JPA多对多持续加入表

Question

我有两张表与多对多的关系.当我持久化用户没有插入任何东西来连接表时,我映射了这两个实体.我正在调试直到持久化,我看到组列表不为空.

Ther是没有错误消息只是坚持用户.

用户< - >用户组< - >组

我使用的是netbeans 7.3,Glassfish 3.1.2.2,postgresql 9.1和eclipselink 2

另外,我试图显示下面的属性对我不起作用的sql脚本.

        <property name="eclipselink.logging.logger" value="ServerLogger"/>
        <property name="eclipselink.logging.level" value="FINE"/>
        <property name="eclipselink.logging.level.sql" value="FINE"/>
        <property name="eclipselink.logging.parameters" value="true"/>

Abstact DAO:

public abstract class GenericDAO<E> implements Serializable{

@PersistenceContext
EntityManager entityManager;

public void persist(E object){
    entityManager.persist(object);
}

public void merge(E object){
    entityManager.merge(object);
}

public void delete(E object){
    object = entityManager.merge(object);
    entityManager.remove(object);
}
}

用户实体:

   @Entity
@Table(name = "users")
@XmlRootElement
@NamedQueries(
{
    @NamedQuery(name = "Users.findAll", query = "SELECT u FROM Users u"),
    @NamedQuery(name = "Users.findByUserId", query = "SELECT u FROM Users u WHERE u.userId = :userId"),
    @NamedQuery(name = "Users.findByName", query = "SELECT u FROM Users u WHERE u.name = :name"),
    @NamedQuery(name = "Users.findBySurname", query = "SELECT u FROM Users u WHERE u.surname = :surname"),
    @NamedQuery(name = "Users.findByEmail", query = "SELECT u FROM Users u WHERE u.email = :email"),
    @NamedQuery(name = "Users.findByUsername", query = "SELECT u FROM Users u WHERE u.username = :username"),
    @NamedQuery(name = "Users.findByPassword", query = "SELECT u FROM Users u WHERE u.password = :password")
})
public class Users implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "user_id")
    private Integer userId;
    @Size(max = 2147483647)
    @Column(name = "name")
    private String name;
    @Size(max = 2147483647)
    @Column(name = "surname")
    private String surname;
    // @Pattern(regexp="[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?", message="Invalid email")//if the field contains email address consider using this annotation to enforce field validation
    @Size(max = 2147483647)
    @Column(name = "email")
    private String email;
    @Size(max = 2147483647)
    @Column(name = "username")
    private String username;
    @Size(max = 2147483647)
    @Column(name = "password")
    private String password;
    @ManyToMany(mappedBy = "usersList")
    private List<Groups> groupsList;
    @OneToMany(mappedBy = "userId")
    private List<Person> personList;

//Getters Setters

团体实体:

@Entity
@Table(name = "groups")
@XmlRootElement
@NamedQueries(
{
    @NamedQuery(name = "Groups.findAll", query = "SELECT g FROM Groups g"),
    @NamedQuery(name = "Groups.findByGroupId", query = "SELECT g FROM Groups g WHERE g.groupId = :groupId"),
    @NamedQuery(name = "Groups.findByGroupName", query = "SELECT g FROM Groups g WHERE g.groupName = :groupName"),
    @NamedQuery(name = "Groups.findByGroupDescription", query = "SELECT g FROM Groups g WHERE g.groupDescription = :groupDescription")
})
public class Groups implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "group_id")
    private Integer groupId;
    @Size(max = 2147483647)
    @Column(name = "group_name")
    private String groupName;
    @Size(max = 2147483647)
    @Column(name = "group_description")
    private String groupDescription;
    @JoinTable(name = "user_group", joinColumns =
    {
        @JoinColumn(name = "group_id", referencedColumnName = "group_id")
    }, inverseJoinColumns =
    {
        @JoinColumn(name = "user_id", referencedColumnName = "user_id")
    })
    @ManyToMany(fetch = FetchType.EAGER)
    private List<Users> usersList;
//Getters Setters

用户DAO:

public class UserDAO extends GenericDAO<Users> implements Serializable {

    public List<Users> getAllUsers()
    {
        Query query = entityManager.createNamedQuery("Users.findAll");
        List<Users> users = query.getResultList();
        return users;
    }
}

Answer 1

您需要启用cascade合并(使用PERSIST)或所有操作ALL.

@ManyToMany(mappedBy = "usersList", cascade = CascadeType.PERSIST)
private List<Groups> groupsList;

如果我设置CascadeType.PERSIST,它也会将数据插入到组表中.我想添加日期用户表和user_group表(pk_user,pk_group)

映射/连接表的工作方式是在table 和table 上user_group有外键约束.这就是为什么必须为其主键插入新行以用于添加新行的原因.usergroupgroupuser_group

这与JPA无关,即使您使用的是普通的JDBC,它也适用于您.这就是实体关系在数据库中的工作方式.

我也删除了所有表,它们是由eclipse链接自动生成的.它们相同但不向'user_group'插入任何行.

此行为由eclipselink.ddl-generation为您指定的属性控制persistence-unit.当指定为drop-and-create-tables,EclipseLink重新创建整个数据库模式(删除过程中的任何现有数据).

<property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>

但是,这只是为了简化您的开发.通过不指定此属性或将其值设置为禁用,禁止在禁用它的生产环境中使用它none.

<property name="eclipselink.ddl-generation" value="none"/>