Arved Sandstrom wrote:
It's not just JSF 2.0; it's also JSF 1.x. Bearing in mind that the backing
bean instance is ultimately where values are stored, it makes sense that
in the RENDER_RESPONSE phase the getters are called to obtain the values
to display. The reason you'll see a second call to getters is that during
PROCESS_VALIDATIONS it's necessary to obtain values on the bean in order
to support value change listeners. This happens in a postback (form
submit) only. Sometimes you'll see even more calls if you have complex
page logic involving values, like to compute a "rendered" attribute.
So this double call during postback is something to anticipate. Don't put
code in your getters that will execute twice if you don't want it to
execute twice. If the code does need to be there - like fetching data from
a DB - then you put in appropriate guards to make sure it executes once
only. This isn't caching - it's understanding the JSF lifecycle and
understanding that getters can execute twice during certain HTTP requests.
As the Seam article mentioned, if you've got value expressions in an
h:column inside h:dataTable, then you can also get considerably more
getter calls. Depending on what your getters are doing (what exactly are
the values in your table, what kind of persistence do you have, etc) then
not only are you loading up a backing list twice but you may also be
calling the DB to populate other columns for each row in that list.
If you can provide an example of an offending page and the corresponding
backing bean it would be helpful.
ok, thank you for your answer.
there I still found another page with that problem:
http://seamframework.org/Community/HowtoAvoidMethodOrGetterToBeCalledSeveralTimesByCachingResult
well, the getter-Method will give back an object.
that object will be the same during one rendering of the page.
If not, the rendering would get problems, I think.
So why to create that object again and again during one rendering?
I have only one of that getter-method in my xhtml-page.
If there would be more, ok.
And why to call the getter-method during leaving the page?
I ask, if it make sense to call it one time,
but in my case it does it 14 times.
The code is becoming very, very slow that way.
I only can understand, that there is a huge bug in jsf.
That is so totally not the case. It's like you didn't read Arved's answer, or