persist() null pointer exception

[Alan Smith]

Hi,

I have yet been able to insert a record into a table using the Entitymanager. Everytime I use the persist method I get a null pointer exception. I have a person entity with id(auto incrememted), name, job, salary,description, countyId(foreign key) in a MySql table call Person. My servlet creates a Manager class and passes in parameters submitted representing Person information.

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String userPath = request.getServletPath();
        County selectedCounty;

        if (userPath.equals("/addUser")) {
            String name = request.getParameter("name");
            String job = request.getParameter("job");
            String salary = request.getParameter("salary");
            String description = request.getParameter("description");
            String county = request.getParameter("county");

            request.setAttribute("name", name);
            request.setAttribute("job", job);
            request.setAttribute("salary", salary);
            request.setAttribute("description", description);
            request.setAttribute("county", county);

            selectedCounty = countyFacade.find(Integer.parseInt(county));
            Manager manager = new Manager();
            manager.addPerson(name, job, salary, description, selectedCounty);
        }

        String url = "/WEB-INF/view" + userPath + ".jsp";

        try {
            request.getRequestDispatcher(url).forward(request, response);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

The manager class looks like this:

import entity.County;
import entity.Person;
import javax.ejb.EJB;
import javax.ejb.LocalBean;
import javax.ejb.Stateless;
import session.PersonFacade;

/**
 *
 * @author esmiala
 */
@Stateless
@LocalBean
public class Manager {

    @EJB
    private session.PersonFacade pf;

    public void addPerson(String name, String job, String salary, String description, County selectedCounty) {   
        
        Person p = new Person();
        p.setName(name);
        p.setJob(job);
        p.setSalary(salary);
        p.setDescription(description);
        p.setCountyId(selectedCounty);
        
        pf = new PersonFacade();
        
        pf.create(p);
    }
}

The PersonFacade class i am using is a netbeans generated session bean:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package session;

import entity.Person;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

/**
 *
 * @author esmiala
 */
@Stateless
public class PersonFacade extends AbstractFacade<Person> {
    @PersistenceContext(unitName = "IrelandPU")
    private EntityManager em;

    @Override
    protected EntityManager getEntityManager() {
        return em;
    }

    public PersonFacade() {
        super(Person.class);
    }
    
}

and AbstractFacade is as follows:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package session;

import java.util.List;
import javax.persistence.EntityManager;

/**
 *
 * @author esmiala
 */
public abstract class AbstractFacade<T> {
    private Class<T> entityClass;

    public AbstractFacade(Class<T> entityClass) {
        this.entityClass = entityClass;
    }

    protected abstract EntityManager getEntityManager();

    public void create(T entity) {
        getEntityManager().persist(entity);
    }

    public void edit(T entity) {
        getEntityManager().merge(entity);
    }

    public void remove(T entity) {
        getEntityManager().remove(getEntityManager().merge(entity));
    }

    public T find(Object id) {
        return getEntityManager().find(entityClass, id);
    }

    public List<T> findAll() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        return getEntityManager().createQuery(cq).getResultList();
    }

    public List<T> findRange(int[] range) {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        q.setMaxResults(range[1] - range[0]);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }

    public int count() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
        cq.select(getEntityManager().getCriteriaBuilder().count(rt));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        return ((Long) q.getSingleResult()).intValue();
    }
    
}

edit: Person entity class

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package entity;

import java.io.Serializable;
import javax.persistence.*;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;

/**
 *
 * @author esmiala
 */
@Entity
@Table(name = "person")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Person.findAll", query = "SELECT p FROM Person p"),
    @NamedQuery(name = "Person.findById", query = "SELECT p FROM Person p WHERE p.id = :id"),
    @NamedQuery(name = "Person.findByName", query = "SELECT p FROM Person p WHERE p.name = :name"),
    @NamedQuery(name = "Person.findByJob", query = "SELECT p FROM Person p WHERE p.job = :job"),
    @NamedQuery(name = "Person.findBySalary", query = "SELECT p FROM Person p WHERE p.salary = :salary")})
public class Person implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @NotNull
    @Column(name = "id")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "name")
    private String name;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "job")
    private String job;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "salary")
    private String salary;
    @Basic(optional = false)
    @NotNull
    @Lob
    @Size(min = 1, max = 65535)
    @Column(name = "description")
    private String description;
    @JoinColumn(name = "county_id", referencedColumnName = "id")
    @ManyToOne(optional = false)
    private County countyId;

    public Person() {
    }

    public Person(Integer id) {
        this.id = id;
    }

    public Person(Integer id, String name, String job, String salary, String description) {
        this.id = id;
        this.name = name;
        this.job = job;
        this.salary = salary;
        this.description = description;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }

    public String getSalary() {
        return salary;
    }

    public void setSalary(String salary) {
        this.salary = salary;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public County getCountyId() {
        return countyId;
    }

    public void setCountyId(County countyId) {
        this.countyId = countyId;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Person)) {
            return false;
        }
        Person other = (Person) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "entity.Person[ id=" + id + " ]";
    }
    
}

I can read person entries from the database using the personFacades findAll() method but I can't write to it using the create() method without a null pointer exception showing up. All the objects I use are not pointing to a null reference so I can't get my head around it! I have seen examples all over the net that use the persist method. Could someone please help?

Thanks

[James Sutherland]

Please include the exception stack trace.