Hibernate 表关系描述之OneToMany

Hibernate 表关系描述之OneToMany
上篇写了一对一，那么在这篇我们讲一对多，那么在表中的一对多，是使用外键关联，通过一张表的一个键另一个表的外键来建立一多关系;
而在类中表示为一个类中有一个集合属性包含对方类的很多对象，而在另一个类中，只包含前术类的一个对象，从而实现一对多关系的建立！
而在Hibernate中采用的是Set类型集合，而使用<one-to-many>主<many-to-one>来实现，好了，我们来看一下：
首先看看表结构！

customer表:

create table customers
(
    ID bigint not null    primary key auto_increment,
    userName varchar(20)
);Order表: create table orders
(
    ID bigint not null primary key auto_increment,
    customers_ID bigint,    --应该为customers(ID)外键
    orderDescription varchar(50)--订单描述
);

有了上面简单的客户表与订单表，来建立一个Project!~并且添加Hibernate~并由上面二张表生成Beans,主键都是native类型～自动递增！
我们将自动生成的Customer.java Bean添加一个SET属性，代码如下：

package fengyan.Hibernate;

import java.util.HashSet;
import java.util.Set;

/**
*Authod: fengyan
* date: 2006-12-30 01:02
*/

public class Customers implements java.io.Serializable {

// Fields

private Long id;
private String userName;

     //必须定义一个Set集合类型的属性以及它的get和set方法，
     //它持有一个Customers对象所发出的所有订单的引用
     private Set orders = new HashSet();

// Constructors

    public Set getOrders() {
        return orders;
    }

    public void setOrders(Set orders) {
        this.orders = orders;
    }

    /** default constructor */
    public Customers() {
    }

    /** full constructor */
    public Customers(String userName) {
        this.userName = userName;
    }

// Property accessors

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUserName() {
        return this.userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

}

为Order.java Bean 去掉cid(CustomerID)并添加一个Customer属性，代码如下：

package fengyan.Hibernate;
/**
*Authod: fengyan
* date: 2006-12-30 01:02
*/

public class Orders implements java.io.Serializable {

// Fields

     private Long id;
//   private Long customersId;
     private String orderDescription;

     //添加一个Customers属性，用来引用一个订单对象所属的客户对象
     private Customers customer;
    // Constructors

    public Customers getCustomer() {
        return customer;
    }

    public void setCustomer(Customers customer) {
        this.customer = customer;
    }

    /** default constructor */
    public Orders() {
    }

    public Orders(String description)
    {
        this.orderDescription = description;
    }

    // Property accessors

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getOrderDescription() {
        return this.orderDescription;
    }

    public void setOrderDescription(String orderDescription) {
        this.orderDescription = orderDescription;
    }
}

修改Customer.hbm.xml映射文件:

<?xml version="1.0" encoding="GBK"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="fengyan.Hibernate.Customers" table="customers" catalog="study">
        <id name="id" type="java.lang.Long">
            <column name="ID" />
            <generator class="native" />
        </id>
        <property name="userName" type="java.lang.String">
            <column name="userName" length="20" />
        </property>

        
        <set name="orders" table="orders" cascade="save-update" inverse="true">
            <key column="customers_ID"></key>
            <one-to-many class="fengyan.Hibernate.Orders"/>
        </set>
    </class>
</hibernate

补充：web前端 , JavaScript ,