Save same object multiple times

Solution: setar id = null

The code saves 10 times if it runs on the Tomcat server, but if it runs on Glassfish it only adds one time.

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
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">
<persistence-unit name="default" transaction-type="RESOURCE_LOCAL">
    <class>entities.Secao</class>
    <class>entities.Funcionario</class>
    <class>entities.Unidade</class>
    <class>entities.Patrimonio</class>
    <class>entities.Descricao</class>
    <class>entities.Classificacao</class>

    <validation-mode>AUTO</validation-mode>
    <properties>
        <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/patrimonio" />
        <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
        <property name="javax.persistence.jdbc.user" value="root" />
        <property name="javax.persistence.jdbc.password" value="root" />
        <property name="hibernate.hbm2ddl.auto" value="update" />
        <property name="hibernate.show_sql" value="true" />
        <property name="hibernate.format_sql" value="true" />
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />

    </properties>
</persistence-unit>

public void save() {
    int i = 0;
    EntityManager em = JpaUtil.getEntityManager();

    while (i < 10) {
        em.merge(item);         
        i = i + 1;          
    }
    item = new Item();      
}

JPAUtil class:

package persistence;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

import org.hibernate.Session;

public class JpaUtil {

    private static final String PERSISTENCE_UNIT_NAME = "default";

    private static ThreadLocal<EntityManager> manager = new ThreadLocal<EntityManager>();

    private static EntityManagerFactory factory;

    private JpaUtil() {
    }

    public static boolean isEntityManagerOpen() {
        return JpaUtil.manager.get() != null && JpaUtil.manager.get().isOpen();
    }

    public static EntityManager getEntityManager() {
        if (JpaUtil.factory == null) {
            JpaUtil.factory = Persistence
                    .createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
        }
        EntityManager em = JpaUtil.manager.get();
        if (em == null || !em.isOpen()) {
            em = JpaUtil.factory.createEntityManager();
            JpaUtil.manager.set(em);
        }
        return em;
    }

    public static void evictCache(EntityManager em, String region) {
        ((Session) em.getDelegate()).getSessionFactory().getCache()
                .evictQueryRegion(region);
    }

    public static void closeEntityManager() {
        EntityManager em = JpaUtil.manager.get();
        if (em != null) {
            EntityTransaction tx = em.getTransaction();
            if (tx.isActive()) {
                tx.commit();
            }
            em.close();
            JpaUtil.manager.set(null);
        }
    }

    public static void closeEntityManagerFactory() {
        closeEntityManager();
        JpaUtil.factory.close();
    }
}