休眠多对一的外键注释映射

Question

我在Spring 3.1中使用了Hibernate 4，并且从这个映射中生成的外键约束有问题。

@Entity 
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) 
public abstract class O { 
    private String oid; 

    @Id 
    @GeneratedValue(generator = "OidGenerator") 
    @GenericGenerator(name = "OidGenerator", strategy = "com.evolveum.midpoint.repo.sql.OidGenerator") 
    @Column(unique = true, nullable = false, updatable = false, length = 36) 
    public String getOid() { 
     return oid; 
    } 
    ...other getters and setters 
} 

@Entity 
public class Role extends O { 
    private Set<Assignment> assignments; 

    @OneToMany(mappedBy = "owner") 
    @Cascade({org.hibernate.annotations.CascadeType.ALL}) 
    public Set<Assignment> getAssignments() { 
     return assignments; 
    } 
    ...other getters and setters 
} 

@Entity 
public class User extends O { 
    private Set<Assignment> assignments; 

    @OneToMany(mappedBy = "owner") 
    @Cascade({org.hibernate.annotations.CascadeType.ALL}) 
    public Set<Assignment> getAssignments() { 
     return assignments; 
    } 
    ...other getters and setters 
} 

@Entity 
public class Assignment extends IdentifiableContainer { 
    private O owner; 
    private Long id; 

    @Id 
    @MapsId("oid") 
    @ManyToOne 
    public O getOwner() { 
     return owner; 
    } 

    @Id 
    @GeneratedValue(generator = "ContainerIdGenerator") 
    @GenericGenerator(name = "ContainerIdGenerator", strategy = "com.evolveum.midpoint.repo.sql.ContainerIdGenerator") 
    @Column(nullable = true, updatable = true) 
    public Long getId() { 
     return id; 
    } 
...other getters and setters 
} 

这将产生模式是这样的...

create table Assignment (
    id bigint not null, 
    owner_oid varchar(36) not null,  
    primary key (owner_oid, id) 
); 
create table Role (
    oid varchar(36) not null unique, 
    primary key (oid) 
); 
create table User (
    oid varchar(36) not null unique, 
    primary key (oid) 
); 
alter table Assignment 
    add constraint FKB3FD62ED72781986 
    foreign key (owner_oid) 
    references User; 
alter table Assignment 
    add constraint FKB3FD62ED7276AE31 
    foreign key (owner_oid) 
    references Role; 

上Assignment.owner_oid两个约束不应该存在。因为他们，我无法保存角色/用户的任务。我想到了使用连接表的其他解决方案，但我看起来过于尴尬。加入表看起来像

create table Role_Assignment (
    role_oid varchar(36) ... 
    assignment_oid varchar(36) ... 
    assignment_id bigint ... 
    primary key (....) 
); 

但我因此在这种连接表前两colums是始终不变的assignment.owner_oid注解为@MapsId。此外，我还有更多类从O.class扩展，这意味着许多连接表。如何禁用赋值表上的FK约束？

Answer 1

你应该将

... 
public Set<Assignment> getAssignments() { 
    return assignments; 
} 

抽象类，它在这两个类是相同的。

为了回答你的问题 - 做完这些之后，你可以将你的InheritanceType改为JOINED（或SINGLE_TABLE，但你说你有很多其他的子类，因此它不合适） - 那么你将只有一个拥有owner_oid列的表应该从转让中引用。