Ciao, grazie ok proviamo...

questa è la persistence:
codice:
<?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/persisten...stence_2_0.xsd">
  <persistence-unit name="StockManagerPU" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>Entity.Shanghai</class>
    <class>Entity.Nikkei</class>
    <class>Entity.Seoul</class>
    <class>Entity.Hang_Seng</class>
    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:mysql://127.0.0.1:3306/mydb"/>
      <property name="javax.persistence.jdbc.password" value=""/>
      <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
      <property name="javax.persistence.jdbc.user" value="root"/>
      <property name="eclipselink.ddl-generation" value="create-tables"/>
    </properties>
  </persistence-unit>
</persistence>
le colonne del db sono:

OPE double; CLOS double; MI double; MA double; VOLU double; DAT varchar(15);

le entity sono così:
codice:
package Entity;
import javax.persistence.*;

/**
 *
 * @author DARIO
 */

@Entity
public class Nikkei {
    @Id
    private String DAT;
    private Double OPE;
    private Double CLOS;
    private Double MI;
    private Double MA;
    private Double VOLU;

    /**
     * @return the DAT
     */
    public String getDAT() {
        return DAT;
    }

    /**
     * @param DAT the DAT to set
     */
    public void setDAT(String DAT) {
        this.DAT = DAT;
    }

    /**
     * @return the OPE
     */
    public Double getOPE() {
        return OPE;
    }

    /**
     * @param OPE the OPE to set
     */
    public void setOPE(Double OPE) {
        this.OPE = OPE;
    }

    /**
     * @return the CLOS
     */
    public Double getCLOS() {
        return CLOS;
    }

    /**
     * @param CLOS the CLOS to set
     */
    public void setCLOS(Double CLOS) {
        this.CLOS = CLOS;
    }

    /**
     * @return the MI
     */
    public Double getMI() {
        return MI;
    }

    /**
     * @param MI the MI to set
     */
    public void setMI(Double MI) {
        this.MI = MI;
    }

    /**
     * @return the MA
     */
    public Double getMA() {
        return MA;
    }

    /**
     * @param MA the MA to set
     */
    public void setMA(Double MA) {
        this.MA = MA;
    }

    /**
     * @return the VOLU
     */
    public Double getVOLU() {
        return VOLU;
    }

    /**
     * @param VOLU the VOLU to set
     */
    public void setVOLU(Double VOLU) {
        this.VOLU = VOLU;
    }
    public String toString() {
    return "Data id: " + getDAT() + " Open: " + getOPE() + " Close: " + getCLOS()+" Mi: " + getMI() +" Ma: " + getMA()+" Volum: " + getVOLU();

   }

}
Grazie Mille per la pazienza ciao!!!