Heiko Gottschling wrote:
>
> Hi,
>
> I'm wondering what's the use of beans with JSP. In my (humble) opinion,
> beans are useless... everything I can do with beans can be done with
> "normal" java objects as well.
In general, it's much easier to maintain a web application if you keep
the code in the JSP pages to a minimum (see the archives for tons of
discussions about this). Using beans, and custom actions, is a good way
to achieve this goal.
> For example,
>
> <jsp:useBean id="myBean" class="MyBean" scope="session">
>
> can easily be replaced by
>
> <% MyBean myBean = new MyBean();
> session.put("myBean", myBean); %>
No, <jsp:useBean> only creates an instance if the bean can't be
found in the specified scope.
> Moreover, beans obviously have some disadvantages:
>
> - the syntax is very awkward. Instead of writing <jsp:setProperty
> name="myBean" property="prop" value="val"> I can write
> myBean.setProp("val"), which seems much smoother
> - Construction of beans seems to be limitied to using the
> (argument-less) standard constructor. Constructors with arguments are
> not supported.
> - Using <jsp:setProperty>, only String properties can be set. If I want
> to set any other properties, I have to access the bean directly anyway.
No, <jsp:setProperty> can be used to set properties of any type (see the
JSP specification for details).
> So, I'd really like to know what's the big deal about beans? I would
> rather write my JSP pages without using beans, but I'm wondering if I'm
> missing something? What's the reason that beans were introduced to JSP
> in the first place? Are there any situations in which the use of beans
> provides a real advantage over the "traditional" approach?
The main reason to use beans is to minimize the amount of code in the
JSP pages, see above. I look at beans primarily as carrier of information,
for instance all information about a customer. The bean can be created
by a servlet, e.g. getting the info from a database, and then passed to
a JSP page where the properties are displayed using <jsp:getProperty>.
--
Hans Bergsten [EMAIL PROTECTED]
Gefion Software http://www.gefionsoftware.com
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