I created a spring application where i decided to add a BaseDAO to eliminate redundant create,
update,delete,findByid,and findAll methods for every dao. So i created a baseDao and every dao should extend this BaseDAO.
BaseDaoImpl
public class BaseDAOImpl implements BaseDAO{
SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sf){
this.sessionFactory = sf;
}
#Override
public void create(ModelBase modelBase) {
Session session = this.sessionFactory.getCurrentSession();
session.persist(modelBase);
}
#Override
public void update(ModelBase modelBase) {
Session session = this.sessionFactory.getCurrentSession();
session.update(modelBase);
}
#Override
public Collection findAll(Class aClass) {
Session session = this.sessionFactory.getCurrentSession();
Collection modelCols = session.createQuery("from "+aClass.getSimpleName()).list();
return modelCols;
}
#Override
public ModelBase findById(Class aClass, Integer id) {
Session session = this.sessionFactory.getCurrentSession();
ModelBase modelBase = (ModelBase) session.load(aClass, new Integer(id));
return modelBase;
}
}
Then i extends this Dao to each DAO
EmployeeDAOImp
public class EmployeeDAOImpl extends BaseDAOImpl implements EmployeeDAO{
private SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sf){
this.sessionFactory = sf;
}
}
I created a BaseService like this. But when i try to access BaseDAO methods from EmployeeDAO it returns null pointer exception.
Why this happen. I dont want to use genericDAO from google. Because we should create DAOs
for each model. I want to eliminate this. So I follow this method.
Have you though about Spring Data project & Spring Data JPA in particular?
This would save you lots of time, since you would no longer need to write your DAO / Repositories from scratch, all you need to do is enable Spring Data JPA, and add needed interfaces. It should save you tons of time.
http://projects.spring.io/spring-data-jpa/
http://spring.io/guides/gs/accessing-data-jpa/ - Sample project
Your are overriding setSessionFactory from base class for no reason, its already available with extending class EmployeeDAOImpl , either remove it or try below:
public class EmployeeDAOImpl extends BaseDAOImpl implements EmployeeDAO{
//this reference should be from base class,
// the extending class ref is hiding base ref.
// private SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sf){
super.setSessionFactory(sf);
}
}
Something like the following should work (note the use of constructor rather than setter injection). In the BaseDAO:
public class BaseDAOImpl implements BaseDAO {
private final SessionFactory sessionFactory;
public BaseDAOImpl(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
}
Then in the Employee DAO:
public class EmployeeDAOImpl extends BaseDAOImpl implements EmployeeDAO {
#Inject
public EmployeeDAOImpl (SessionFactory sessionFactory) {
super(sessionFactory);
}
}
You can create generic dao.
#Repository("genericDao")
public class GenericDaoImpl<T,PK extends Serializable> implements GenericDao<T, PK> {
protected Class<T> entityClass;
public T create(T t) {
this.entityManager.persist(t);
return t;
}
public T read(PK id,Class<T> c) {
return (T)this.entityManager.find(c, id);
}
public T update(T t) {
return this.entityManager.merge(t);
}
public void delete(T t) {
t = this.entityManager.merge(t);
this.entityManager.remove(t);
}
public List<T> getAll(Class<T> c){
return this.entityManager.createQuery("SELECT o FROM "+ c.getName() +" o").getResultList();
}
}
UPDATED
You can use as following, TimeRange is a pojo class in the following example. If you do not want a service layer. You can use timeRangeDao in controller.
#Service("timeRangeService")
public class TimeRangeServiceImpl implements TimeRangeService{
#Autowired
GenericDao<TimeRange,Long> timeRangeDao;
public List<TimeRange> getAllTimeRanges(){
return timeRangeDao.getAll(TimeRange.class);
}
#Transactional
public void createTimeRange(TimeRange c) {
timeRangeDao.create(c);
}
#Transactional
public void update(TimeRange p) {
timeRangeDao.update(p);
}
#Transactional
public TimeRange getTimeRange(long id) {
return timeRangeDao.read(id, TimeRange.class);
}
#Transactional
public void delete(long id) {
TimeRange timeRange = new TimeRange();
timeRange.setId(id);
timeRangeDao.delete(timeRange);
}
}
Related
I am on Weblogic 12c + JPA/Hibernate + EJB 3.
