Question

我有三张桌子

CREATE TABLE "ingredient" (
  "id" INTEGER GENERATED BY DEFAULT AS IDENTITY(START WITH 1, INCREMENT BY 1) PRIMARY KEY,
  "ingredient" VARCHAR(50) NOT NULL
);


CREATE TABLE "pizza" (
  "id" INTEGER GENERATED BY DEFAULT AS IDENTITY(START WITH 1, INCREMENT BY 1) PRIMARY KEY,
  "pizza" VARCHAR(50) NOT NULL
);


CREATE TABLE "pizza_structure" (
  "pizza_id" INT NOT NULL,
  "ingredient_id" INT NOT NULL,
  "amount" INT NOT NULL
);

如何加入它们，将Pizzas结构作为Map

@Entity
@Table(name = "ingredient")
public class Ingredient{

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String name;

    public Ingredient() {
    }
}


@Entity
@Table(name = "pizza")
public class Pizza {

    @Id
    @GeneratedValue
    private Long id;
    private String name;
    @OneToMany ????
    private Map<Ingredient, Integer> pizzaStructure;

    public Pizza() {
    }

    public Pizza(String name, Map<Long, Integer> pizzaStructure) {
        this.name = name;
        this.pizzaStructure = pizzaStructure;
    }
}

我是否需要创建@Embeddable类PizzaStructure，如果是，如何使用它？

现在我收到了一个错误调用init方法失败;嵌套异常是org.hibernate.AnnotationException：使用@OneToMany或@ManyToMany定位未映射的类：

Answer 1

如何加入它们，将Pizzas结构作为Map

看起来像这样：

@ElementCollection
@CollectionTable(name = "pizza_structure", joinColumns = {@JoinColumn(name = "pizza_id")})
@Column(name = "amount")
@MapKeyJoinColumn(name = "ingredient_id")
private Map<Ingredient, Integer> pizzaStructure;

我是否需要创建@Embeddable类PizzaStructure

没有

更多信息在这里：Hibernate User Guide - Maps。

请注意，表格pizza_structure应包含pizza和ingredient表的外键以及pizza_id和ingredient_id的唯一约束，如下所示（＆＃ 39; postgresql方言）：

create table pizza_structure
(
  pizza_id ... constraint fk_structure_pizza references pizza,
  ingredient_id ... constraint fk_structure_ingredient references ingredient,
  amount ...,
  constraint pizza_structure_pkey primary key (pizza_id, ingredient_id)
);

JPA Entitties，如何连接表

1 个答案: