如何使用 JPA 注释引入多列约束？

我试图在 JPA 映射的实体上引入一个多键约束:

public class InventoryItem {
@Id
private Long id;


@Version
private Long version;


@ManyToOne
@JoinColumn("productId")
private Product product;


@Column(nullable=false);
private long serial;
}

基本上(产品，系列)对应该是独一无二的，但我只找到了一种方法来说，系列应该是独一无二的。这显然不是一个好主意，因为不同的产品可能有相同的序列号。

有没有一种方法可以通过 JPA 生成这个约束，或者我必须手动创建它到数据库？

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小开

最佳答案

You can declare unique constraints using the @Table(uniqueConstraints = ...) annotation in your entity class, i.e.

@Entity
@Table(uniqueConstraints={
@UniqueConstraint(columnNames = {"productId", "serial"})
})
public class InventoryItem {
...
}

Note that this does not magically create the unique constraint in the database, you still need a DDL for it to be created. But seems like you are using some sort of automated tool for creating the database based on JPA entity definitions.

小开

As already answered, multi-column index can be added using @Table annotation. However, columnNames needs to be the name of actual DB columns, not the class attribute. So, if the column is like the following:

@Column(name="product_id")
Long productId;

Then the @Table annotation should be like the following

@Table(uniqueConstraints=
@UniqueConstraint(columnNames = {"product_id", "serial"}))