useBean type attribute??

[Joe San]

Hi Guys,

What happens when we just say

<jsp:useBean id="person" type="foo.Person" scope="page" />

In the HFSF, they say it works perfectly fine provided if the person attribute already exists in "page" scope. What it means???I'm not understanding. Can anyone help me what they really meant here??

Thanks in advance.

[Deepak Bala]

When you use the "class" attribute, the class specified there will be instaintiated using the public no arg constructor, if the attribute in request, page, or session, or application scope does not exist.

When you use the "type" attribute, you better make sure that the attribute is already available in the scope you specify. If its not available... KABOOM !

[Joe San]

Hi John,

So that means, with only the type defined in the useBean tag, we are telling the container that use the reference specified in the type wherein the object is already available as an attribute??? Am I confusing myself???

[Boobalan Pillai]

Yes you are right..with type attribute object should be already exist in any one of the scope...because type would be an interface or abstract ,you cannt create object for that if the corresponding class type does not exist...

regards
Bala.

[Celinio Fernandes]

If no existing bean matches the type, no new bean instance will be created and an InstantiationException is thrown.