EJB - JPA - Hibernate - JBoss 6-MySql - mysql

Question

I am deleveloping web project EJB,JPA - Hibernate as provider, JBoss 6,MySql.
I new in EJB, JPA.I have problems with load ejb bean in servlet.
persistence.xml
<persistence-unit name="LibraryPersistenceUnit" transaction-type="JTA">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>java:/MySqlDS</jta-data-source>
<class>library.entity.User</class>
<class>library.entity.Book</class>
<properties>
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
</properties>
</persistence-unit>
UserFacade.java
#Local
public interface UserFacade {
User findUserByLoginAndPassword(String login, String password);
/* List<User> getClients();
void returnBooks(long userId, long[] ids);
void takeBooks(long userId, long[] ids);*/
}
UserFacadeImpl.java
package library.facades.impl;
import library.dao.impl.UserDAO;
import library.entity.User;
import library.facades.interfaces.UserFacade;
import javax.ejb.EJB;
import javax.ejb.Stateless;
#Stateless
public class UserFacadeImpl implements UserFacade {
#EJB
private UserDAO userDAO;
public UserFacadeImpl() {
}
public User findUserByLoginAndPassword(String login, String password) {
User user = userDAO.selectUserByLoginAndPassword(login, password);
return user;
}
/* public List<User> getListClients() {
List<User> userList = userDAO.getClients();
return userList;
}
public void returnBooks(long userId, long[] ids) {
userDAO.returnBooks(userId, ids);
}
public void takeBooks(long userId, long[] ids) {
userDAO.takeBooks(userId, ids);
}*/
}
UserDAO.java
package library.dao.impl;
import library.dao.interfaces.GenericDAO;
import library.entity.User;
import javax.ejb.Local;
import javax.ejb.Stateless;
import java.util.HashMap;
import java.util.Map;
#Stateless
public class UserDAO extends GenericDAO {
public UserDAO() {
super(User.class);
}
public User selectUserByLoginAndPassword(String login, String password) {
Map<String, Object> parameters = new HashMap<String, Object>();
parameters.put("login", login);
parameters.put("password", password);
return (User) super.findOneResult(User.SELECT_USER_BY_LOGIN_AND_PASSWORD, parameters);
}
/*public List<User> getClients() {
Query namedQuery = entityManager.createNamedQuery(User.ALL_CLIENTS, User.class);
List<User> clientsList = namedQuery.getResultList();
return clientsList;
}
#Override
public void returnBooks(long userId, long[] ids) {
User user = entityManager.find(User.class, userId);
for (long id : ids) {
Book book = entityManager.find(Book.class, id);
user.getTakenBooks().remove(book);
}
entityManager.merge(user);
}
#Override
public void takeBooks(long userId, long[] ids) {
User user = entityManager.find(User.class, userId);
for (long id : ids) {
Book book = entityManager.find(Book.class, id);
user.getTakenBooks().add(book);
}
entityManager.merge(user);
}*/
}
GenericDAO.java
package library.dao.interfaces;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import java.util.List;
import java.util.Map;
public abstract class GenericDAO<T> {
private static final String LIBRARY_PERSISTENCE_UNIT = "LibraryPersistenceUnit";
#PersistenceContext(unitName = LIBRARY_PERSISTENCE_UNIT)
private EntityManager entityManager;
private Class<T> entityClass;
public GenericDAO() {
}
public GenericDAO(Class<T> entityClass) {
this.entityClass = entityClass;
}
public void save(T entity) {
entityManager.persist(entity);
}
protected void delete(Object id, Class<T> classe) {
T entityToBeRemoved = entityManager.getReference(classe, id);
entityManager.remove(entityToBeRemoved);
}
public T update(T entity) {
return entityManager.merge(entity);
}
public T find(int entityID) {
return entityManager.find(entityClass, entityID);
}
// Using the unchecked because JPA does not have a
// entityManager.getCriteriaBuilder().createQuery()<T> method
#SuppressWarnings({"unchecked", "rawtypes"})
public List<T> findAll() {
/* CriteriaQuery cq = entityManager.getCriteriaBuilder().createQuery();
cq.select(cq.from(entityClass));*/
return null;//entityManager.createQuery(cq).getResultList();
}
// Using the unchecked because JPA does not have a
// ery.getSingleResult()<T> method
#SuppressWarnings("unchecked")
protected T findOneResult(String namedQuery, Map<String, Object> parameters) {
T result = null;
try {
Query query = entityManager.createNamedQuery(namedQuery);
// Method that will populate parameters if they are passed not null and empty
if (parameters != null && !parameters.isEmpty()) {
populateQueryParameters(query, parameters);
}
result = (T) query.getSingleResult();
} catch (Exception e) {
System.out.println("Error while running query: " + e.getMessage());
e.printStackTrace();
}
return result;
}
private void populateQueryParameters(Query query, Map<String, Object> parameters) {
for (Map.Entry<String, Object> entry : parameters.entrySet()) {
query.setParameter(entry.getKey(), entry.getValue());
}
}
public EntityManager getEntityManager() {
return entityManager;
}
public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}
}
LibraryController
package library.controller;
import library.entity.User;
import library.facades.interfaces.UserFacade;
import library.resourses.constants.Constants;
import library.resourses.enums.Role;
import javax.ejb.EJB;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LibraryController extends HttpServlet {
#EJB
private UserFacade userFacade;
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws javax.servlet.ServletException, IOException {
performAction(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws javax.servlet.ServletException, IOException {
performAction(request, response);
}
private void performAction(HttpServletRequest request, HttpServletResponse response) {
String pageType = request.getParameter(Constants.PAGE_TYPE);
if (pageType != null) {
try {
String page = null;
String login = request.getParameter(Constants.USER_LOGIN);
String password = request.getParameter(Constants.USER_PASSWORD);
User user = userFacade.findUserByLoginAndPassword(login, password);
if (user == null) {
request.getSession().setAttribute(Constants.ERROR,
Constants.ERROR_MESSAGE_7);
page = Constants.MAIN_PAGE;
} else {
String namePage = user.getRole().toString().toLowerCase();
if (isClient(user)) {
request.getSession().setAttribute(Constants.CLIENT,
user);
request.getSession().setAttribute(Constants.ERROR, null);
} else if (isAdministrator(user)) {
request.getSession().setAttribute(Constants.ADMINISTRATOR,
user);
request.getSession().setAttribute(Constants.ERROR, null);
}
page = Constants.START_PAGES + namePage + Constants.END_PAGES;
}
RequestDispatcher requestDispatcher = getServletContext().getRequestDispatcher(page);
requestDispatcher.forward(request, response);
} catch (ServletException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private boolean isAdministrator(User user) {
return user.getRole().equals(Role.ADMINISTRATOR);
}
private boolean isClient(User user) {
return user.getRole().equals(Role.CLIENT);
}
}
I get null for userFacade.Can you explain me what I do wrong.
Thanks.

Answer 1

The problem is that instead of letting the container instantiate and inject the DAO for you, you explicitely create the DAO instance by yourself:
private IUserDAO dao;
public UserService() {
dao = UserDAOImpl.getInstance();
}
For the EntityManager to be injected into the DAO, the container must instantiate it, not you. Replace the above code with the following, which uses dependency injection, and will thus also have the advantage of making your code testable:
#Inject
private IUserDAO dao;