Question

我需要支持涉及以下实体（使用JPA）的方案：

用户
帐户
角色

一个用户可以有多个帐户，并且一个帐户可以在多个用户之间共享，这是到目前为止的标准@ManyToMany关系。

每个帐户的用户可以拥有一组不同的角色，一个角色可以在多个用户之间共享。

我遵循了this practice，它解释了一种映射带有多列的多对多关联的方法，但我不确定我是否理解。

用户实体：

@Entity
@Table(name = "users")
public class User implements Serializable {

    @Id
    @Column(name = "id", unique = true, nullable = false)
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "org.hibernate.id.UUIDGenerator")
    private String id;

    @Column(name = "email", nullable = false)
    private String email;

    @Column(name = "full_name", nullable = false)
    private String fullName;

    @OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<UserAccount> usersAccounts;

    public User() {
        usersAccounts= Sets.newHashSet();
    }

    public User(String email, String fullName) {
        this();
        this.email = email;
        this.fullName = fullName;
    }



    public void addAccont(Account account) {
        UserAccount userAccount = new UserAccount(this, account);
        accounts.add(userAccount);
        account.getUsers().add(userAccount);
        this.accounts.add(userAccount);
    }

    public void removeAccont(Account account) {
        for (Iterator<UserAccount> iterator = accounts.iterator(); iterator.hasNext(); ) {
            UserAccount userAccount = iterator.next();

            if (userAccount.getUser().equals(this) &&
                    userAccount.getAccount().equals(account)) {
                iterator.remove();
                userAccount.getAccount().getUsers().remove(userAccount);
                userAccount.setUser(null);
                userAccount.setAccount(null);
            }
        }
    }

    //Getters  Setters..

}

帐户实体：

@Entity
@Table(name = "accounts")
public class Account implements Serializable {

    @Id
    @Column(name = "id", unique = true, nullable = false)
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "org.hibernate.id.UUIDGenerator")
    private String id;

    @Column(name = "name", nullable = false)
    private String name;

    @Column(name = "billing_address", nullable = false)
    private String billingAddress;

    @OneToMany(mappedBy = "account", cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<UserAccount> usersAccounts;


    public Account() {
        usersAccounts= Sets.newHashSet();
    }

    //Getters  Setters..
}

UserAccount实体：

@Entity
@Table(name = "users_accounts")
public class UserAccount implements Serializable {

    @EmbeddedId
    private UserAccountId id;

    @ManyToOne(
        fetch = FetchType.LAZY,
        cascade = {
                CascadeType.PERSIST,
                CascadeType.MERGE
        })
    private User user;

    @ManyToOne(
        fetch = FetchType.LAZY,
        cascade = {
                CascadeType.PERSIST,
                CascadeType.MERGE
        })
    private Account account;

    @ManyToMany(
        fetch = FetchType.LAZY,
        cascade = {
                CascadeType.PERSIST,
                CascadeType.MERGE
        })
    @JoinTable(
        name = "users_accounts_roles",
        joinColumns = {
                @JoinColumn(name = "user_id", referencedColumnName = "user_id"),
                @JoinColumn(name = "account_id", referencedColumnName = "account_id"),
        },
        inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName = "id")
)
private Set<Role> roles;


    private UserAccount() {}

    public UserAccount(@NotNull User user, @NotNull Account account) {
        this.user = user;
        this.account = account;
        roles = Sets.newHashSet();
        this.id = new UserAccountId(user.getId(), account.getId());
    }

    //Getters  Setters..

}

UserAccountId：

@Embeddable
public class UserAccountId implements Serializable {

    @Column(name = "user_id")
    private String userId;

    @Column(name = "account_id")
    private String accountId;

    private UserAccountId() {
    }

    public UserAccountId(
            String userId,
            String accountId) {
        this.userId = userId;
        this.accountId = accountId;
    }

    //Getters  Setters..
}

我正在创建一个新用户，并尝试将其保存到数据库：

User user = new User("some.email@mail.com", "John Doe");
userRepository.save(savedEntity);

我收到JpaSystemException：

Caused by: java.sql.SQLException: Field 'user_account_account_id' doesn't have a default value

我看过hibernate的create table语句：

create table users
(
  id                      varchar(255) not null
    primary key,
  email                   varchar(255) not null,
  full_name               varchar(255) not null,
  user_account_account_id varchar(255) not null,
  user_account_user_id    varchar(255) not null,
  constraint UK_exxyrhm7e34pwn8dvem8wxuxu
  unique (user_account_account_id, user_account_user_id),
  constraint FKhti2663qxk7qo15f7gfnnaj7r
  foreign key (user_account_account_id, user_account_user_id) references users_accounts (account_id, user_id)
)
  engine = InnoDB;

我不清楚标记为user_account_account_id的{{1}}和user_account_user_id列，据我了解，在我的实体中，无需帐户即可创建用户。< / p>

为什么以这种方式创建表？我该如何运作？

Answer 1

这是正确的吗？

您的解决方案将起作用，只是听起来很复杂。您确定多对多关联不应该在Role和Account之间（而不是UserAccount之间）吗？换句话说，Account会根据使用哪个Roles而具有不同的User？

此外，我在您建议的映射中发现了一个问题。您可能想要：

@JoinTable(
            name = "users_accounts_roles",
            joinColumns = {
                @JoinColumn(name = "user_id", referencedColumnName = "user_id"),
                @JoinColumn(name = "account_id", referencedColumnName = "account_id"),
            },
            inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName = "id")
    )

（因为id中没有要引用的UserAccount列；而是有两个主键列）

Answer 2

我的感觉是user_account_account_id和user_account_user_id列都是您先前尝试的遗留物。您可以安全地删除它们，然后一切正常。

为了安全起见，您可以完全删除“用户”表，然后从头开始重新创建它。

JPA ManyToMany具有额外的ManyToMany关系

2 个答案: