org.hibernate.MappingException: Unknown entity when trying to create a new record

Question

I want to implement simple CRUD operations in MySQL using Hibernate and Spring MVC. I have made a few web apps in Spring MVC but Hibernate is quite new to me. I tried to create a record in one of the tables in my database and followed this tutorial: https://examples.javacodegeeks.com/enterprise-java/hibernate/hibernate-crud-operations-tutorial/ But when I run the application, it gives org.hibernate.MappingException

I have tried both keeping and removing the mapping class line from the file hibernate-cfg.xml. I also checked for missing @Entity annotations.

Exception Stack:

org.hibernate.MappingException: Unknown entity: com.eversoft.traverse.model.User
    at org.hibernate.metamodel.internal.MetamodelImpl.entityPersister(MetamodelImpl.java:704)
    at org.hibernate.internal.SessionImpl.getEntityPersister(SessionImpl.java:1731)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:118)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:191)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:176)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:712)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:704)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:699)
    at com.eversoft.traverse.daoimpl.UserDaoImpl.createUser(UserDaoImpl.java:43)
    at com.eversoft.traverse.serviceimpl.UserServiceImpl.createUser(UserServiceImpl.java:22)
    at com.eversoft.traverse.controller.UserController.addUserDummy(UserController.java:31)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:668)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:791)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1417)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:835)

User.java

package com.eversoft.traverse.model;

import java.io.Serializable;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="users")
public class User implements Serializable{
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="id")
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;

    @Column(name="firstName")
    private String firstName;

    @Column(name="middleName")
    private String middleName;

    @Column(name="lastName")
    private String lastName;

    @Column(name="nationality")
    private String nationality;

    @Column(name="dateOfBirth")
    public Date dateOfBirth;

    @Column(name="visaId")
    private int visaId;

    public User() {

    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getMiddleName() {
        return middleName;
    }

    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getNationality() {
        return nationality;
    }

    public void setNationality(String nationality) {
        this.nationality = nationality;
    }

    public Date getDateOfBirth() {
        return dateOfBirth;
    }

    public void setDateOfBirth(Date dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }

    public int getVisaId() {
        return visaId;
    }

    public void setVisaId(int visaId) {
        this.visaId = visaId;
    }


}

UserController.java

package com.eversoft.traverse.controller;

import java.util.Date;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.eversoft.traverse.model.User;
import com.eversoft.traverse.service.UserService;

@Controller
public class UserController {

    @Autowired
    UserService userService;

    @RequestMapping(value="/adddummyvalue", method = RequestMethod.GET)
    public String addUserDummy(Model model) {

        User dummyUser = new User();
        dummyUser.setDateOfBirth(new Date());
        dummyUser.setFirstName("Bikalpa");
        dummyUser.setLastName("Dhakal");
        dummyUser.setMiddleName("Raj");
        dummyUser.setNationality("Nepalese");
        dummyUser.setVisaId(22);

        userService.createUser(dummyUser);

        return "home";
    }
}

UserDaoImpl.java

package com.eversoft.traverse.daoimpl;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.springframework.stereotype.Repository;

import com.eversoft.traverse.dao.UserDao;
import com.eversoft.traverse.model.User;

@Repository
public class UserDaoImpl implements UserDao {

    static Session sessionObj;
    static SessionFactory sessionFactoryObj;

    //public final static Logger logger = Logger.getLogger(DbOperations.class);

    // This Method Is Used To Create The Hibernate's SessionFactory Object
    private static SessionFactory buildSessionFactory() {
        // Creating Configuration Instance & Passing Hibernate Configuration File
        Configuration configObj = new Configuration();
        configObj.configure("hibernate.cfg.xml");

        // Since Hibernate Version 4.x, ServiceRegistry Is Being Used
        ServiceRegistry serviceRegistryObj = new StandardServiceRegistryBuilder().applySettings(configObj.getProperties()).build(); 

        // Creating Hibernate SessionFactory Instance
        sessionFactoryObj = configObj.buildSessionFactory(serviceRegistryObj);
        return sessionFactoryObj;
    }

    @Override
    public void createUser(User user) {
        try {
            // Getting Session Object From SessionFactory
            sessionObj = buildSessionFactory().openSession();
            // Getting Transaction Object From Session Object
            sessionObj.beginTransaction();

            sessionObj.save(user);

            // Committing The Transactions To The Database
            sessionObj.getTransaction().commit();
        } catch(Exception sqlException) {
            if(null != sessionObj.getTransaction()) {
                sessionObj.getTransaction().rollback();
            }
            sqlException.printStackTrace();
        } finally {
            if(sessionObj != null) {
                sessionObj.close();
            }
        }
    }

}

UserServiceImpl.java

package com.eversoft.traverse.serviceimpl;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.eversoft.traverse.dao.UserDao;
import com.eversoft.traverse.model.User;
import com.eversoft.traverse.service.UserService;

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    UserDao userDao;

    public UserServiceImpl() {

    }

    @Override
    public void createUser(User user) {
        userDao.createUser(user);
    }

}

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>
        <!-- SQL Dialect -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Database Connection Settings -->
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/sys</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">helloworld</property>
        <property name="show_sql">true</property>

        <!-- Specifying Session Context -->
        <property name="hibernate.current_session_context_class">org.hibernate.context.internal.ThreadLocalSessionContext</property>

        <!-- <mapping class="com.eversoft.traverse.model.User" /> -->
        <!-- Mapping With Model Class Containing Annotations -->
        <!-- <mapping class="com.jcg.hibernate.crud.operations.Student" /> -->
    </session-factory>
</hibernate-configuration>

I expected a new record to be inserted to table when I hit http://localhost:8080/traverse/adddummyvalue but I get MappingException instead.

Answer 1

You need to change your code as example you referred is for Hibernate 4.3 and you are using Hibernate 5.x. Refer here for explanation.

Change your code as per hibernate 5.x docs

StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder() .configure("hibernate.cfg.xml").build();
            Metadata metadata = new MetadataSources(standardRegistry).getMetadataBuilder().build();
            return metadata.getSessionFactoryBuilder().build();