持久性单元异常

Question

我的Enterprise Java Bean存在这个问题。 日志文件： stack trace

我不知道如何解决它！这是我的实体类：

$new = array();

$c = 1;

for($i=0;$i<count($a);$i++)
{
    $sum =0;

    for($k=0;$k<count($a[$i]);$k++)
    {
        $sum = $sum + $a[$i][$k]['buysell'];

    }
    $new[$i]['buysell'] = $sum;

    $new[$i]['extracthour'] = $c;

    $c++;
}

echo "<pre>";
print_r($new);

这是我的EJB：

Array
(
    [0] => Array
        (
            [buysell] => 7350
            [extracthour] => 1
        )

    [1] => Array
        (
            [buysell] => 480
            [extracthour] => 2
        )

)

这是我的persistence.xml：

package entities;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;


    /**
     *
     * @author gfucc
     */
    @Entity
    @NamedQueries({
        @NamedQuery(name = "Student.findAll", query = "SELECT s FROM Students"),
        @NamedQuery(name = "Student.findByMatr", query = "SELECT s FROM Student s WHERE s.matricola = :matricola"),
        @NamedQuery(name = "Student.findByCognome", query = "SELECT s FROM Student s WHERE s.cognome = :cognome")
    })
    public class Student 
    {
        @Id @GeneratedValue
        private String matricola;

        @NotNull
        @Column(length = 100)
        private String nome;

        @NotNull
        @Column(length = 100)
        private String cognome;

        @NotNull
        @Column(length = 100)
        private String corsoLaurea;

        @NotNull
        @Size(min = 0, max = 30)
        private int numEsamiSostenuti;

        public Student()
        {

        }

        public Student(String nome, String cognome, String corsoLaurea, int numEsamiSostenuti) {
            this.nome = nome;
            this.cognome = cognome;
            this.corsoLaurea = corsoLaurea;
            this.numEsamiSostenuti = numEsamiSostenuti;
        }

        public String getMatricola() {
            return matricola;
        }

        public void setMatricola(String matricola) {
            this.matricola = matricola;
        }

        public String getNome() {
            return nome;
        }

        public void setNome(String nome) {
            this.nome = nome;
        }

        public String getCognome() {
            return cognome;
        }

        public void setCognome(String cognome) {
            this.cognome = cognome;
        }

        public String getCorsoLaurea() {
            return corsoLaurea;
        }

        public void setCorsoLaurea(String corsoLaurea) {
            this.corsoLaurea = corsoLaurea;
        }

        public int getNumEsamiSostenuti() {
            return numEsamiSostenuti;
        }

        public void setNumEsamiSostenuti(int numEsamiSostenuti) {
            this.numEsamiSostenuti = numEsamiSostenuti;
        }

        @Override
        public String toString() {
            return "Student{" + 
                    "matricola=" + matricola + 
                    ", nome=" + nome + 
                    ", cognome=" + cognome + 
                    ", corsoLaurea=" + corsoLaurea + 
                    ", numEsamiSostenuti=" + numEsamiSostenuti + '}';
        } 
    }

这是我的beans.xml：

package ejbs;

import entities.Student;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;
import qualifiers.Loggable;

/**
 *
 * @author gfucc
 */
@Stateless
@Loggable
public class StudentEJB implements StudentEJBRemote 
{
    @PersistenceContext(unitName = "StudentEJBPU")
    private EntityManager em;

    @Override
    public Student createStudent(Student student)
    {
        em.persist(student);
        return this.getStudentByMatricola(student.getMatricola());

    }

    @Override
    public Student removeStudent(Student student) 
    {
        Student toReturn = this.getStudentByMatricola(student.getMatricola());
        if(toReturn != null)
        {
            em.remove(student);
            return toReturn;
        }
        return null;

    }

    @Override
    public Student updateStudent(Student student) 
    {
        return em.merge(student);
    }

    @Override
    public List<Student> getStudentList() 
    {
        TypedQuery<Student> query = em.createNamedQuery("Student.findAll", Student.class);
        return query.getResultList();
    }

    @Override
    public Student getStudentByMatricola(String matricola) 
    {
        TypedQuery<Student> query = em.createNamedQuery("Student.findByMatr", Student.class);
        query.setParameter(1, matricola);
        return query.getSingleResult();
    }

    @Override
    public Student getStudentByCognome(String cognome) 
    {
        TypedQuery<Student> query = em.createNamedQuery("Student.findByCognome", Student.class);
        query.setParameter(1, cognome);
        return query.getSingleResult();
    }


}

现在，在这些图片中，您可以看到我的项目结构： project structure

有什么问题？我都是。我连接的数据库，我使用默认数据库“示例”...问题是在持久性单元上，因为没有它我可以构建，然后部署没有问题！请帮忙。非常感谢