Thiago, I think he's misunderstanding the point of Tapestry. You
never do scripting in the views. In fact, you never do scripting.
Scripting (in web templates) mixes display layout and display flow
with business logic, data flow, and user workflow. They're all mixed
up together. Anyone used to that will have a hard time seeing how to
accomplish the same features in their application without access to
any ability to embed scripted code into the view.
Amit, you need to re-think your orientation when using something like
Tapestry. All of your code is in controllers, with the exception of
some display layout flows like loops, conditionals, and such. There
are components for these, but unlike JSP tags, they do not "unwind"
into code, they are components and all the pages are composed, with a
rendering engine that asks components to render themselves or their
templates, and their child components, who are in turn asked to
render. It's a very different paradigm.
In practice though, if you're thinking of having a lot of logic you
would imagine going into scriptlets or the like, factor that code into
methods which return the displayable result. For instance (this code
is made up on the spot):
<%
CreditCard cc =
myDao.getCreditCardByNumber(request.getProperty("ccNumber"));
%>
<h2><%=cc.getType().getName()%> card</h2>
<p>Card <%=cc.getNumber()%> has the following purchases today:<p>
<table><tr><th>Date</th><th>Vendor</th><th>Amount</th><th>Posted?</
th></tr>
<%
List<CCTransaction> txns = myDao.getTransactionsForCC(cc.getNumber());
for (CCTransaction txn: txns) { %>
<tr>
<td><%=MyUtil.format(txn.getDate())%></td>
<td><%=txn.getVendor()%></td>
<td><%=MyUtil.formatCurrency(txn.getAmount(),"USD")%></td>
<td><%=txn.isPosted()%></td>
</tr>
<% } %>
The above is pretty ugly JSP code, and even with Struts or other web
MVC frameworks that use JSPs as a base, it can be that ugly. Tapestry
goes a different way. (this code was also cooked up at 8am after a red-
eye flight... it is uncompiled, let alone untested. Don't cut-and-
paste it. This example uses credit card, but doesn't authenticate and
is massively insecure. It's only paying attention to a certain aspect
of things.)
MyPage.java
...
public class MyPage {
@Inject
private MyDao myDao;
@Property
private CCTransaction currentTransaction;
@Parameter(required=true)
private String ccNumber;
@Property
private CreditCard creditCard;
@SetupRender
public void init() {
//do validation stuff...
creditCard = myDao.getCreditCardByNumber(ccNumber);
}
public List<CCTransaction> getTransactions() {
}
}
MyPage.tml
<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_0_0.xsd";>
.....
<h2>${creditCard.type} card</h2>
<p>Card ${creditCard.number} has the following purchases today:<p>
<table>
<tr><th>Date</th><th>Vendor</th><th>Amount</th><th>Posted?</th></tr>
<tr t:id="layout" source="transactions" value="currentTransaction">
<td><t:output t:format="YY:MM:DD HH:mm"
t:value="currentTransaction.date"/></td>
<td>${currentTransaction.getVendor}</td>
<td>USD ${currentTransaction.amount}></td>
<td>${currentTransaction.isPosted}</td>
</tr>
</table>
The display logic and flow control is in the template, but no actual
data lookups or business calculations. I don't know if it helps, but
hopefully it gives you a taste of how things are different.
On this note, it might be good to have some side-by-side mini-examples
which show how someone would do something in vanilla JSP, in Struts,
in JSF, and in Tapestry so people can make the mental leap. Annoying
to build, I know, but potentially highly useful.
regards,
Christian.
On 20-Mar-09, at 08:07 , Thiago H. de Paula Figueiredo wrote:
On Fri, Mar 20, 2009 at 1:53 AM, Amit Nithian <anith...@gmail.com>
wrote:
1) With Tapestry, I understand the Controller is effectively the
Page and
Components with the View being the template files. I haven't seen any
examples of complex "scripting" in the templates where you can
build complex
views.
Please give us an example. Your description is a vague enough for me
to not understand what you're talking about.
How do people build nice looking, complex front ends with Tapestry
backends?
Again, I don't know exactly what you're talking about. Anything you
can do with HTML, CSS and JavaScript you can do with Tapestry.
Tapestry deals with the server side of things, but also helps with
some JavaScript issues, specially AJAX.
--
Thiago
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