Re: back button, deserialisation and readObject()

[Steve Swinsburg]

Thanks Martijn,





cheers,
Steve





On 2 Apr 2009, at 12:22, Martijn Dashorst wrote:

Understand re logger and making it a static instance, but what about other transient fields, is it ok to override getObject on each page an re setup my transient fields or is this going to cause issues down the track?

magic word for loggers: static

and your assumption is correct: if you don't do anything, you'll get
NPE's when you reference a transient field on an object that has been
deserialized.

Martijn

On Thu, Apr 2, 2009 at 1:17 PM, Steve Swinsburg
<s.swinsb...@lancaster.ac.uk> wrote:

All,
I have some questions regarding deserialization. On a page in my

any of my transient fields are called. A simple example:
private transient Logger log = Logger.getLogger(BasePage.class);
Later in my code I use my log object in the onSubmit of a button:
log.debug("MySearch() search.getSearchInterest(): " + searchText);

occurs.

then correct?

or bad practice?
It is working correctly I am just after any tips or caveats.
ie this works:
private void readObject(ObjectInputStream in) throws IOException,
ClassNotFoundException {
// our "pseudo-constructor"
in.defaultReadObject();
// now we are a "live" object again, so let's rebuild
log = Logger.getLogger(BasePage.class);

}

thanks a lot,
Steve

p.s.
Of interest, when I click 'back' in Safari 4, the whole page is

is called. Not sure what the go is with that.
ref: http://java.sun.com/developer/technicalArticles/Programming/serialization/

application, I click a link which takes me to a different page, then click 'back', and try to do something on the original page, but get NPE's whenever Which works fine in the normal workings of the page. If I click away from the page then use the 'back' button to come back to this page, then click the button that will call this same log.debug statement, thats when the NPE So, am I correct in my understanding that the page is serialized when I click away, de-serialized when I come back, and, since no transient objects are serialized along with it, that my 'log' will be null and this NPE is If so, this leads me to thinking that, in order for my page to set itself up again correctly, I need to override readObject() and re-setup all of my transient objects that would not be restored in this method? Is this a good reconstructed again (ie the constructor is called again) and readObject is not called, but in other browsers, the state is preserved and readObject()

--
Become a Wicket expert, learn from the best: http://wicketinaction.com
Apache Wicket 1.3.5 is released
Get it now: http://www.apache.org/dyn/closer.cgi/wicket/1.3.

---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@wicket.apache.org
For additional commands, e-mail: users-h...@wicket.apache.org

smime.p7s
Description: S/MIME cryptographic signature