java - Hibernate @OneToMany 不保存外键

Question

我在保存一对多关系时遇到问题。看起来它是将列表的元素保存在表中，但没有将外键保存在正确的表中。

@Entity
@Table(name = "tbl_applications")
public class ApplicationEntity
{
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "intAPI", referencedColumnName = "intCode")
    private ApiResourceEntity objApi;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "strApplication")
    List<ApplicationRoleEntity> colApplicationRoles = new ArrayList<ApplicationRoleEntity>();
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "strApplication")
    List<URLEntity> colUrls = new ArrayList<URLEntity>();
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "strApplication")
    List<KeyCredentialEntity> colKeyCredentials = new ArrayList<KeyCredentialEntity>();
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "strApplication")
    List<PasswordCredentialEntity> colPasswordCredentials = new ArrayList<PasswordCredentialEntity>();
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "strApplication")
    List<RequiredResourceAccessEntity> colRequiredResourceAccess = new ArrayList<RequiredResourceAccessEntity>();
}
@Entity
@Table(name = "tbl_apiresources")
public class ApiResourceEntity
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "intCode")
    private Integer intCode;
    private Integer intRequestedAccessTokenVersion;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "intCode")
    private List<PermissionScopeEntity> colOauth2PermissionsScope = new ArrayList<PermissionScopeEntity>();
}
@Entity
@Table(name = "tbl_permissionsscope")
public class PermissionScopeEntity
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "intCode")
    private Integer intCode;
    private String strAdminConsentDescription;
    private String strAdminConsentDisplayName;
    private String strID;
    private Boolean bolIsEnabled;
    private String strOrigin;
    private String strType;
    private String strUserConsentDescription;
    private String strUserConsentDisplayName;
    private String strValue;
}

<小时/>

它在数据库中保存的内容的示例:

tbl_applications
intAPI = 1
tbl_apiresources
intCode = 1
intRequestAccessTokenVersion = 2
intOauth2PermissionScopes = NULL
tbl_permissionsscope
intCode = 1
strAdminConsentDescription = xxxxxx
strAdminConsentDisplayName = xxxxxx
strID = xxxxxx
bolIsEnabled = xxxxxx
strOrigin = xxxxxx
strType = xxxxxx
strUserConsentDescription = xxxxxx
strUserConsentDisplayName = xxxxxx
strValue = xxxxxx

它保存列表的元素(权限范围)，但是外键不保存在表 tbl_apiresources 上。也许是因为标识符是一个身份字段(自行生成)

ApplicationEntity 对象的所有 @OneToMany 关系均已正确保存。 @OneToMany 无法指向 @ManyToOne，因为我收到循环引用异常

Answer 1

当您仅指定@OneToMany时关系，即从父级到子级的单向关系，hibernate将通过连接表实现映射。当您保存父/子关系时，键将插入到连接表中:

@Entity
public class Parent {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
    @OneToMany
    Set<Child> children;
}
@Entity
public class Child {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
}

连接表parent_child中的结果

Hibernate: create sequence hibernate_sequence start with 1 increment by 1
Hibernate: create table child (id bigint not null, primary key (id))
Hibernate: create table parent (id bigint not null, primary key (id))
Hibernate: create table parent_children (parent_id bigint not null, children_id bigint not null, primary key (parent_id, children_id))
Hibernate: alter table parent_children add constraint UK_fh9rqlaf2416b31ec7n92nrfh unique (children_id)
Hibernate: alter table parent_children add constraint FK2li53iimvay1c1bjvc1hed3gl foreign key (children_id) references child
Hibernate: alter table parent_children add constraint FKdnxvj4hlnv40nix37bpjsvecn foreign key (parent_id) references parent
Hibernate: call next value for hibernate_sequence
Hibernate: insert into child (id) values (?)
Hibernate: call next value for hibernate_sequence
Hibernate: insert into parent (id) values (?)
Hibernate: insert into parent_children (parent_id, children_id) values (?, ?)

如果您希望 FK 位于子表中(您确实这样做了)，则定义从子表到父表的单向映射。

@Entity
public class Parent {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
}
@Entity
public class Child {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;   
    @ManyToOne
    Parent parent;
}

这不会创建连接表

Hibernate: create sequence hibernate_sequence start with 1 increment by 1
Hibernate: create table child (id bigint not null, parent_id bigint, primary key (id))
Hibernate: create table parent (id bigint not null, primary key (id))
Hibernate: alter table child add constraint FK7dag1cncltpyhoc2mbwka356h foreign key (parent_id) references parent
Hibernate: call next value for hibernate_sequence
Hibernate: insert into parent (id) values (?)
Hibernate: call next value for hibernate_sequence
Hibernate: insert into child (parent_id, id) values (?, ?)

如果您想要双向映射，则添加两者，但了解您应该像第二个示例一样进行持久化并使用父 Set<Child> children仅用于出于性能原因的查询。

@Entity
public class Parent {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
    @OneToMany
    Set<Child> children;
}
@Entity
public class Child {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;

    @ManyToOne
    Parent parent;
}

插入后，再用left outer join fetch查询或者更好地使用 EntityGraph .

"from Parent p left outer join fetch p.children where p.id = :id"