Question

您好，我是hibernate的新手。我有一个类Customer与Order类有一对多的关系，Oder类与Item类有一对多的关系，而且有许多与Customer的一对多。与Item类有一对多的关系产品类别。我的hbm.xml如下所示

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.xyz.hibernet.dto.Customer" table="CUSTOMER" abstract="true">
        <id name="cid"  type="java.lang.Integer" column="CUST_ID" >
        <generator class="native"/>
         </id>
        <property name="cname" column="CUST_NAME"/>
        <list name="orderList" cascade="all">
           <key column="CUST_ID"/>
           <index column="idx"/>
            <one-to-many class="com.activenet.hibernet.dto.Order"/>
         </list>
    </class>



    <class name="com.xyz.hibernet.dto.Order" table="ORDER">
        <id name="oid" type="java.lang.Integer" column="O_ID" >
             <generator class="native"/>
        </id>
        <property name="odate" column="ORDER_DATE"/>
        <property name="amt" column="AMOUNT"/>
        <set name="itemSet" inverse="true" cascade="all">
            <key column="O_ID"/>
            <one-to-many class="com.activenet.hibernet.dto.Item"/>
        </set>
        <many-to-one name="oCustomer" class="com.activenet.hibernet.dto.Customer" column="CUST_ID"/>
    </class>

    <class  name="com.xyz.hibernet.dto.Item" table="ITEM">

        <id name="iid" type="java.lang.Integer" column="ITEM_ID" >
             <generator class="native"/>
        </id>
        <property name="quantity" column="ORDER_QTY"/>
        <many-to-one name="product" class="com.activenet.hibernet.dto.Product" column="PRODUCT_ID"/>
    </class>
    <class  name="com.xyz.hibernet.dto.Product" table="PRODUCT">

        <id name="pid" type="java.lang.Integer" >
            <column name="PROD_ID" />
            <generator class="native"/>
        </id>
        <property name="pname" column="PROD_NAME"/>
        <property name="price" column="PROD_PRICE"/>
        <property name="descr" column="PROD_DESC"/>

    </class>

<!--    <query name="findAllCustomers">
    <![CDATA[from com.xyz.hibernet.dto.Customer c where c.name=:name]]>
    </query>-->

</hibernate-mapping>

并且

客户类如下所示

 import java.util.List;

 public class Customer {

private int cid;
private String cname;
private List orderList;

public Customer()
{
    super();
}
public Customer(int cid,String cname, List orderList)
{
    super();
    this.cid=cid;
    this.cname=cname;
    this.orderList=orderList;
}
--setter and getter 
 }

Product.java

   public class Product {

private int pid;
private String pname;
private double price;
private String descr;

public Product() {
    super();
}

public Product(int pid,String pname,double price,String descr) {
    super();
    this.pid=pid;
    this.pname=pname;
    this.price=price;
    this.descr=descr;
}

Setter and getter methods----here   
}

Order.java

  public class Order {

private int oid;
private Date odate;
private double amt;
private Set itemSet;
private Customer oCustomer;

    public Order()
{
    super();
}
   public Order(int oid,Date odate,double amt, Set itemSet)
   {
 super();
 this.oid=oid;
 this.odate=odate;
 this.itemSet=itemSet;
 this.amt=amt;
   }
 -- setter and getter
   }

Item.java

  public class Item {

private int iid;
private Product product;
private int quantity;
public Item ()
{
    super();
}

public Item (int iid,Product product,int quantity)
{
    super();
    this.iid=iid;
    this.product=product;
    this.quantity=quantity;
}

}

我的测试类如下所示

    public class TestCustomer {

public static void main(String args[])
{
    SessionFactory oSessionFac=new Configuration().configure().buildSessionFactory();
    Session oSession=oSessionFac.openSession();
    Transaction oTransaction=oSession.beginTransaction();

    //-------------------------->New product Insertion<-------------------------------

    Product product1=new Product(0,"Master in EJB",350.00,"Good Luck");
    Product product2=new Product(0,"Master in STRUTS",250.00,"Good Luck");
    Product product3=new Product(0,"Master in WEBSERVICE",150.00,"Good Luck");
    Product product4=new Product(0,"Master in JSF",450.00,"Good Luck");
    Product product5=new Product(0,"Master in SPRING",550.00,"Good Luck");
    oSession.save(product1);
    oSession.save(product2);
    oSession.save(product3);
    oSession.save(product4);
    oSession.save(product5);
    oTransaction.commit();
    System.out.println("::::::::::::product is inserted::::::::::::::");
    //<----------------------Place One Order into new Customer------------------------>

    Product prod1=(Product)oSession.load(Product.class, 1);

    Product prod2=(Product)oSession.load(Product.class, 2);

    Product prod3=(Product)oSession.load(Product.class, 3);

    Item oItem1 =new Item(0,prod1,1);

    Item oItem2 =new Item(0,prod2,1);

    Item oItem3 =new Item(0,prod3,1);

    Item oItem4 =new Item(0,prod1,2);
    Set<Item> set=new HashSet<Item>();
    set.add(oItem1);set.add(oItem2);set.add(oItem3);set.add(oItem4);

    Order oOrder=new Order(0,Calendar.getInstance().getTime(),1200.00,set);

    List<Order> list=new ArrayList<Order>();
    list.add(oOrder);
    oSession.persist(oOrder);
    Customer customer1=new Customer(0,"ABC",list);
    //oOrder=new Order(0,Calendar.getInstance().getTime(),1200.00,set,customer1);
    oSession.saveOrUpdate(customer1);

    oTransaction.commit();
    oSession.flush();
    }

}

我使用过org.hibernate.dialect.MySQLMyISAMDialect方言

在尝试执行代码时，它正在说您的SQL语法中有错误;检查与MySQL服务器版本对应的手册，以便在第1行的'ORDER（ORDER_DATE，AMOUNT，CUST_ID）值（'2012-03-07 11:58:55'，1200.0，null）附近使用正确的语法< / strong>

我尝试了很多但无法修复它。请任何人帮我解决问题

Answer 1

由于Customer（即oCustomer）中的Order（即oOrder）实例未设置（即为NULL），因此hibernate将为列{{}插入NULL 1}}。它绝对会抛出错误，因为此列对客户的FK约束不能接受NULL。

首先，让订单有责任通过将客户内ORDER.CUST_ID的{{1}}属性设置为true来处理客户与订单之间的关系。

（初学者IMO很难理解PS inverse属性，但您可以轻松搜索有关此属性的许多资源。通常，在<set>关系中，我们将其设置为{{1在集合标记中（即inverse，<one-to-many>））

然后在保存之前将customer1设置为oOrder的客户，喜欢这个：

true

休眠中的一对多和多对一关系

1 个答案: