All,I have some questions regarding deserialization. On a page in my 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 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);
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 occurs.
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 then correct?
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 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
reconstructed again (ie the constructor is called again) and
readObject is not called, but in other browsers, the state is
preserved and readObject() is called. Not sure what the go is with that.
ref: http://java.sun.com/developer/technicalArticles/Programming/serialization/
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