在xml中定义的Hibernate一对多关系不起作用

Question

帖子很长但是因为我想解释一切足以让你帮助我的事情。我创建了两个表，我想使用hibernate创建一对多关系（每个客户可以有很多订单）。我创建这个表的方式如下所示：

create table if not exists customer(
    customer_id int not null auto_increment,
    first_name varchar(50),
    last_name varchar(50),
    primary key (customer_id)
);

create table if not exists orders(
    order_id int not null auto_increment,
    order_date timestamp not null default current_timestamp,
    adress varchar(50),
    customer int not null,
    primary key (order_id),
    foreign key (customer) references customer(customer_id)
);

现在我想创建java项目并使用hibernate将该项目与我的数据库连接。

pom.xml中的依赖项：

<dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.15</version>
            </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>3.6.3.Final</version>
        </dependency>

        <dependency>
            <groupId>javassist</groupId>
            <artifactId>javassist</artifactId>
            <version>3.12.1.GA</version>
        </dependency>

hibernate.cfg.xml：

 <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
    <hibernate-configuration>
        <session-factory>
            <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
            <property name="hibernate.connection.url">jdbc:mysql://localhost/test</property>
            <property name="hibernate.connection.username">root</property>
            <property name="hibernate.connection.password">root</property>
            <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
            <mapping resource="application.hbm.xml" />
        </session-factory>
    </hibernate-configuration>

application.hbm.xml，其中我在实体和数据库列之间创建连接：

  <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="entity.Customer" table="customer">
        <id name="idCustomer" column="customer_id">
            <generator class="increment" />
        </id>
        <property name="firstName" column="first_name" />
        <property name="lastName" column="last_name" />
        <set name="orders" inverse="true" cascade="persist" >
            <key column="order_id" />
            <one-to-many class="entity.Order" />
        </set>
    </class>

    <class name="entity.Order" table="orders">
        <id name="idOrder" column="order_id">
            <generator class="increment"></generator>
        </id>
        <property name="orderDate" column="order_date"></property>
        <property name="adress" column="adress"></property>
        <many-to-one name="customer" column="customer" not-null="true" />
    </class>

</hibernate-mapping>

客户实体：

package entity;

import java.util.Set;

public class Customer {

    private long idCustomer;
    private String firstName;
    private String lastName;
    private Set<Order> orders;
    public long getIdCustomer() {
        return idCustomer;
    }
    public void setIdCustomer(long idCustomer) {
        this.idCustomer = idCustomer;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public Set<Order> getOrders() {
        return orders;
    }
    public void setOrders(Set<Order> orders) {
        this.orders = orders;
    }
    @Override
    public String toString() {
        String returnString =  "Customer [firstName=" + firstName + ", lastName=" + lastName + "]";
        returnString += "\nOrders: ";
        for(Order order : orders) {
            returnString = returnString +"\n" +  order;
        }

        return returnString;
    }
}

订单实体：

package entity;

import java.util.Date;

public class Order {
    private int idOrder;
    private Date orderDate;
    private String adress;
    private Customer customer;

    public int getIdOrder() {
        return idOrder;
    }

    public void setIdOrder(int idOrder) {
        this.idOrder = idOrder;
    }

    public Date getOrderDate() {
        return orderDate;
    }

    public void setOrderDate(Date orderDate) {
        this.orderDate = orderDate;
    }

    public String getAdress() {
        return adress;
    }

    public void setAdress(String adress) {
        this.adress = adress;
    }

    public Customer getCustomer() {
        return customer;
    }

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

    @Override
    public String toString() {
        return "Order [idOrder=" + idOrder + ", orderDate=" + orderDate + ", adress=" + adress + "]";
    }
}

直到这一刻，一切正常，当我在main方法中运行这样的代码时：

        Configuration conf = new Configuration().configure();
        SessionFactory factory = conf.buildSessionFactory();
        Session session = factory.openSession();

        Customer customer = (Customer) session.get(Customer.class, 1l);


        Transaction transaction = session.beginTransaction();
        Order order = new Order();
        order.setAdress("plac strzelecki 212");
        order.setOrderDate(new Date());
        order.setCustomer(customer);

        customer.getOrders().add(order);
        session.save(customer);
        transaction.commit();

        session.close();

订单保存在数据库中。但在尝试加载此客户并显示其订单后，代码显示客户没有订单...例如，当我这样做时：

Configuration conf = new Configuration().configure();
    SessionFactory factory = conf.buildSessionFactory();
    Session session = factory.openSession();

    Customer customer = (Customer) session.get(Customer.class, 1l);


    System.out.println(customer.getOrders().size());

    session.close();

输出为0 ......我做错了什么？或者我不理解的是什么？