Last month, Ibrahim Levent published a
detailed posting about the capabilities of a better web
framework on his blog.
I'd thought I'd describe my reaction to it, as well as how Tapestry
today, and Tapestry in the future, fits in with this vision.
Certainly there's a lot here, and there's a troubling lack of focus:
Mr. Levent is demanding very specific features that span a number of
domains. In effect, he's asking for an application server vendor to
deliver the One True Stack ... to which I say "good luck with that!"
1- Includes all core application layers (MVC):
Web framework should include data access, business logic, controller and presentation layers internally. As frameworks turn out to be an integration hub, it looses value. Every integration among the core layers introduces new complexity, new glue code, new dependency, and conflicting of intersecting features. If data access layer (Model) uses another framework, presentation layer (View) uses another framework, integrating these frameworks adds a very big challenge even if frameworks support each other. Replacing any framework causes many new problems later. For example, JPA is developed for data access independence but at this time you are limited only the features of JPA. IDE is a major development tool, but at this time we need an “Integrated Development Frameworks” environment within IDE. (Similar with ERPs that brought together enterprise applications under the same umbrella)
Choice is a good thing. I can get up and running quickly using
Hibernate; others prefer Cayenne or pure JDBC. I wouldn't want to
mandate just one, but Mr. Levent is correct that frameworks must adopt
the role of an integration hub, and Tapestry (with it's very dynamic,
very late binding Inversion of Control container) really fits that
I also chafe at the mention of the IDE: we've been down that path
before (.Net, JSF) ... what we really need are tools that work with a
minimal amount of support from the IDE.
2- Avoids heavy-componentization:
I come down strongly PRO componentization; that's been the focus of
Tapestry since day one. Mr. Levent is correct that as more of a page's
content is encapsulated inside components, the high level templates
(page templates, in Tapestry terms) start to loose their ability to be
view stand-alone, outside of the running application. However, I'd
rather trade productivity and consistency (and testability) across my
application for this one "feature". Here's a better question: how hard
would it be to set up your application to run for the designer?
Tapestry can allow a designer to run the application and see changes
in real time.
3- No new tag markup or page template:
Tapestry really excels here, as the Tapestry Markup Language templates
are just XHTML with a namespace for the Tapestry parts; and those can
be limited to just a
t:id attribute with all other
details in Java code. I don't do it that way ... it's more work for
little gain, but a purist can appreciate this.
Even at the opposite extreme, a "heavily" instrumented Tapestry
template is still pretty light, with no true Java code (though a few
proeprty names and expressions will show up).
4- No XML usage:
Heavy XML usage for configurations makes programs hard to develop, hard to understand, hard to test. One example is “Page Flow” information in XML files. Another example is bean configuration. Yes, pulling this information makes it flexible but who needs it? How many times your page flow changed? How many times did we utilize flexible bean configuration? What about source code readability? I don’t like “Dependency” so “Dependency Injection”. I think dependency is not free that you have to manage its subtleties. Here is my anti-pattern “Dependency Rejection”. XML can be used in other useful places like AJAX messages or data import-export.
Here's where I agree; only Tapestry templates use XML. Tapestry 5 did
away with all other XML (except for the ubiquitous web.xml, which is
only touched once, when first creating a Tapestry project).
I feel that Mr. Levent is really missing the boat here; properly used Dependency Injection is incredibly important. Dependency Injection is what makes a clunky dinosaur of a language like Java useful, scalable in complexity, testable, and extensible (via late binding). To paraphrase: Dependency Injection is like violence; if it isn't working for you, you aren't using enough of it!
Dependency injection is critical to source code readability because it allows you to easily break your code into small, focused bits that each perform a well-defined function. The IoC container's job is to put all those tiny, testable bits back together into a running application. Tapestry IoC and Guice do this with aplomb.
