Hibernate version: 2


As per the new Hibernate In Action I implemented a HibernateFilter to utilize a request scoped transaction.

Weird issue is that it appears the filter only commits after a second request. i.e. click link 'saveStuff'
check database (nada)
click any other link
save from step 1 is commited from filter

Did I do something obvious? I did some searching and it appears the new SpringFramework version has a built in 'org.springframework.orm.hibernate.support.OpenSessionInViewFilter' which appears to be the same thing. Must I use this? OR should this be correct:



public class HibernateFilter
implements Filter {

private static final String HTTPSESSIONKEY = "HibernateSession";
private static Log log = LogFactory.getLog(HibernateFilter.class);

public void init(FilterConfig filterConfig) throws ServletException {
log.info("Servlet filter init, now disconnecting/reconnecting a Session for each request.");
}

public void doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain)
throws IOException, ServletException {
log.debug("HibernateFilter.doFilter()");
// Try to get a Hibernate Session from the HttpSession
HttpSession userSession =
((HttpServletRequest) request).getSession();
Session hibernateSession =
(Session) userSession.getAttribute(HTTPSESSIONKEY);

if (hibernateSession != null)
HibernateSession.reconnect(hibernateSession);

// If there is no Session, the first call to
// HibernateSession.beginTransaction in application code will open
// a new Session for this thread.
try {
chain.doFilter(request, response);

// Commit any pending database transaction.
HibernateSession.commitTransaction();
log.debug("Committed Transaction!");
}catch(Throwable t){
t.printStackTrace();
log.fatal("Fatal error closing transaction in filter", t);
}


finally {
// TODO: The Session should be closed if a fatal exceptions occurs

// No matter what happens, disconnect the Session.
hibernateSession = HibernateSession.disconnectSession();
log.debug("Disconnected Session!");
// and store it in the users HttpSession
userSession.setAttribute(HTTPSESSIONKEY, hibernateSession);
}
}

public void destroy() {
}

}


Along with:

<filter>
<filter-name>HibernateFilter</filter-name>
<filter-class>com.shopbotz.servlet.HibernateFilter2</filter-class>
</filter>

<filter-mapping>
<filter-name>HibernateFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>


Note: the Transaction is started in the Dao constructor as such:

public HibernateDao() {
HibernateSession.beginTransaction();
}

The stuff shown in HiA is a framework-independent way of implementing the same pattern. Spring is a framework-dependent implementation, both do the same.

P.S. You are not using the Open Session in View pattern, but the Long Session pattern with reconnect/disconnect. This is much more difficult to handle, it requires you to design the rest of your application around the "Application Transaction" concept, as explained in the book. If you reread chapter 8, you are propably looking for the "Detached Object" version and the simple Filter (both filters are in CaveatEmptor).

Christian thanks for the prompt reply.

I just discovered 'as you say' that I was biting off more than I could chew.

A simplier approach of:

try {
HibernateSession.beginTransaction();
} catch (Exception e) {
throw new ServletException("Unable to access current Hibernate session");
}
try {
chain.doFilter(request, response);
} finally {
try {
HibernateSession.commitTransaction();
HibernateSession.closeSession();
} catch (Exception e) {
}
}

works fine.

The issue was that some 'historical' code was not correctly beginning the transaction and thus no tx to commit.



Just out of curiousity how would adding the begin transaction call as below:

public void doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain)
throws IOException, ServletException {
log.debug("HibernateFilter.doFilter()");
// Try to get a Hibernate Session from the HttpSession
HttpSession userSession =
((HttpServletRequest) request).getSession();
Session hibernateSession =
(Session) userSession.getAttribute(HTTPSESSIONKEY);

if (hibernateSession != null)
HibernateSession.reconnect(hibernateSession);

// If there is no Session, the first call to
// HibernateSession.beginTransaction in application code will open
// a new Session for this thread.
try {
HibernateSession.beginTransaction(); // <--- begin transaction! ???
chain.doFilter(request, response);

// Commit any pending database transaction.
HibernateSession.commitTransaction();
log.info("Committed Transaction!");
}catch(Throwable t){
t.printStackTrace();
log.fatal("Fatal error closing transaction in filter", t);
}


finally {
// TODO: The Session should be closed if a fatal exceptions occurs

// No matter what happens, disconnect the Session.
hibernateSession = HibernateSession.disconnectSession();
log.info("Disconnected Session!");
// and store it in the users HttpSession
userSession.setAttribute(HTTPSESSIONKEY, hibernateSession);
}

Uhm, please use the "[code]" formatting element in your postings, I can't read anything.