Re: JSP newbie - can I use JSP to access exiting java classes without
re-write to javabeans
I have access to existing Java classes for users/hardware written
by members of my team, and want to write some web-pages to query and
display this data using JSP . Do I need to re-write the Java classes
as java beans and utilise the "usebean"
Please be careful with your spelling on tag names and such.
call to import this into my JSP (not a solution I'd like) or is there another way I can get access
to current Java classes that are not Javabeans...????
<jsp:useBean id="commander" class="abc.xyz.Commander"
you always can use
abc.xyz.Commander commander= new abc.xyz.Commander();
If you like, of course ;)
Which, hopefully, you won't, as it's terrible style. Ideally there won't be
any scriptlet at all in your JSP.
The good news is that there are at least two ways to tie in to your existing
code. Bear in mind that tying in to existing code is one of the main things
we do in Java.
One way is to follow the "Model 2" version of the Model-View-Controller
pattern for your Web app. The JSP will use JSTL and Expression Language (EL);
not a <jsp:useBean> tag in sight. That will be the View. The Model will be a
thin wrapper of (bean) classes that manage the interaction with the existing
library of interest. The wrapper will assemble an object that contains
various information that you are going to display, absent any display or
formatting meta-information. The Controller is a servlet that is the target
of the form submission from a JSP. This servlet will unpack the request and
pass relevant data to the wrapper. It will insert the result object into the
request attributes, then forward() through a RequestDispatcher to an
appropriate "next" JSP - the next View screen.
Another way is to create custom tags that directly invoke the wrapper classes
and present result data in the rendering of the tag.