Java JPA对象[]不是已知的实体类型
我有一个JPA,我试图从Oracle数据库检索数据。我在加载页面时出现以下错误: java.lang.IllegalArgumentException:对象:[com.ProEJT。Order@1f7be7b,com.ProEJT。Order@1fa8988,com.ProEJT。Order@15b44d6,com.ProEJT。Order@1044daf,com.ProEJT。Order@1882d18,com.ProEJT。Order@389922,com.ProEJT。Order@1cda81e,com.ProEJT。Order@d86c58,com.ProEJT。Order@b1404f,com.ProEJT。Order@f5331a,com.ProEJT。Order@1ee145b,com.ProEJT。Order@17a687b,com.ProEJT。Order@16181be,com.ProEJT.Order@8d12e4,com.ProEJT。Order@1d35bf2,com.ProEJT。Order@1398044,com.ProEJT。Order@141d19,com.ProEJT。Order@825459,com.ProEJT。Order@6fb3d6,com.ProEJT。Order@1602bbc,com.ProEJT。Order@d75cf7,com.ProEJT。Order@1186cf9]不是已知的实体类型 我唯一的实体类是Order:Java JPA对象[]不是已知的实体类型,java,jpa,Java,Jpa,我有一个JPA,我试图从Oracle数据库检索数据。我在加载页面时出现以下错误: java.lang.IllegalArgumentException:对象:[com.ProEJT。Order@1f7be7b,com.ProEJT。Order@1fa8988,com.ProEJT。Order@15b44d6,com.ProEJT。Order@1044daf,com.ProEJT。Order@1882d18,com.ProEJT。Order@389922,com.ProEJT。Order@1cda
package com.ProEJT;
import java.sql.Date;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity(name="Orders")
@Table(name="Orders")
public class Order
{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
int id;
private Date created;
private String sender;
private String receiver;
private String input;
private String output;
private String state;
public Order() {
}
public Order(int id, Date date, String sender, String receiver, String input, String output, String state)
{
this.id = id;
this.created = date;
this.sender = sender;
this.receiver = receiver;
this.input = input;
this.output = output;
this.state = state;
}
public int getId()
{
return id;
}
public void setId(int id)
{
this.id = id;
}
public Date getCreated()
{
return created;
}
public void setCreated(Date date)
{
this.created = date;
}
public String getSender()
{
return sender;
}
public void setSender(String sender)
{
this.sender = sender;
}
public String getReceiver()
{
return receiver;
}
public void setReceiver(String receiver)
{
this.receiver = receiver;
}
public String getInput()
{
return input;
}
public void setInput(String string)
{
this.input = string;
}
public String getOutput()
{
return output;
}
public void setOutput(String string)
{
this.output = string;
}
public String getState()
{
return state;
}
public void setState(String state)
{
this.state = state;
}
}
我用于检索数据的方法如下所示:
public List<Order> getOrderList()
{
factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
EntityManager em = factory.createEntityManager();
try
{
em.getTransaction().begin();
Query q = em.createQuery("Select o from Orders o");
@SuppressWarnings("unchecked")
List<Order> orders = q.getResultList();
List<Order> orders2 = new ArrayList<Order>();
Iterator<Order> iterator = orders.iterator();
while(iterator.hasNext())
{
Order order = (Order)iterator.next();
order.setId(this.id);
order.setCreated(this.created);
order.setSender(this.sender);
order.setReceiver(this.receiver);
order.setInput(this.input);
order.setOutput(this.output);
order.setState(this.state);
orders2.add(order);
}
em.persist(orders2);
em.getTransaction().commit();
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
em.close();
}
return orders;
}
public List getOrderList()
{
factory=Persistence.createEntityManagerFactory(Persistence\u UNIT\u NAME);
EntityManager em=factory.createEntityManager();
尝试
{
em.getTransaction().begin();
Query q=em.createQuery(“从订单o中选择o”);
@抑制警告(“未选中”)
列表顺序=q.getResultList();
List orders2=新的ArrayList();
迭代器迭代器=orders.Iterator();
while(iterator.hasNext())
{
Order Order=(Order)迭代器.next();
order.setId(this.id);
order.setCreated(this.created);
order.setSender(本发送方);
order.setReceiver(此.receiver);
order.setInput(this.input);
order.setOutput(this.output);
order.setState(本状态);
订单2.添加(订单);
}
em.persist(orders2);
em.getTransaction().commit();
}
捕获(例外e)
{
e、 printStackTrace();
}
最后
{
em.close();
}
退货订单;
}
任何帮助都将不胜感激
编辑:
方法2:
public List<Order> getOrderList()
{
factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
Query q = em.createQuery("Select o from Order o");
@SuppressWarnings("unchecked")
List<Order> orders = q.getResultList();
em.persist(orders);
em.getTransaction().commit();
return orders;
}
public List getOrderList()
{
factory=Persistence.createEntityManagerFactory(Persistence\u UNIT\u NAME);
EntityManager em=factory.createEntityManager();
em.getTransaction().begin();
Query q=em.createQuery(“从订单o中选择o”);
@抑制警告(“未选中”)
列表顺序=q.getResultList();
em.persist(订单);
em.getTransaction().commit();
退货订单;
}
您不能持久化整个订单2
,因为ArrayList
不是JPA感知类。您可能应该持久化循环中的每个元素:
while(iterator.hasNext())
{
Order order = (Order)iterator.next();
order.setId(this.id);
order.setCreated(this.created);
order.setSender(this.sender);
order.setReceiver(this.receiver);
order.setInput(this.input);
order.setOutput(this.output);
order.setState(this.state);
orders2.add(order);
em.persist(order);
}
我现在已经编辑了我的代码,将在问题中进行编辑。有人建议我根本不需要迭代,因此我将在问题中添加新方法。为什么调用
em.persist(orders)
在这种情况下?我意识到我对JPA的理解有点不正确,所以我现在对它进行了分类,错误消失了。感谢您调用persist
方法“saves”您在数据库中的实例。在您的情况下,变量orders
已经包含您刚刚使用q.getResultList()从数据库中检索到的所有Order
实例
。为什么要再次保存它们?对persist的调用是多余的…从查询中检索到的对象是被管理的,因此任何更新都将被直接持久化,而无需调用persist。在任何像样的JPA书籍或文档中都有介绍