我正在尝试使用连接语句中的常量值连接同一个表中的不同实体。在 SQL 中,我会做这样的事情......
SELECT *
FROM owner o
JOIN types t on t.owner_id = o.id AND t.type = 'A'
-- ^^^^^^^^^^^^^^^^ THIS IS WHAT I AM TRYING TO REPLICATE
在 Java + JPA/Hibernate 中,我正在尝试做这样的事情......
@Entity
@Table(name = "OWNER")
public class Owner {
@Id
@Column(name="ID")
private Long id
@OneToOne(mappedBy = "owner", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumns({
@JoinColumn(name = "ID", referencedColumnName = "ID"),
@JoinColumn(constantValue = "A", referencedColumnName="type")})
// ^^^^^^^^^^^^^^^^^^^ I AM LOOKING FOR SOMETHING THAT DOES THIS.
// constantValue IS NOT A VALID ARGUMENT HERE.
private TypeA inspectionSnapshot;
@OneToOne(mappedBy = "owner", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumns({
@JoinColumn(name = "ID", referencedColumnName = "ID"),
@JoinColumn(constantValue = "B", referencedColumnName="type")})
private TypeB inspectionSnapshot;
/* Getters & Setters ... */
}
@Entity
@Table(name = "TYPES")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "TYPE", discriminatorType = DiscriminatorType.STRING)
public abstract class BaseType {
@Id
@OneToOne
@JoinColumn(name = "OWNER_ID", referencedColumnName="ID")
private Owner id;
@Id
@Column(name = "TYPE")
private char type
/* Getters & Setters ... */
}
@Entity
@DiscriminatorValue("A")
public class TypeA extends BaseType {
/* All functionality in BaseType */
}
@Entity
@DiscriminatorValue("B")
public class TypeA extends BaseType {
/* All functionality in BaseType */
}
提前致谢!
最佳答案
尝试指定一个常量作为公式的值
@JoinColumnsOrFormulas({
@JoinColumnOrFormula(formula=@JoinFormula(value="'A'", referencedColumnName="type")),
@JoinColumnOrFormula(column = @JoinColumn("id", referencedColumnName="id"))
})
private TypeA inspectionSnapshot;
关于java - JPA/Hibernate 加入常量值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28818511/