Hibernate说'；idRol'；不能为空

我试图保存一个引用了usuari和rol的usuariRol。 我检查Usuari对象和Rol对象是否有它们的id，但是hibernate告诉我idRol不能为null

映射有问题吗

表t_usuariRol

@Entity
@Table(name = "t_usuariRol"
        , uniqueConstraints = @UniqueConstraint(columnNames = {"idUsuari", "idRol"}))

public class UsuariRol implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@ManyToOne
@JoinColumn(name = "idUsuari")
private Usuari usuari;

@ManyToOne
@JoinColumn(name = "idRol")
private Rol rol;

@Entity
@Table(name = "a_rol")
public class Rol implements Serializable {

private static final long serialVersionUID = -1979744578967968079L;

static final String PREFIX = "pia.entity.Rol.";
public static final String findAll = PREFIX + "findAll";
public static final String findById = PREFIX + "findById";

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@Column(length = 45)
private String nom;

public void saveUsuariRol(){
 UsuariRol urol;
 Usuari usuari = usuariMgr.findById(1);
 Rol rol = rolMgr.findById(2);  //rol is not null has id and nom
 urol = new UsuariRol(usuari, rol);
 try {
     usuariRolMgr.save(urol);
 } catch (Exception e) {
     System.out.println("error usuarirol with id");
 }

表a\u rol

@Entity
@Table(name = "t_usuariRol"
        , uniqueConstraints = @UniqueConstraint(columnNames = {"idUsuari", "idRol"}))

public class UsuariRol implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@ManyToOne
@JoinColumn(name = "idUsuari")
private Usuari usuari;

@ManyToOne
@JoinColumn(name = "idRol")
private Rol rol;

@Entity
@Table(name = "a_rol")
public class Rol implements Serializable {

private static final long serialVersionUID = -1979744578967968079L;

static final String PREFIX = "pia.entity.Rol.";
public static final String findAll = PREFIX + "findAll";
public static final String findById = PREFIX + "findById";

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@Column(length = 45)
private String nom;

public void saveUsuariRol(){
 UsuariRol urol;
 Usuari usuari = usuariMgr.findById(1);
 Rol rol = rolMgr.findById(2);  //rol is not null has id and nom
 urol = new UsuariRol(usuari, rol);
 try {
     usuariRolMgr.save(urol);
 } catch (Exception e) {
     System.out.println("error usuarirol with id");
 }

UsuariBean.saveUsuariRol

@Entity
@Table(name = "t_usuariRol"
        , uniqueConstraints = @UniqueConstraint(columnNames = {"idUsuari", "idRol"}))

public class UsuariRol implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@ManyToOne
@JoinColumn(name = "idUsuari")
private Usuari usuari;

@ManyToOne
@JoinColumn(name = "idRol")
private Rol rol;

@Entity
@Table(name = "a_rol")
public class Rol implements Serializable {

private static final long serialVersionUID = -1979744578967968079L;

static final String PREFIX = "pia.entity.Rol.";
public static final String findAll = PREFIX + "findAll";
public static final String findById = PREFIX + "findById";

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

@Column(length = 45)
private String nom;

public void saveUsuariRol(){
 UsuariRol urol;
 Usuari usuari = usuariMgr.findById(1);
 Rol rol = rolMgr.findById(2);  //rol is not null has id and nom
 urol = new UsuariRol(usuari, rol);
 try {
     usuariRolMgr.save(urol);
 } catch (Exception e) {
     System.out.println("error usuarirol with id");
 }

}

错误

Hibernate: 
/* insert UsuariRol / 
insert 
 into
 t_usuariRol
 (idRol, idUsuari, version) 
 values
 (?, ?, ?)
10:25:39,184 WARN  [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (default task-52) SQL Error: 1048, SQLState: 23000
10:25:39,186 ERROR [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (default task-52) Column 'idRol' cannot be null
...
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not execute statement
...
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'idRol' cannot be null

