    public void setUserId(String id) { 
    this.userid = id; 
    } 

    @Column(name="firstname") 
    public String getFirstName() { 
    return firstname; 
    } 
    public void setFirstName(String firstName) { 
    this.firstname = firstName; 
    } 

    @Column(name = "lastname") 
    public String getLastName() { 
    return lastname; 
    } 
    public void setLastName(String lastName) { 
    this.lastname = lastName; 
    } 

    @Column(name = "password") 
    public String getPassWord() { 
    return password; 
    } 
    public void setPassWord(String password) { 
    this.password = password; 
    } 

    @Column(name = "team") 
    public String getTeam() { 
    return team; 
    } 
    public void setTeam(String team) { 
    this.team = team; 
    } 


} 

and the UserManagerImpl.java is 
import java.util.List; 

import javax.ejb.Stateless; 
import javax.ejb.Stateful; 
import javax.persistence.EntityManager; 
import javax.persistence.PersistenceContext; 
import javax.persistence.Query; 


@Stateless 
public class UserManagerImpl implements UserManagerRemote { 
    @PersistenceContext(unitName = "Swe645University") 
    private EntityManager entityManager; 

    public void createUser(user us) { 
    entityManager.persist(us); 
    } 

    public List<user> findUser() { 
     Query q = entityManager.createQuery(" from user p "); 
     return q.getResultList(); 
     } 
}

真不知道什么是错的，在此先感谢！

来源

2011-11-05 user899628

您需要为您的ID指定一个生成器。

如果您的基础持久性管理器是hibernate，请查看hibernate生成器。

来源

2011-11-05 07:59:03 dcernahoschi

但如果我添加@Generator我得到超时，所以这意味着我的表必须是序列表？那么创建序列表的正确语法是什么？ – user899628

EntityManager标识符生成异常？

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