Why we are getting currentsession twice in the application?
Recently I did some work around to check, where to give the session related code in our application, ie .Getting current session (sessionFactory.getCurrentSession());
I have seen this code in place twice in the application, one in HibernateSessionRequestFileter Class
package com.persistence;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.SessionFactory;
import org.hibernate.StaleObjectStateException;
public class HibernateSessionRequestFilter implements Filter {
private static Log log = LogFactory.getLog(HibernateSessionRequestFilter.class);
private SessionFactory sf;
public void doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain)
throws IOException, ServletException {
try {
log.debug("Starting a database transaction");
sf.getCurrentSession().beginTransaction();
// Call the next filter (continue request processing)
chain.doFilter(request, response);
// Commit and cleanup
log.debug("Committing the database transaction");
sf.getCurrentSession().getTransaction().commit();
} catch (StaleObjectStateException staleEx) {
log.error("This interceptor does not implement optimistic concurrency control!");
log.error("Your application will not work until you add compensation actions!");
// Rollback, close everything, possibly compensate for any permanent changes
// during the conversation, and finally restart business conversation. Maybe
// give the user of the application a chance to merge some of his work with
// fresh data... what you do here depends on your applications design.
throw staleEx;
} catch (Throwable ex) {
// Rollback only
ex.printStackTrace();
try {
if (sf.getCurrentSession().getTransaction().isActive()) {
log.debug("Trying to rollback database transaction after exception");
//sf.getCurrentSession().getTransaction().rollback();
}
} catch (Throwable rbEx) {
log.error("Could not rollback transaction after exception!", rbEx);
}
开发者_Go百科 // Let others handle it... maybe another interceptor for exceptions?
throw new ServletException(ex);
}
}
public void init(FilterConfig filterConfig) throws ServletException {
log.debug("Initializing filter...");
log.debug("Obtaining SessionFactory from static HibernateUtil singleton");
sf = HibernateUtil.getSessionFactory();
}
public void destroy() {}
}
Another one in GenericHibernateDAO Class Like below,
protected Session getSession() {
if (session == null) {
session = HibernateUtil.getSessionFactory().getCurrentSession();
} else if (!session.isConnected()) {
session = HibernateUtil.getSessionFactory().getCurrentSession();
}
return session;
}
Can anybody help me to understand, why we have to get currentsession in two places? While we begin the transaction, we are getting the currentsession , same as while we persist or getting object from database, again we are getting the currentsession, why is it so?
This looks like a version of an OpenSessionInView pattern, where a Hibernate Session is opened when a request is received and closed after the response is rendered.
In the filter a session is opened and a transaction is started.
Then the request is processed and in the Dao the call to getCurrentSession()
only get's the current open session, it isn't creating a new Session.
The dao does its work. Then the filter commits the transaction and the session is closed.
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