我正在创建一个简单的应用程序,只需在表中插入一行(如果表不存在,创建它)使用
Java JPA.
我已经在google上看过,在这里,我仍然不明白这是什么异常.即使这里有与我同样的问题的问题,但我没有得到解决方案.我还是Java JPA的新手,所以请光着我.
我附加了一些代码来运行它的例子.
回到这个问题,这是我得到的异常和stacktrace：
EXCEPTION -- > org.hibernate.PersistentObjectException: detached entity passed to persist: view.Person
javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: view.Person
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1683)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1187)
at view.TestJPA.main(TestJPA.java:34)
Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist: view.Person
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:139)
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75)
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1181)
... 1 more
这里是我的代码：
主班：
package view;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
public class TestJPA {
public static void main(String[] args) {
Person p = new Person(1,"Peter","Parker");
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("TesePersistentUnit");
EntityManager entityManager = entityManagerFactory.createEntityManager();
EntityTransaction transaction = entityManager.getTransaction();
try {
transaction.begin();
entityManager.persist(p);
entityManager.getTransaction().commit();
}
catch (Exception e) {
if (transaction != null) {
transaction.rollback();
}
System.out.println("EXCEPTION -- > " + e.getMessage());
e.printStackTrace();
}
finally {
if (entityManager != null) {
entityManager.close();
}
}
}
}
和人类：
package view;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "People")
public class Person {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
private String lastName;
public Person(int id,String name,String lastName) {
this.id = id;
this.name = name;
this.lastName = lastName;
}
public Person() {
}
}
这是我的persistence.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="TesePersistentUnit" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>view.Person</class>
<properties>
<!-- sql dialect -->
<property name="hibernate.dialect" value="org.hibernate.dialect.MysqLDialect"/>
<property name="javax.persistence.jdbc.url" value="jdbc:MysqL://localhost:3306/tese_tabelas?zeroDateTimeBehavior=convertToNull"/>
<property name="javax.persistence.jdbc.user" value="root"/>
<property name="javax.persistence.jdbc.driver" value="com.MysqL.jdbc.Driver"/>
<property name="javax.persistence.jdbc.password" value=""/>
<!-- Create/update tables automatically using mapping Metadata -->
<property name="hibernate.hbm2ddl.auto" value="update"/>
</properties>
</persistence-unit>
</persistence>
———————–编辑————————– –
我只是将提供程序更改为EclipseLink,而无需进一步更改.我现在很困惑.为什么它与EclipseLink一起工作,但是使用Hibernate会产生异常？
解决方法
尝试使用下面的代码,然后,它将允许您手动设置ID.
只需使用@Id注释即可定义哪个属性是您实体的标识符.如果您不希望hibernate为您生成此属性,则不需要使用@GeneratedValue注释.
分配 – 允许应用程序在调用save()之前为对象分配一个标识符.这是默认策略,如果没有< generator>元素被指定.
package view;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "People")
public class Person {
@Id
//@GeneratedValue(strategy = GenerationType.AUTO) // commented for manually set the id
private int id;
private String name;
private String lastName;
public Person(int id,String lastName) {
this.id = id;
this.name = name;
this.lastName = lastName;
}
public Person() {
}
}
