您可以删除@JoinColumn注解，并简单地将两个实体中的关系更改为@ManyToMany。然后在PurchaseOrder中使用List. JPA Package 组件字段，然后自动创建一个名为purchase_order_component的表，该表将保存两个实体的ID。
purchaseOrder应该是这样的：

@Entity
@Table(name = "purchase_order")
public class PurchaseOrder {
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Id
@Column(name = "id", nullable = false)
private Integer id;
@Enumerated
@Column(name = "status")
private PurchaseOrderStatus purchaseOrderStatus;
@ManyToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
@JoinColumn(name = "user_id", nullable = false, foreignKey = 
@ForeignKey(name = "FK_PO_USER"))
private User user;
@ManyToMany(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
List<Component> component;
}

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和组件：

@Entity
@Table(name = "components", schema = "public")
public class Component {
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Id
@Column(name = "id", nullable = false)
private Integer id;
private Integer qty;
@ManyToMany(mappedBy = "component")
@ToString.Exclude
List<PurchaseOrder> purchaseOrders;
}

型
你可以让spring为你添加这个属性来生成数据库模式：

spring.jpa.hibernate.ddl-auto=update

型
或者这里是SQL等价物：

CREATE TABLE components (
    id serial4 NOT NULL,
    qty int4 NULL,
    CONSTRAINT components_pkey PRIMARY KEY (id)
);
CREATE TABLE users (
    id serial4 NOT NULL,
    CONSTRAINT users_pkey PRIMARY KEY (id)
);
CREATE TABLE purchase_order (
    id serial4 NOT NULL,
    user_id int4 NOT NULL,
    CONSTRAINT purchase_order_pkey PRIMARY KEY (id),
    CONSTRAINT fk_po_user FOREIGN KEY (user_id) REFERENCES users(id)
);
CREATE TABLE purchase_order_component (
    purchase_orders_id int4 NOT NULL,
    component_id int4 NOT NULL,
    CONSTRAINT fk_po FOREIGN KEY (purchase_orders_id) REFERENCES purchase_order(id),
    CONSTRAINT fk_component FOREIGN KEY (component_id) REFERENCES components(id)
);

型