Using Dynamic Proxies to centralize JPA code
- by Daziplqa
Hi All,
Actually, This is not a question but really I need your opinions in a matter...
I put his post here because I know you always active, so please don't consider this a bad question and share me your opinions.
I've used Java dynamic proxies to Centralize The code of JPA that I used in a standalone mode, and Here's the dynamic proxy code:
package com.forat.service;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import com.forat.service.exceptions.DAOException;
/**
* Example of usage :
* <pre>
* OnlineFromService onfromService =
* (OnlineFromService) DAOProxy.newInstance(new OnlineFormServiceImpl());
* try {
* Student s = new Student();
* s.setName("Mohammed");
* s.setNationalNumber("123456");
* onfromService.addStudent(s);
* }catch (Exception ex) {
* System.out.println(ex.getMessage());
* }
*</pre>
* @author mohammed hewedy
*
*/
public class DAOProxy implements InvocationHandler{
private Object object;
private Logger logger = Logger.getLogger(this.getClass().getSimpleName());
private DAOProxy(Object object) {
this.object = object;
}
public static Object newInstance(Object object) {
return Proxy.newProxyInstance(object.getClass().getClassLoader(),
object.getClass().getInterfaces(), new DAOProxy(object));
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
EntityManagerFactory emf = null;
EntityManager em = null;
EntityTransaction et = null;
Object result = null;
try {
emf = Persistence.createEntityManagerFactory(Constants.UNIT_NAME);
em = emf.createEntityManager();;
Method entityManagerSetter = object.getClass().
getDeclaredMethod(Constants.ENTITY_MANAGER_SETTER_METHOD, EntityManager.class);
entityManagerSetter.invoke(object, em);
et = em.getTransaction();
et.begin();
result = method.invoke(object, args);
et.commit();
return result;
}catch (Exception ex) {
et.rollback();
Throwable cause = ex.getCause();
logger.log(Level.SEVERE, cause.getMessage());
if (cause instanceof DAOException)
throw new DAOException(cause.getMessage(), cause);
else
throw new RuntimeException(cause.getMessage(), cause);
}finally {
em.close();
emf.close();
}
}
}
And here's the link that contains more info (http://m-hewedy.blogspot.com/2010/04/using-dynamic-proxies-to-centralize-jpa.html) (plz don't consider this as adds, as I can copy and past the entire topic here if you want that)
So, Please give me your opinions.
Thanks.
