( 转)Hibernate报错org.hibernate.MappingException: Unknown entity:...解决方法

今天看视频教程学习了一下Hibernate，按照视频教程中的代码写，老师测试通不过，老报错，苦苦找不到原因，最终经过一个下午一个晚上的时间找出了原因，遂记录一下，希望帮助到有需要的人。

先说下报错：
org.hibernate.MappingException: Unknown entity

这句报错的原因是映射没有成功，查看Bean和Hibernate的主配置文件和映射配置文件如下：

Students.java

package cn.codekong.entity;

/**
 * 学生类
 * @author szh
 *
 */
public class Students{
    private int sid;
    private String sname;
    private String gender;
    private String address;

    public Students() {

    }



    public Students(int sid, String sname, String gender, String address) {
        super();
        this.sid = sid;
        this.sname = sname;
        this.gender = gender;
        this.address = address;
    }



    public int getSid() {
        return sid;
    }



    public void setSid(int sid) {
        this.sid = sid;
    }



    public String getSname() {
        return sname;
    }



    public void setSname(String sname) {
        this.sname = sname;
    }



    public String getGender() {
        return gender;
    }



    public void setGender(String gender) {
        this.gender = gender;
    }



    public String getAddress() {
        return address;
    }



    public void setAddress(String address) {
        this.address = address;
    }



    @Override
    public String toString() {
        return "Students [sid=" + sid + ", sname=" + sname + ", gender=" + gender + ", address=" + address + "]";
    }
}
  
  

   
   
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hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql:///hibernate?useUnicode=true&amp;characterEncoding=UTF-8</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <property name="hbm2ddl.auto">create</property>

        <mapping resource="cn/codekong/entity/Students.hbm.xml"/>
    </session-factory>
</hibernate-configuration>
  
  

   
   
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Students.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-4-2 18:05:47 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="cn.codekong.entity.Students" table="STUDENTS">
        <id name="sid" type="int">
            <column name="SID" />
            <generator class="assigned" />
        </id>
        <property name="sname" type="java.lang.String">
            <column name="SNAME" />
        </property>
        <property name="gender" type="java.lang.String">
            <column name="GENDER" />
        </property>
        <property name="address" type="java.lang.String">
            <column name="ADDRESS" />
        </property>
    </class>
</hibernate-mapping>
  
  

   
   
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StudentsTest.java

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import cn.codekong.entity.Students;

public class StudentsTest {
    private SessionFactory sessionFactory;
    private Session session;
    private Transaction transaction;

    @Before
    public void init() {
        //创建配置对象
        Configuration configuration = new Configuration().configure();
        //创建服务注册对象
        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        //创建会话工厂对象
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        //会话对象
        session = sessionFactory.openSession();
        //开启事物
        transaction = session.beginTransaction();
    }

    @After
    public void destory() {
        //提交事物
        transaction.commit();
        //关闭会话
        session.close();
        //关闭会话工厂
        sessionFactory.close();
    }

    @Test
    public void testSaveStudents() {
        //生成学生对象
        Students student = new Students(1, "张三丰", "男", "武当山");
        System.out.println(student);
        session.save(student);
        System.out.println(session);
    }

}
  
  

   
   
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上面的代码看其实确实是对的，但是就是测试跑不通，最终发现是版本问题 ，对，版本问题，视频里面是Hibernate3.x，而我使用的是Hibernate5.x，所以代码有变化。

说明一下，上面的代码在Hibernate5.x以下是可以运行的，但是在Hibernate5.x以后，必须写成如下的形式：

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.service.ServiceRegistry;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import cn.codekong.entity.Students;

public class StudentsTest {
    private SessionFactory sessionFactory;
    private Session session;
    private Transaction transaction;

    @Before
    public void init() {
        //创建服务注册对象
        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build();
        //创建会话工厂对象
        sessionFactory = new MetadataSources(serviceRegistry).buildMetadata().buildSessionFactory();
        //会话对象
        session = sessionFactory.openSession();
        //开启事物
        transaction = session.beginTransaction();
    }

    @After
    public void destory() {
        //提交事物
        transaction.commit();
        //关闭会话
        session.close();
        //关闭会话工厂
        sessionFactory.close();
    }

    @Test
    public void testSaveStudents() {
        //生成学生对象
        Students student = new Students(1, "张三丰", "男", "武当山");
        System.out.println(student);
        session.save(student);
        System.out.println(session);
    }

}
  
  

   
   
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主要的变化就两句代码，便可以解决问题，希望可以帮助到有需要的人。

原文转自:https://blog.csdn.net/bingjianit/article/details/68954250

今天看视频教程学习了一下Hibernate，按照视频教程中的代码写，老师测试通不过，老报错，苦苦找不到原因，最终经过一个下午一个晚上的时间找出了原因，遂记录一下，希望帮助到有需要的人。