I wish to simplify my class model as follow:
public abstract class AbstractEJBBean {
#PersistenceContext(unitName = "myPU")
private EntityManager entityManager;
}
#Local
public interface FirstEJB {
void someMethod1();
}
#Stateless
public class FirstEJBImpl extends AbstractEJBBean implements FirstEJB {
#Override
public void someMethod1() {
// Here entityManager has been injected.
}
}
#Local
public interface SecondEJB {
void someMethod2();
}
#Stateless
public class SecondEJBImpl extends AbstractEJBBean implements SecondEJB {
#Override
public void someMethod2() {
// Here entityManager has NOT been injected!!!
}
}
In such situation, Weblogic starts (no errors logged), the application starts, but: only then entity manager into FirstEJBImpl instance have been injected. The one inside SecondEJBImpl is null!!!
I never seen any like this.
Could somebody tell my why and how to avoid it?
Thank you so much!!!
I found the solution on my own.
I suppose it is a Weblogic bug, but I am not so sure, but my solution works as expected.
I had to remove the abstract base class and inject the entity manager directly inside each EJB.
#Local
public interface FirstEJB {
void someMethod1();
}
#Stateless
public class FirstEJBImpl implements FirstEJB {
#PersistenceContext(unitName = "myPU")
private EntityManager entityManager;
#Override
public void someMethod1() {
// Here entityManager has been injected.
}
}
#Local
public interface SecondEJB {
void someMethod2();
}
#Stateless
public class SecondEJBImpl implements SecondEJB {
#PersistenceContext(unitName = "myPU")
private EntityManager entityManager;
#Override
public void someMethod2() {
// Here entityManager has been injected too! :)
}
}
I'm trying to follow code reusing best practices.
I have generic DAO interface with some common methods:
public interface DaoInterface<T> {
T findById(int id);
//...more methods...
}
and its implementation class:
public class GenericDao<T> implements DaoInterface<T> {
#SuppressWarnings("unchecked")
private final Class<T> persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
#Autowired
protected SessionFactory sessionFactory;
#Override
#SuppressWarnings("unchecked")
public T findById(int id) {
Session session = sessionFactory.getCurrentSession();
return (T) session.get(persistentClass, id);
}
//...more methods...
}
Then my every concrete implementation class extends GenericDao and implements its interface.
I also have Service layer in my application. Some Services' methods completely delegate their work to DAO classes. So in the each concrete Service implementation I autowire appropriate DAO class and call its methods.
So now it looks:
public interface CustomerService {
Customer findById(int id);
}
and implementation:
#Service
#Transactional(readOnly = true, rollbackFor = Exception.class)
public class CustomerServiceImpl implements CustomerService {
#Autowired
private CustomerDao customerDao;
#Override
public Customer findById(int id) {
return customerDao.findById(id);
}
}
My question is - how to generify Service classes in the same way as DAO? So that my concrete class will look:
public class CustomerServiceImpl extends GenericService<Customer> implements CustomerService {
.....
}
The problem is that I cannot autowire DAO class in Generic Service:
#Autowired
private GenericDao<T> dao;
so that I could call dao's methods.
Should I do it in the constructor?
And one more question - where is the right place to annotate methods with #Transactional - in generic class or in every implementation class?
You have to create an instance of a generic Dao and put in the service layer some decision:
#Repository
public class GenericDao implements DaoInterface<T> {
//The type must be aquired at runtime,otherwise it may not be thread safe
#Autowired
protected SessionFactory sessionFactory;
#Override
#SuppressWarnings("unchecked")
public T findById(int id,Class<?> persistenceClass) {
Session session = sessionFactory.getCurrentSession();
return (T) session.get(persistenceClass, id);
}
//...more methods...
