java – org.hibernate.PersistentObjectException：分离的实体

发布时间：2020-12-14 16:36:56 所属栏目：Java 来源：网络整理

导读：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

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() {
    }
}

（编辑：李大同）

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