Hibernate UnknownEntityTypeException报错求助：无法找到实体持久化器

运行基于Hibernate和PostgreSQL的项目时出现报错：

Exception in thread "main" org.hibernate.UnknownEntityTypeException: Unable to locate persister: org.example.entity.Employee

相关代码如下：

Employee实体类 #

package org.example.entity;

import jakarta.persistence.*;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

@Entity
@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
public class Employee {
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Id
    @Column(name = "id", nullable = false)
    private Integer id;
    @Basic
    @Column(name = "name", nullable = true, length = 10)
    private String name;
    @Basic
    @Column(name = "surname", nullable = true, length = 15)
    private String surname;
    @Basic
    @Column(name = "office_id", nullable = true)
    private Integer officeId;
}

hibernate.cfg.xml配置文件 #

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
  <session-factory>
    <property name="connection.url">jdbc:postgresql://localhost:5432/postgres</property>
    <property name="connection.driver_class">org.postgresql.Driver</property>
    <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</property>
    <property name="connection.username">postgres</property>
    <property name="connection.password">vfr4vgy7</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="hibernate.show_sql">true</property>

    <mapping class="org.example.entity.Employee"/>

      <!-- DB schema will be updated if needed -->
    <!-- <property name="hibernate.hbm2ddl.auto">update</property> -->
  </session-factory>
</hibernate-configuration>

Main主类 #

package org.example;

import org.example.entity.Employee;
import org.hibernate.Session;

public class Main {
    public static void main(String[] args) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        Employee employee = new Employee();
        employee.setName("New");
        employee.setSurname("Hero");
        employee.setOfficeId(1);
        employee.setId(12);
        session.beginTransaction();
        session.save(employee);
        session.getTransaction().commit();
        session.close();
        HibernateUtil.close();
    }
}

HibernateUtil工具类 #

package org.example;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

/**
 * Created by Ариорх on 27.05.2017.
 */
public class HibernateUtil {
    private static SessionFactory sessionFactory = null;

    static {
        Configuration cfg = new Configuration().configure();
        StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()
                .applySettings(cfg.getProperties());
        sessionFactory = cfg.buildSessionFactory(builder.build());
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void close(){
        getSessionFactory().close();
    }
}

使用环境：PostgreSQL数据库、IntelliJ IDEA Ultimate版本，疑问：该报错是否因HibernateUtil类导致，如何解决？

这个报错的核心是Hibernate无法找到Employee实体的持久化器，HibernateUtil的写法确实是主要原因之一，以下是具体分析和修复步骤：

1. HibernateUtil的错误修复 #

原HibernateUtil在构建SessionFactory时，没有将配置中的实体映射信息正确关联到StandardServiceRegistry，导致SessionFactory无法识别实体类。

修改后的HibernateUtil：

package org.example;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static SessionFactory sessionFactory = null;

    static {
        try {
            Configuration cfg = new Configuration().configure();
            StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
                    .applySettings(cfg.getProperties())
                    .build();
            // 确保配置中的实体映射被加载到SessionFactory
            sessionFactory = cfg.buildSessionFactory(registry);
        } catch (Throwable ex) {
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void close(){
        getSessionFactory().close();
    }
}

或者采用Hibernate 5.2+推荐的更简洁写法：

package org.example;

import org.hibernate.SessionFactory;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

public class HibernateUtil {
    private static StandardServiceRegistry registry;
    private static SessionFactory sessionFactory;

    public static SessionFactory getSessionFactory() {
        if (sessionFactory == null) {
            try {
                registry = new StandardServiceRegistryBuilder().configure().build();
                Metadata metadata = new MetadataSources(registry).getMetadataBuilder().build();
                sessionFactory = metadata.getSessionFactoryBuilder().build();
            } catch (Exception e) {
                e.printStackTrace();
                if (registry != null) {
                    StandardServiceRegistryBuilder.destroy(registry);
                }
            }
        }
        return sessionFactory;
    }

    public static void close() {
        if (registry != null) {
            StandardServiceRegistryBuilder.destroy(registry);
        }
    }
}

2. 其他可能的排查点 #

• 依赖版本匹配：实体类使用了jakarta.persistence.*包，说明是Hibernate 6.x或Jakarta EE版本，确保项目依赖中Hibernate版本与JPA规范匹配，避免javax.persistence和jakarta.persistence包冲突。
• 实体扫描配置：若修改HibernateUtil后仍报错，可在hibernate.cfg.xml中添加自动扫描配置：

  <property name="hibernate.archive.autodetection">class,hbm</property>
  

• 映射路径验证：确认<mapping class="org.example.entity.Employee"/>的类路径拼写完全正确，实体类确实位于org.example.entity包下。
• 编译输出检查：在IntelliJ IDEA中，确认实体类已正确编译到target/classes目录，无编译错误。

内容的提问来源于stack exchange，提问作者tonan