迈出使用 hibernate 和 postgres 的第一步，我为我的实体类创建了旧样式的 xml 配置，并创建了一些 dao 实现，如（Manning Java Persistence with Hib）一书中所述，并创建了一个 HibernateUtil 类来创建 SessionFactory。为了测试这些，我创建了一些实体并试图通过道来拯救。
在此代码中，客户类有一组“订单”。为了配置它，我创建了 hbm.xml 文件，如下所示。
在 demo() 方法中，我创建了实体实例并通过 dao 调用了 saveOrUpdate()。它成功运行并在 db 中创建了两个客户和一个订单。但是，当我尝试将订单添加到客户时，它会导致 RuntimeException 并回滚事务。当我尝试调试应用程序时，我发现
org.hibernate.context.ThreadLocalSessionContext.TransactionProtectionWrapper.invoke() ---> lang.reflect.Method.invoke() ---> java.lang.reflect.InvocationTargetException
我很困惑为什么会发生这种情况。如果我不调用 addOrdersToCustomers()，则不会发生此错误。如果我不调用该方法，这是否意味着客户对象没有订单集？在数据库中，订单表有一个 FK customer_id，它已成功设置为客户的 ID，因为 createOrders() 方法设置了客户客户实例的订单字段。但是，这不会更新客户的设置订单字段。
知道如何纠正这个问题吗？谢谢，
吉姆
public class Main {
CustomerDao custdao;
OrderDao orderdao;
Customer mark,jon;
Order order1,order2,order3;
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd");
public void demo()throws ParseException{
custdao = Daofactory.getCustomerDao();
orderdao = Daofactory.getOrderDao();
createCustomers();
createOrders();
//addOrdersToCustomers();//uncommenting this causes RuntimeException
updateEntities();
}
private void updateEntities() {
Transaction tx = null;
Session session = HibernateUtil.getCurrentSession();
logger.info("got session:"+session);
try{
tx = session.beginTransaction();
logger.info("got transaxion:"+tx);
custdao.saveOrUpdateCustomer(mark);
custdao.saveOrUpdateCustomer(jon);
orderdao.saveOrUpdateOrder(order1);
tx.commit();
}catch(Exception e){
tx.rollback();
}
}
private void addOrdersToCustomers() {
mark.getOrders().add(order1);
}
private void createCustomers() {
mark = new Customer();
mark.setName("mark");
mark.setEmailAddress("mark@home");
mark.setAddress("121,3rd avenue");
mark.setCity("San Diego");
mark.setState("CA");
mark.setCountry("U.S.A");
jon = new Customer();
jon.setName("jon");
jon.setEmailAddress("jon@home");
jon.setAddress("1121 vpura");
jon.setCity("bangalore");
jon.setState("karnataka");
jon.setCountry("india");
}
private void createOrders() throws ParseException {
order1 = new Order();
order1.setCustomer(mark);
order1.setOrderNumber(Long.parseLong("111111111"));
order1.setOrderDate(sdf.parse("2001/01/02"));
...
}
...
public static void main(String[] args) throws ParseException {
new Main().demo();
}
}
映射如下，
public class Customer {
private Long customer_id;
...
private Set<Order> orders;
public Customer() {
super();
orders = new HashSet<Order>();
}
...
}
<hibernate-mapping package="org.me.hibernatestore">
<class name="Customer" table="CUSTOMER">
<id column="CUSTOMER_ID" name="customer_id" type="java.lang.Long">
<generator class="native"/>
</id>
...
<set name="orders" table="ORDERS" lazy="false" cascade="delete-orphan">
<key column="CUSTOMER_ID"/>
<one-to-many class="Order" />
</set>
</class>
</hibernate-mapping>
订单.java
public class Order {
private Long order_id;
...
private Customer customer;
...
}
订单.hbm.xml
...
<class name="Order" table="ORDERS">
<id name="order_id" column="ORDER_ID" type="long">
<generator class="native"/>
</id>
...
<many-to-one name="customer" class="Customer" column="CUSTOMER_ID" lazy="false" />
...
dao 实现有一个基类
public class BaseDaoImpl<T, ID extends Serializable> implements BaseDao<T,ID>{
private Class<T> persistentClass;
private Session session;
public BaseDaoImpl() {
this.persistentClass = (Class<T>)(((ParameterizedType)this.getClass().getGenericSuperclass()).getActualTypeArguments()[0]);
}
public Session getSession() {
if (session == null){
return HibernateUtil.getCurrentSession();
}
return session;
}
...
}
HibernateUtil.java
public class HibernateUtil {
private static SessionFactory sessionFactory;
static {
try {
sessionFactory = new Configuration().configure().buildSessionFactory();
}catch (Throwable ex) {
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
public static Session getCurrentSession(){
Session session = sessionFactory.getCurrentSession(); l
return session;
}