@Stateless
public class RolManager {

    protected Logger logger = Logger.getLogger(getClass().getName());

    @PersistenceContext(unitName = "dbPU")
    protected EntityManager em;

    public Rol findById(int id) {
        return this.em.find(Rol.class, id);
    }

    public List<Rol> all() {
        return this.em.createNamedQuery(Rol.findAll, Rol.class).
                getResultList();
    }

    public Rol save(Rol rol) {
        if (rol.getId() == null) {
            this.em.persist(rol);
            return rol;
        } else {
            return this.em.merge(rol);
        }
    }

    public void delete(int id) {
        try {
            Rol reference = this.em.getReference(Rol.class, id);
            this.em.remove(reference);
        } catch (EntityNotFoundException e) {
            //we want to remove it
            logger.error("Entity not found exeption: ", e);
        }
    }
}

RolManager

Hibernate: 
/* insert UsuariRol / 
insert 
 into
 t_usuariRol
 (idRol, idUsuari, version) 
 values
 (?, ?, ?)
10:25:39,184 WARN  [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (default task-52) SQL Error: 1048, SQLState: 23000
10:25:39,186 ERROR [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] (default task-52) Column 'idRol' cannot be null
...
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not execute statement
...
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'idRol' cannot be null

@Stateless
public class RolManager {

    protected Logger logger = Logger.getLogger(getClass().getName());

    @PersistenceContext(unitName = "dbPU")
    protected EntityManager em;

    public Rol findById(int id) {
        return this.em.find(Rol.class, id);
    }

    public List<Rol> all() {
        return this.em.createNamedQuery(Rol.findAll, Rol.class).
                getResultList();
    }

    public Rol save(Rol rol) {
        if (rol.getId() == null) {
            this.em.persist(rol);
            return rol;
        } else {
            return this.em.merge(rol);
        }
    }

    public void delete(int id) {
        try {
            Rol reference = this.em.getReference(Rol.class, id);
            this.em.remove(reference);
        } catch (EntityNotFoundException e) {
            //we want to remove it
            logger.error("Entity not found exeption: ", e);
        }
    }
}

@无状态
公开课经理{
受保护的记录器=Logger.getLogger（getClass（）.getName（））；
@PersistenceContext（unitName=“dbPU”）
受保护的实体管理器em；
公共Rol findById（内部id）{
返回此.em.find（Rol.class，id）；
}
公共列表全部（）{
返回这个.em.createNamedQuery（Rol.findAll，Rol.class）。
getResultList（）；
}
公共Rol保存（Rol Rol）{
if（rol.getId（）==null）{
这个。em。persist（rol）；
返回rol；
}否则{
返回此.em.merge（rol）；
}
}
公共无效删除（int-id）{
试一试{
Rol reference=this.em.getReference（Rol.class，id）；
本.em.remove（参考）；
}捕获（EntityNotFounde异常）{
//我们想删除它
logger.error（“未找到实体验证：”，e）；
}
}
}

我可以推断出的问题是hibernate的会话无法跟踪您的子对象。从一个会话加载并保存在另一个会话中的实体可能会导致问题

所以为了解决这个问题

启动会话和事务

获取子对象

保存父对象

然后提交

---

对上述所有过程使用相同的会话。

如何

rolMgr.findById（2）是否将此对象返回给您？它是通过hibernate DAO还是其他一些类变量返回的？我添加了类管理器，您可以在其中看到您所要求的内容。UsuariRolManager中的保存方法类似。来自管理器的每个方法都获得em注入。是否该实体没有从entityManager分离对象Rol？。我只是findById和save方法中的open and close entityManager。这通常在不保存依赖对象时发生。这就是为什么建议在保存父实体之前先保存它们。在您的情况下，当数据库中没有
rol
时，如果在
UsuariRol
类中添加级联参数，如
@ManyToOne（cascade=CascadeType.ALL）
on
private rol-rol字段，那么它能解决您的问题吗？这是一个很好的解决方案，但我会继续寻找最佳解决方案