(hibernate4) org.hibernate.MappingException: Unknown entity

问题

I am a newbie to Java EE, please help!

The following code used struts2+hibernate4+oracle11g. After I run this code, it gives me this error message:

org.hibernate.MappingException: Unknown entity

UserDetails.java

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

@Entity
@Table(name="users")
public class UserDetails {
    @Id
    private int id;
    private String passwd;
    public String getPasswd() {
        return passwd;
    }
    public void setPasswd(String passwd) {
        this.passwd = passwd;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }

    public void Update(){
        SessionFactory sessionFactory;
        ServiceRegistry serviceRegistry;

        Configuration configuration = new Configuration();
        configuration.configure();
        serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();        
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);

        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save(this);
        session.getTransaction().commit();
    }
}

hibernate.cfg.xml

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

  <session-factory>

    <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
    <property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
    <property name="connection.url">jdbc:oracle:thin:@192.168.1.2:1521:orcl</property>
    <property name="connection.username">steve</property>
    <property name="connection.password">steve</property>

    <property name="cache.provider_class">org.hibernate.cache.HashtableCacheProvider</property>

    <property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
    <property name="current_session_context_class">thread</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hbm2ddl.auto">create</property>
  </session-factory>

</hibernate-configuration>

Table Structure:

Create table Users (ID int primary key, passwd varchar(45));

回答1:

You need to add the class:

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

@Entity
@Table(name="users")
public class UserDetails {
    @Id
    private int id;
    private String passwd;
    public String getPasswd() {
        return passwd;
    }
    public void setPasswd(String passwd) {
        this.passwd = passwd;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }

    public void Update(){
        SessionFactory sessionFactory;
        ServiceRegistry serviceRegistry;

        Configuration configuration = new Configuration();
        configuration.addAnnotatedClass(UserDetails.class); //<-- Here, adds the class to the Hibernate configuration
        configuration.configure();
        serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();        
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);

        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save(this);
        session.getTransaction().commit();
    }
}

You definitely do not want to construct a new Hibernate Configuration and SessionFactory each time you want to save something to the table, so move the stuff from Update to an init method somewhere.

回答2:

The problem is that you haven't defined your class to hiberante.

Inside your session-factory add these lines:

<property name="annotatedClasses">
    <list>
        <value>myPackage.UserDetails</value>
    </list>
</property>

回答3:

Hibernate mapping for entity is missing. Alternatively you can use in your hibernate configuration file. and define the UserDetails.hbm.xml. I hope this will be helpfull.

来源：https://stackoverflow.com/questions/13913022/hibernate4-org-hibernate-mappingexception-unknown-entity