}
Also if you need a good generic repository layer take a look for Spring Data Jpa
This will make one and only one instance of the GenericDao.
Next you have 2 choice:
Create a singleton services for all your needs
Create a class service for every entity
abstract class GenericService<T> {
#Autowired
protected GenericDao dao;
#SuppressWarnings("unchecked")
protected final Class<T> persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
#Override
public T findById(int id) {
return dao.findById(id,persistenceClass);
}
}
Now every one of your service must extends the GenericService with a supplied persistence type and the job is done.
I'm implementing GenericDao. I have problem with 2 methods - getAll() and getById(Long id), entity class has null value. It looks like the class is not setted. How Can I solve this problem ?
#Repository
public class GenericDaoImpl<T> implements GenericDao<T> {
private Class<T> clazz;
#Autowired
SessionFactory sessionFactory;
public void setClazz(final Class<T> clazzToSet) {
this.clazz = clazzToSet;
}
public T getById(final Long id) {
return (T) this.getCurrentSession().get(this.clazz, id);
}
public List<T> getAll() {
Criteria criteria = sessionFactory.getCurrentSession().createCriteria(
this.clazz);
return criteria.list();
}
protected final Session getCurrentSession() {
return this.sessionFactory.getCurrentSession();
}
}
PersonDao
public interface PersonDao extends GenericDao<Person> { }
PersonDaoImpl
#Repository("PersonDAO")
public class PersonDaoImpl extends GenericDaoImpl<Person> implements PersonDao {}
Service:
#Service
public class PersonServiceImpl implements PersonService {
#Autowired
private PersonDao personDao;
#Transactional
public List<Person> getAll() {
return personDao.getAll();
}
#Transactional
public Person getById(Long id) {
return personDao.getById(id);
}
}
You must set the clazz property of PersonDao. This can be done by declaring a post initialization callback with the #PostConstruct annotation.
#Repository("PersonDAO")
public class PersonDaoImpl extends GenericDaoImpl<Person> implements PersonDao {
#PostConstruct
public void init(){
super.setClazz(Person.class);
}
}
I've been beating my head against a wall for awhile now trying to get this to work. I have created the following data access object:
public interface GenericDAO<T, ID extends Serializable> {
T findById(ID id);
List<T> findAll();
T save(T entity);
void update(T entity);
void delete(T entity);
}
public class GenericHibernateDAO<T, ID extends Serializable> implements GenericDAO<T, ID> {
private final Class<T> persistentClass;
private final SessionFactory sessionFactory;
public GenericHibernateDAO(final SessionFactory sessionFactory) {
this.persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
this.sessionFactory = sessionFactory;
}
protected Session getSession() {
return sessionFactory.getCurrentSession();
}
public Class<T> getPersistentClass() {
return persistentClass;
}
#Override
public T findById(final ID id) {
return (T) getSession().load(getPersistentClass(), id);
}
#Override #SuppressWarnings("unchecked")
public List<T> findAll() {
return findByCriteria();
}
protected List<T> findByCriteria(final Criterion... criterion) {
final Criteria crit = getSession().createCriteria(getPersistentClass());
for (final Criterion c : criterion) {
crit.add(c);
}
return crit.list();
}
#Override
public T save(final T entity) {
getSession().saveOrUpdate(entity);
return entity;
}
#Override
public void delete(final T entity) {
getSession().delete(entity);
}
#Override
public void update(final T entity) {
getSession().saveOrUpdate(entity);
}
}
#Repository
public class StockHibernateDAO extends GenericHibernateDAO<Stock, String> implements StockDAO {
#Inject
public StockHibernateDAO(final SessionFactory sessionFactory) {
super(sessionFactory);
}
}
I'm attempting to set this up with Java Configuration, so here is my configuration to setup my service layer:
#Configuration #Profile("hibernate")
#EnableCaching #EnableTransactionManagement
#ComponentScan("reference.dao.hibernate")
public class HibernateServiceConfig implements TransactionManagementConfigurer {
#Inject private StockDAO stockDao; //No extra methods, just the base stuff for now
#Bean(destroyMethod = "shutdown")
public DataSource dataSource() {
