java - 如何持久化 EnumSet(使用两个数据库表)？

Question

我想在我的实体中将一组选项表示为 EnumSet，并在我的数据库中表示为一对多关系。这是如何正确完成的？我只能找到旧的(预注释)答案或不使用两个表的答案。

我定义了以下表格:

CREATE TABLE Users (
    id                      SERIAL PRIMARY KEY,
    name                    VARCHAR(255) NOT NULL UNIQUE
);

CREATE TABLE User_Options (
    user_id                 INT,
    user_option             VARCHAR(255),
    PRIMARY KEY (user_id, user_option),
    FOREIGN KEY (user_id) REFERENCES Users(id)
                ON DELETE CASCADE
                ON UPDATE CASCADE
);

这个实体类:

@Entity(name = "Users")
public final class User {

    @Id
    @GeneratedValue
    private int id;

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

    private final Set<UserOption> options;

    {
        this.options = EnumSet.noneOf(UserOption.class);
    }

    /* plain getter for id included */

    /* plain getter and setter for name included */

    @ElementCollection(fetch = FetchType.EAGER)
    @Enumerated(EnumType.STRING)
    @CollectionTable(name = "User_Options"
            , joinColumns = @JoinColumn(name = "user_id"))
    @Column(name = "user_option", nullable = false)
    public Set<UserOption> getOptions() {
        return this.options;
    }

}

当然还有枚举:

public enum UserOption {

    OPTION_A,
    OPTION_B,
    OPTION_C;

}

当我启动 Tomcat 时，出现以下异常:

org.hibernate.MappingException: Could not determine type for: java.util.Set, at table: Users, for columns: [org.hibernate.mapping.Column(options)]

这个异常是一堆异常相互引发的根源。它会导致 javax.persistence.PersistenceException(无法构建 EntityManagerFactory)，进而导致一些依赖项注入(inject)异常。

我承认我对 JPA/Hibernate 不够精通，无法理解我做错了什么。谁能帮帮我？

Answer 1

事实证明，答案比我想象的要简单。您不能在实例变量和 getter 上混合使用 JPA 注释。注释本身很好。我按如下方式更改了我的实体类，现在一切正常。

@Entity(name = "Users")
public final class User {

    @Id
    @GeneratedValue
    private int id;

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

    @ElementCollection(fetch = FetchType.EAGER)
    @Enumerated(EnumType.STRING)
    @CollectionTable(name = "User_Options"
            , joinColumns = @JoinColumn(name = "user_id"))
    @Column(name = "user_option", nullable = false)
    private final Set<UserOption> options;

    {
        this.options = EnumSet.noneOf(UserOption.class);
    }

    /* plain getter for id included */

    /* plain getter and setter for name included */

    public Set<UserOption> getOptions() {
        return this.options;
    }

}