Nah, you wouldn't need that. You can do things like:
.tml:
<div class="${transactionClass}">...</div>
.java:
public String getTransactionClass() {
switch(transactionType) {
case ACCEPTED: return "validtransaction";
case DECLINED: return "declinedtransaction";
default: return "";
}
And so forth.
You can also do things like choose specific pieces to render via
"t:block" and the "delegate" component:
<t:delegate to="transactionBlock"/>
<t:block id="acceptedTransactionBlock">
... stuff in here
</t:block>
<t:block id="declinedTransactionBlock">
... other stuff in here
</t:block>
.java:
@Inject
private ComponentResources resources;
public Block getTransactionBlock() {
switch(transactionType) {
case ACCEPTED: return
resources.getBlock("acceptedTransactionBlock");
default: return resources.getBlock("declinedTransactionBlock");
}
}
All of this is to say that there are many ways to make your displayed
content highly dynamic, all while keeping the structure of the page
static.
Robert
On Mar 21, 2009, at 3/212:06 AM , Amit Nithian wrote:
Thanks both for your answers! They were helpful. I guess my angle
was more
from an older ASP web application paradigm or even old style PHP which
didn't have much distinction with models, views, and controllers. My
only
question/complaint about the jumping back and forth between the
template and
Page class is what do you do when you want to do different things
based on
something like an enum instead of simply a boolean? Would you have
to have
multiple boolean functions one for each possible enum value that you
wish to
test?
For example, if I have (using a credit card theme here) an enum for a
transaction status with values of DECLINED and ACCEPTED, if I want to
display ACCEPTED in green and DECLINED in red, would I have to have
two
functions isDeclined and isAccepted and do an t:if to control red
and green
display? Sometimes here, I feel, is where having scripting
capability helps
in the display of the page to prevent a page class with a ton of
simple
getter methods.
Also can you explain what this does?
@Parameter(required=true)
private String ccNumber
Thanks again and I'm excited to continue using Tapestry!
- Amit
On Fri, Mar 20, 2009 at 6:10 AM, Christian Edward Gruber <
christianedwardgru...@gmail.com> wrote:
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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