休眠复合键映射外键问题

Question

这是我的MySQL db

用户.java

@Entity
@Table(name="user")
public class user 
{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private int uid;
   @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy ="user")
   private Set<order> orders = new HashSet<order>();
   //
   setter ,getter  ,and other 
}

序.java

@Entity
@Table(name="`order`")
public class order 
{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private int oid;
   @OneToMany(cascade = CascadeType.ALL)
   @JoinColumn(name="oid", referencedColumnName="oid" )
   private Set<orderitem> orderitems = new HashSet<orderitem>();
   @ManyToOne(cascade=CascadeType.ALL)
   @JoinColumn(name="uid")
   private user user ;
   /////
   setter ,getter and other
}

订单项.java

@Entity
@Table(name="orderitem")
public class orderitem 
{
   @EmbeddedId
   private orderitem_PK PK; //composite key
   @ManyToOne
   @JoinColumn(name="oid", referencedColumnName="oid" ,insertable = false, updatable = false)
   private order order;
   @ManyToOne
   @JoinColumn(name="pid", referencedColumnName="pid", insertable = false, updatable = false)
   private product products ;
   ////
   setter,getter and other
}

orderitem_PK.java

@Embeddable
public class orderitem_PK implements Serializable
{
    private int oid;
    private int pid;
    public orderitem_PK() {}
    public orderitem_PK(int oid, int pid) {
        this.oid = oid;
        this.pid = pid;
    }
    // equals, hashCode
    @Override
    public boolean equals(Object obj) {
        // TODO Auto-generated method stub
        return super.equals(obj);
    }
    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        return super.hashCode();
    }

和最后一个产品.java

@Entity
@Table(name="product")
public class product 
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int pid;
    @OneToMany(cascade = CascadeType.ALL )
    @JoinColumn(name="pid", referencedColumnName="pid" )
    private Set<orderitem> orderitems = new HashSet<orderitem>();
     //////////
        setter,getter and other
}

这是一个在线购物页面

我正在尝试通过此代码插入数据

             order order = new order();
             order.setUser(user);
             order.setOrdertotal(product.getPrice());
             Date dt = new Date();
             DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
             String nowTime = df.format(dt);
             java.sql.Timestamp buydate = java.sql.Timestamp.valueOf(nowTime); 
             order.setOrderdate(buydate);
             /// delete this part will work 
             orderitem orderitem = new orderitem();
             orderitem.setOrder(order);
             orderitem.setProducts(product);
             orderitem.setQuantity(product.getQuantity());
             orderitem.setPrice(product.getPrice());
             ////
             session.save(order);
             session.save(orderitem);

遇到一些错误。

org.hibernate.id.IdentifierGenerationException： null id 生成：class Model.orderitem

当我只保存用户和订购部分代码时，代码是工作。

添加保存订单项代码后，出现问题。

我认为复合键映射外键是错误的。

但我不知道如何解决它.

谁能发现我做错了什么？

谢谢。

Answer 1

您需要

使用 @MapsId 在 EmbeddedId 中映射 oid 和 pid。@MasId提供父实体的嵌入 Id 主键或简单主键的映射。在订单项实体中进行以下更改。

@Entity
@Table(name="orderitem")
public class orderitem 
{
   @EmbeddedId
   private orderitem_PK PK; //composite key
   @ManyToOne
   @MapsId("oid") // maps the order id attribute of embedded id
   @JoinColumn(name="oid", referencedColumnName="oid" ,insertable = false, updatable = false)
   private order order;
   @ManyToOne
   @MapsId("pid") // maps the product id attribute of embedded id
   @JoinColumn(name="pid", referencedColumnName="pid", insertable = false, updatable = false)
   private product products ;
   ////
   setter,getter and other
}