第五章Hibernate-OSIV与泛型DAO方式

第五章Hibernate-OSIV与泛型DAO模式

第五章Hibernate-OSIV与泛型DAO模式

??????? 使用Servlet过滤器实现OSIV模式

??????????? 1.编写泛型DAO接口

??????????? 2.编写泛型DAO的实现类

??????????? 3.使用GenericDao接口

??????????? 4.使用GenericDaoHibernate类

????? 我们使用servlet过滤器来实现自己的OSIV模式。当用户向一个JSP页面或者Servlet发出请求的时候开启Session对象，在JSP页面或者Servlet执行之后，在关闭Session对象。

??? 编写HibernateSessionFilter.java

public class HibernateSessionFilter implements Filter {private Transaction transaction = null;    private SessionFactory sessionFactory = null;public void destroy() {sessionFactory.close();}public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {try{Session session = sessionFactory.getCurrentSession();  transaction = session.beginTransaction(); chain.doFilter(request, response); transaction.commit();}catch(Exception e){e.printStackTrace();try{if(transaction.isActive()){transaction.rollback();}} catch(Exception e2){e2.printStackTrace();}}}public void init(FilterConfig arg0) throws ServletException {sessionFactory = new Configuration().configure().buildSessionFactory();}}

?? 配置web.xml

<filter><filter-name>HibernateSessionFilter</filter-name><filter-class>com.crazy.HibernateSessionFilter</filter-class></filter><filter-mapping><filter-name>HibernateSessionFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>

????? 1 编写泛型DAO接口

????? 2 编写泛型DAO的实现类

????? 3 GenericDao.java

????? 4 GenericDaoHibernate.java

public interface GenericDao<T,PK extends Serializable> {public T findById(PK id);public List<T> findAll();public T save(T entity);public void update(T entity);public void delete(T entity);}

public class GenericDaoHibernate<T, PK extends Serializable> implements GenericDao<T,PK> {private Class<T> clazz;public GenericDaoHibernate(){clazz = (Class<T>)((ParameterizedType)getClass().getGenericSuperclass()).getActualTypeArguments()[0];}public void delete(T entity) {Session session = new Configuration().configure().buildSessionFactory().openSession();session.delete(entity);}public List findAll() {Session session = new Configuration().configure().buildSessionFactory().openSession();Query query = session.createQuery("from" +clazz.getName());return query.list();}public T findById(PK id) {Session session = new Configuration().configure().buildSessionFactory().openSession();return (T)session.get(clazz, id);}public T save(T entity) {Session session = new Configuration().configure().buildSessionFactory().openSession();session.save(entity);return entity;}public void update(T entity) {Session session = new Configuration().configure().buildSessionFactory().openSession();session.update(entity);}}

?由于Java中的泛型采用擦拭方法，因此无法直接通过反射获取到T.class。而getGenericSuperclass()方法会返回一个ParameterizedType对象，这个对象保存负累的泛型绑定参数的类型，所以通过该对象即可获取T.class。

public interface GuestbookDao extends GenericDao <Guestbook,Integer> {public List<Guestbook> findAllOrderById();}

public class GuestbookDaoHibernate extends GenericDaoHibernate<Guestbook,Integer> implements GuestbookDao{public List<Guestbook> findAllOrderById() {Session session = new Configuration().configure().buildSessionFactory().openSession();Query query = session.createQuery("from Guestbook order by id desc");return query.list();}}

?