JPA With Hibernate Error: [PersistenceUnit: JPA] Unable to build EntityManagerFactory

Question

I have a problem with Java Persistence API and Hibernate. My situation of project is:

My persistence.xml file is:

<persistence 
    xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <persistence-unit name="JPA">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <class>com.david.Libro</class>
        <class>com.david.Categoria</class>
        <properties>
            <property name="hibernate.show_sql" value="true" />
            <property name="javax.persistence.transactionType" value="RESOURCE_LOCAL" />
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/arquitecturaJava" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="root" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
        </properties>
    </persistence-unit>
</persistence>

And i create EntityManagerFactory in:

private static EntityManagerFactory buildEntityManagerFactory() 
    {
        try 
        {
            return Persistence.createEntityManagerFactory("JPA");
        } 
        catch (Throwable ex) 
        {
                    ex.printStackTrace();
            //throw new RuntimeException("Error al crear la factoria de JPA:->"+ ex.getMessage());
        }
    }

My error is about create EntityManagerFactory:

    javax.persistence.PersistenceException: [PersistenceUnit: JPA] Unable to build EntityManagerFactory
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:924)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:899)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:59)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
    at com.david.JPAHelper.buildEntityManagerFactory(JPAHelper.java:14)
    at com.david.JPAHelper.<clinit>(JPAHelper.java:8)
    at com.david.Categoria.buscarTodos(Categoria.java:93)
    at com.david.FormularioInsertarLibroAccion.ejecutar(FormularioInsertarLibroAccion.java:25)
    at com.david.ControladorLibros.doGet(ControladorLibros.java:38)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: org.hibernate.DuplicateMappingException: Duplicate class/entity mapping com.david.Libro
    at org.hibernate.cfg.Configuration$MappingsImpl.addClass(Configuration.java:2638)
    at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:706)
    at org.hibernate.cfg.Configuration$MetadataSourceQueue.processAnnotatedClassesQueue(Configuration.java:3512)
    at org.hibernate.cfg.Configuration$MetadataSourceQueue.processMetadata(Configuration.java:3466)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1355)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1756)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:96)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:914)
    ... 27 more

Part of Libro and Categoria classes code is:

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

    @Id
    @JoinColumn(name = "categoria") 
    private String id;
    private String descripcion;

....

and

@Entity
@Table(name="Libros")
public class Libro implements Serializable
{
    private static final long serialVersionUID = 1L;
    
    @Id
    private String isbn;
    private String titulo;
    @ManyToOne
    @JoinColumn (name="categoria")
    private Categoria categoria;

....

My file of Hibernate Configuration is:

<?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="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost/arquitecturajava</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.pool_size">5</property>
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <property name="show_sql">true</property>
        
        <mapping class="com.david.Categoria"></mapping>
        <mapping class="com.david.Libro"></mapping>
        
    </session-factory>
</hibernate-configuration>

Any ideas!! Thank´s!!

Answer 1

You don't need both hibernate.cfg.xml and persistence.xml in this case. Have you tried removing hibernate.cfg.xml and mapping everything in persistence.xml only?

But as the other answer also pointed out, this is not okay like this:

@Id
@JoinColumn(name = "categoria") 
private String id;

Didn't you want to use @Column instead?