Hibernate 5 :- org.hibernate.MappingException: Unknown entity

Question

I am getting the error message org.hibernate.MappingException: Unknown entity when i am trying to integrate hibernate 5.0 with mysql

This seems to be an issue with hibernate5.0.0 and 5.0.1 . This works fine with hibernate 4.3.9

Maven dependices

<dependency>
    <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.0.0.Final</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.36</version>
</dependency>

hibernate.cfg.xml

<session-factory>

    <!-- Database connection settings -->
    <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="connection.url">jdbc:mysql://localhost:3307/SampleDB
    </property>
    <property name="connection.username">root</property>
    <property name="connection.password"></property>

    <!-- JDBC connection pool (use the built-in) -->
    <property name="connection.pool_size">1</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">true</property>

    <!-- Drop and re-create the database schema on startup -->
    <property name="hbm2ddl.auto">create</property>

    <mapping class="UserA.User"></mapping>

</session-factory>

HibernateMain.java code

package UserA;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.mapping.Map;
import org.hibernate.metadata.ClassMetadata;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.service.ServiceRegistry;

public class HibernateMain {

    public static void main(String[] args) {

        Configuration configuration = new Configuration();
        configuration.configure();
        ServiceRegistry sr = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();

        SessionFactory sf = configuration.buildSessionFactory(sr);




        User user1 = new User();
        user1.setUserName("Arpit");
        user1.setUserMessage("Hello world from arpit");
        user1.setUserId(22);

        Session ss = sf.openSession();
        ss.beginTransaction();
        // saving objects to session
        ss.save(user1);
        ss.getTransaction().commit();
        ss.close();

    }

}

User.java

package UserA;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;

@Entity(name="User_table")
public class User {
    @Id
    int userId;
    @Column(name = "User_Name")
    String userName;

    @Column(name = "User_Message")
    String userMessage;

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserMessage() {
        return userMessage;
    }

    public void setUserMessage(String userMessage) {
        this.userMessage = userMessage;
    }

}

Answer 1

I have fixed the same issue with Hibernate 5. There is a problem in this code

Configuration configuration = new Configuration();
configuration.configure();

ServiceRegistry sr = new StandardServiceRegistryBuilder().applySettings(
    configuration.getProperties()).build();

SessionFactory sf = configuration.buildSessionFactory(sr);

This code works fine for Hibernate 4.3.5, but the same code has the same issue for Hibernate 5.

When you do configuration.buildSessionFactory(sr) , using Hibernate 5, Configuration losts all information about mapping that gets by call configuration.configure() .

Solution

To fix the issue, if you use standard configuration files hibernate.cfg.xml and hibernate.properties , you can create the session factory by this way (without ServiceRegistry )

SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

Loading properties

If you have properties in a file other then hibernate.properties , you can build session factory using StandardServiceRegistryBuilder (anyway, if you have hibernate.properties and other file, it will be loaded both)

To load properties as a resource

ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().
    configure().loadProperties("hibernate-h2.properties").build();
SessionFactory sf = new Configuration().buildSessionFactory(serviceRegistry);  

You need to have hibernate-h2.properties in the class path (root of the sources folder, resources folder). You can specify a path from the root source folder too /com/github/xxx/model/hibernate-h2.properties .

To load properties from a path in the file system

File propertiesPath = new File("some_path");
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().
    configure().loadProperties(propertiesPath).build();
SessionFactory sf = new Configuration().buildSessionFactory(serviceRegistry);

You can find an example console application using this approach here fluent-hibernate-mysql . It uses a utility class to build the session factory from the fluent-hibernate library .

Incorrect Hibernate 5 tutorial

There is an incorrect example in Hibernate 5 tutorial 1.1.6. Startup and helpers . It uses this code

 return new Configuration().configure().buildSessionFactory(
                new StandardServiceRegistryBuilder().build() );

It doesn't do a proper configuration.

Answer 2

In Hibernate 5, you need to build StandardServiceRegistry and Metadata to build SessionFactory . You could use the following HibernateUtil to build SessionFactory . hibernate.cfg.xml should be in the root of the classpath of your application.

public class HibernateUtil {

    private static final SessionFactory sessionFactory = buildSessionFactory();

    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder() .configure("hibernate.cfg.xml").build();
            Metadata metadata = new MetadataSources(standardRegistry).getMetadataBuilder().build();
            return metadata.getSessionFactoryBuilder().build();
        } 
        catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

}

Also, If you're using Hibernate 5 and using @Id as your identifier generation strategy then using GenerationType.AUTO will pick up the "sequence" identity generator by default with MySQL, which will give you an the com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'SampleDB.hibernate_sequence' doesn't exist exception, if you don't have it configured in your entities at identifier attributes. So with Hibernate 5, use GenerationType.IDENTITY instead.

Answer 3

您没有添加配置文件

configuration.configure("/hibernate.cfg.xml");

Answer 4

请确保您已创建映射文件User.hbm.xml或User.xml文件，并将该文件包含在hibernate.cfg.xml中

Answer 5

Using this:

SessionFactory sessionFactory = entityManagerFactory.unwrap(SessionFactory.class);

Session session = sessionFactory.openSession();

instead of this:

SessionFactory factory = new Configuration().configure().buildSessionFactory();

Session session = factory.openSession();

solved the issue with Hibernate 5.2.10.Final.

Answer 6

I was facing the same issue & I searched for almost 2 hours and tried with different possible ways like replacing old hibernate jars&changing the db table schema. But finally got the solution as below;

 //This line to be replaced with below commented line
 SessionFactory factory = new Configuration().configure().buildSessionFactory();

Replace above for

Configuration config = new Configuration().configure();
ServiceRegistry servReg = new StandardServiceRegistryBuilder().applySettings(config.getProperties()).build();
SessionFactory factory = config.buildSessionFactory(servReg);

It will then work fine..