休眠多對一的外鍵註釋映射

Question

我在Spring 3.1中使用了Hibernate 4，並且從這個映射中生成的外鍵約束有問題。

@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 
} 

這將產生模式是這樣的...

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兩個約束不應該存在。因爲他們，我無法保存角色/用戶的任務。我想到了使用連接表的其他解決方案，但我看起來過於尷尬。加入表看起來像

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

但我因此在這種連接表前兩colums是始終不變的assignment.owner_oid註解爲@MapsId。此外，我還有更多類從O.class擴展，這意味着許多連接表。如何禁用賦值表上的FK約束？

Answer 1

你應該將

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

抽象類，它在這兩個類是相同的。

爲了回答你的問題 - 做完這些之後，你可以將你的InheritanceType改爲JOINED（或SINGLE_TABLE，但你說你有很多其他的子類，因此它不合適） - 那麼你將只有一個擁有owner_oid列的表應該從轉讓中引用。