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JPA中的复合键

compound-key annotations jpa java

8

homaxto · 技术社区 · 16 年前

我之所以要这样做,是因为主键应该在另一个表中用作外键,而使其复合将不好。

@Entity
@Table(name = "dm_action_plan")
public class ActionPlan {
    @Id
    private int pk;
    @Column(name = "command", nullable = false)
    private String command;
    @Column(name = "model", nullable = false)
    String model;
}

2 回复 | 直到 13 年前

1

18

Steve McNail Michel 8 年前

你可以用 @UniqueConstraint 大概是这样的:

@Entity
@Table(name = "dm_action_plan",
       uniqueConstraints={ @UniqueConstraint(columnNames= "command","model") } )
public class ActionPlan {
    @Id
    private int pk;

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

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

这将允许JPA实现为唯一约束生成DDL。

2

0

Nicolas 16 年前

使用@GeneratedValue表示将生成密钥,@UniqueConstraint表示唯一性

@Entity
@Table(name = "dm_action_plan"
       uniqueConstraint = @UniqueConstraint({"command", "model"})
)
public class ActionPlan {
    @Id
    @GeneratedValue
    private int pk;
    @Column(name = "command", nullable = false)
    private String command;
    @Column(name = "model", nullable = false)
    String model;
}