return new EmbeddedDatabaseBuilder().setType(EmbeddedDatabaseType.HSQL).addScript("classpath:schema.sql").build();
}
#Bean
public SessionFactory sessionFactory() {
return new LocalSessionFactoryBuilder(dataSource()).addAnnotatedClasses(Stock.class)
.setProperty("hibernate.show_sql", "true")
.setProperty("hibernate.cache.region.factory_class", "org.hibernate.cache.ehcache.EhCacheRegionFactory")
.setProperty("hibernate.cache.use_query_cache", "true")
.setProperty("hibernate.cache.use_second_level_cache", "true")
.setProperty("hibernate.dialect", "org.hibernate.dialect.HSQLDialect").buildSessionFactory();
}
#Override #Bean
public PlatformTransactionManager annotationDrivenTransactionManager() {
return new HibernateTransactionManager(sessionFactory());
}
}
Here is the TradingService:
#Service
public class TradingServiceImpl implements TradingService {
#Inject private StockDAO stockDAO;
#Override #Transactional
#CachePut(value = "stockCache", key = "#stock.name")
public Stock addNewStock(final Stock stock) {
stockDAO.save(stock);
return stock;
}
#Override #Cacheable(value = "stockCache")
public Stock getStock(final String stockName) {
return stockDAO.findById(stockName);
}
#Override #CacheEvict(value = "stockCache", key = "#stock.name")
public void removeStock(final Stock stock) {
stockDAO.delete(stock);
}
#Override #CacheEvict(value = "stockCache", key = "#stock.name")
public void updateStock(final Stock stock) {
stockDAO.update(stock);
}
#Override
public List<Stock> getAll() {
return stockDAO.findAll();
}
}
The saving of a stock only seems to be completed if I add a session.flush() to the save method. The way I understand things, having the TransactionManager and the #Transactional around the service layer method should in fact cause that call to be made for me. What is this configuration missing?
Because you are injecting a Session
#Bean
public Session session() {
return sessionFactory().openSession();
}
Spring cannot add it's transactional behavior around it. Let Spring open the session and do it's business.
Instead of injecting a Session, inject a SessionFactory. In your DAO, keep a attribute for SessionFactory and use sessionFactory.getCurrentSession() to acquire a session.
When Spring sees the #Transactional, it will get the SessionFactory, call openSession(), begin a transaction on it, then call your method. When your method returns successfully, it will close that transaction.
You should also probably #Autowired the dao in your service class.
I have a generic DAO class that looks like this:
public class GenericDaoJpa <T extends DomainObject> implements GenericDao<T> {
private final Class<T> type;
#PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="myPersistenceUnit")
protected EntityManager entityManager;
public GenericDaoJpa(Class<T> type) {
super();
this.type = type;
}
public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}
public T get(Object id) {
return (T) entityManager.find(type, id);
}
}
The implementation DAO class looks like this:
#Repository("appDao")
public class ProductDaoJpa extends GenericDaoJpa<Product> implements ProductDao{
public ProductDaoJpa() {
super(Product.class);
}
public List<Product> getAllProducts() {
return getAll();
}
}
I have configured another persistentUnit called mySecondPersistenceUnit for a different database. I would like to create a new DAO class that will also extend the GenericDaoJpa class but use a different persistent unit. How can i extend the GenericDaoJpa class but use a different persisitent unit for each DAO?
I tried moving this declaration to each of the DAO classes but this causes the parent class not to compile because it has no reference to the entityManager.
#PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="myPersistenceUnit")
protected EntityManager entityManager;
Try to use method injection instead:
public class GenericDaoJpa <T extends DomainObject> implements GenericDao<T> {
#PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="myPersistenceUnit")
public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}
}
While child class that need use different PU:
#Repository("appDao")
public class ProductDaoJpa extends GenericDaoJpa<Product> implements ProductDao{
#Override
#PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="mySecondPersistenceUnit")
public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}
}