java - Hibernate map enum 按属性值

Question

我正在尝试使用 Hibernate 执行以下操作:

当一个对象被保存到数据库时，它被保存为枚举的 name 属性的值。

当从 DB 检索对象时，该对象从数据库中读取字符串，并通过枚举的 name 属性的值实例化枚举。

让我阐述一下。

这是枚举:

public enum Position {

    UNSPECIFIED(1L, "Unspecified"),
    SPECIALIST(2L, "Specialist"),
    NOT_SPECIALIST(3L, "Not Specialist");

    private Long id;
    private String name;

    Position(Long id, String name) {
        this.id = id;
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public static Position from(Long id) {
        for(Position position: values()) {
            if(position.getId().equals(id))
                return position;
        }

        throw new IllegalArgumentException("Cannot get position for ID " + id);
    }

    public static Position from(String name) {
        for(Position position: values()) {
            if(position.getName().toUpperCase().equals(name.toUpperCase()))
                return position;
        }

        throw new IllegalArgumentException("No such position " + name);
    }
}

这是一个使用枚举的类:

@Entity(name = "worker")
public class Worker {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;
    private Position position;
    private String email;
}

这是数据在数据库中的显示方式:

worker
id      first_name      last_name       position        email
0       Adam            Applegate       Unspecified     adam@company.com
1       Bob             Barrett         Specialist      bob@company.com

所以基本上，当我调用 workerRepository.findById(0); 时我取回的 worker 对象具有以下值:

id --> 0
firstName --> Adam
lastName --> Applegate
position --> Position.UNSPECIFIED
email --> adam@company.com

现在，假设我创建了一个具有以下值的新工作对象:

firstName --> Chad
lastName --> Carlton
position --> Position.NOT_SPECIFIED
email --> chad@company.com

调用后 workerRepository.save(newWorker);数据库应如下所示:

id      first_name      last_name       position        email
0       Adam            Applegate       Unspecified     adam@company.com
1       Bob             Barrett         Specialist      bob@company.com
2       Chad            Carlton         Not Specialist  chad@company.com

请注意，位置列的值为 Position.NOT_SPECIALIST.getName()。

有没有办法在 hibernate 中做到这一点？

Answer 1

正如@chrylis 所建议的，我的问题的答案是使用 AttributeConverter ，像这样:

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

@Converter(autoApply = true)
public class PositionConverter implements AttributeConverter<Position, String> {

    @Override
    public String convertToDatabaseColumn(Position attribute) {
        return attribute.getName();
    }

    @Override
    public VolleyballPlayerPosition convertToEntityAttribute(String dbData) {
        return Position.from(dbData);
    }
}