问题描述
我有两个表具有多对多关系.当我坚持用户不插入任何东西来联接表时，我映射了这两个实体.我一直在调试，直到坚持，我看到组列表不为空.
I have two table with many-to-many relations. I mapped this two entities when I am persisting users doesn't insert anything to join table. I am debugging till the persist, I see groups list is not null.
没有错误消息，只是坚持用户.
Ther is no error message just persist user.
用户<->用户组<->组
users <--> user-group <--> groups
我正在使用netbeans 7.3，Glassfish 3.1.2.2，postgresql 9.1和eclipselink 2
I am using netbeans 7.3, Glassfish 3.1.2.2, postgresql 9.1 and eclipselink 2
此外，我试图显示下面的属性对我不起作用的sql脚本.
Also, I tried to show sql scripts that properties below doesn't work for me.
<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"/>
摘要AAO:
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
网上论坛实体
@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;
}
}
推荐答案
您需要启用cascade进行合并(使用PERSIST)或使用ALL进行的所有操作.
You need to enable cascade for merge (using PERSIST) or all operations with ALL.
@ManyToMany(mappedBy = "usersList", cascade = CascadeType.PERSIST)
private List<Groups> groupsList;
映射/联接表的工作方式是user_group在user和group表上具有外键约束.这就是为什么必须在group中插入新行作为其主键的原因，以便将新行添加到user_group.
The way a mapping/join table works is that user_group would have a foreign key constraint on user and group table. That's why a new row in group has to be inserted for its primary key to be used to add a new row to user_group.
这与JPA无关，即使您使用的是普通JDBC，这也同样适用于您.这是实体关系在数据库中的工作方式.
This has nothing to do with JPA and the same would apply to you even if you were using plain JDBC instead. This is how Entity-Relationships work in database.
此行为由为您的persistence-unit指定的eclipselink.ddl-generation属性控制.当指定为drop-and-create-tables时，EclipseLink将重新创建整个数据库模式(删除进程中的任何现有数据).
This behaviour is controlled by the eclipselink.ddl-generation property specified for your persistence-unit. When specified as drop-and-create-tables, EclipseLink recreates the whole database schema (deleting any existing data in the process).
<property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
但是，启用此功能只是为了简化您的开发.不应在通过不指定此属性或将其值设置为none禁用该功能的生产环境中使用此功能.
This, however, is enabled just to ease your development. This isn't supposed to be used in production environments where its disabled by not specifying this property or by setting its value as none.
<property name="eclipselink.ddl-generation" value="none"/>
这篇关于JPA多对多坚持加入表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！