5- Has its own web GUI page elements:
Rich web elements (say light components) are generally found only in JS or AJAX libraries. Web frameworks should provide rich elements like; Calendar, Dialog, Menu, Popup, Progress Bar, List, Grid, Tab (With sub-levels), Master-Detail Windows, Child Windows, Record Navigator etc. Developers can easily extend these elements. We are still turning around simple features like table sorting, filtering etc. We should step ahead. There is still no desktop-like web grid components to use (I see only in JS libraries) that I mentioned in my previous blog post.
Tapestry does well here (and this requirement seems to contradict
item #2). In any case, Tapestry has decent support built in, with lots
of great 3rd party support.
Fundamentally, Tapestry is page oriented: the Ajax effects can be well
integrated, but not the degree of either a Google Web Toolkit
solution, or something entirely hand-tooled (on top of Direct Web
6- Code generation:
Code Generation makes “Rapid Development” possible. Every part of software should be generated (Generative Programming); CRUD data access classes, business code, controller code, and view pages. Code generation takes development one step ahead of “Drag and Drop” WYSIWYG editors. If web framework facilitates code generation, developers could jump to customization details of application instead of building everything from scratch (MDA).
I disagree here: I don't like code generation unless it happens at
runtime. If you look at Tapestry's "scaffolding components"
(BeanEditForm and Grid particularly), you can see this ethic: the
application is dynamically assembled at runtime. Likewise, all of
Tapestry's meta-programming happens by class instrumentation at
runtime, without a tedious build stage.
Again we return to integration; Tapestry has a set of libraries built
on top of Prototype and Scriptaculous. Many applications also bring in
jQuery. They all mix together nicely on the client side.
8- AJAX support (Asynchronous Communication):
AJAX eliminates bothering page-refreshes. Web frameworks should properly blend AJAX functionality into their code architecture. AJAX requires server-side coding. As we make client runtime powerful with AJAX, GUI state management code is duplicated. For example, if we update and fill a combo-box with AJAX call then server-side bean that is bound to this element is not aware of this state change. We have to change server-side state as well. AJAX functionality should be implemented without code duplication (Another interesting trend is AJAX MVC).
... and the nature of component encapsulation is to allow Ajax without
the fuss and duplication alluded to here.
9- Portable among application or database servers:
Application and database portability is not easy. In Application Server side, class loader policies change, session management changes, deployment model changes etc. In DBMS side, join clauses change, paging, and sequence generating changes. Web frameworks should provide portable packages for different platforms. On the other hand, some web frameworks have their IDE and Application Server (believe me even DBMS). I think we must leave this job to the famous bright products (IDEs and Application Servers in the market).
This can be a sore point; the servlet API doesn't specify a few
important behaviors for Tapestry (that mostly show up only in a
cluster). I'm not sure what a "bright product" is though? Any clues?
Tapestry does work on popular servers (Jetty, Tomcat, WebLogic)
because it's careful to follow the Servlet API rules, especially with
respect to careful use of the HttpSession.
10- Input validation:
Data input validation is a very important feature. If validation doesn’t occur in application, database error occurs. Database errors are not user-friendly. Some validation errors may not be related to database. Programmers need automatic validation according to database object metadata. Custom validations should be added if needed.
I agree, and add further, that validation should occur on the client
and then be re-executed on the server. Once you escape from the web
tier, the errors get uglier.
Because of bugs in frameworks, all average developers become framework expert spending valuable time to figure out the problem. “Focusing business problems” is lost. I read many open source framework hacks and workarounds in many blogs which is not the task of developer.
As if proprietary code is bug free? This one gets my blood pressure
up ... I can't tell you how much time I've spent stepping though
WebLogic code, guessing at what's gone wrong (where a bit of source
code would have helped). The alternative to Open Source is to still
become a framework export, but pay through the nose for the privilege,
and deliberately let yourself become helpless, in thrall to your vendor.
12- Handles exceptions user-friendly:
If error or exception occurs, user-friendly messages should be returned. Application programmer has some responsibility for this but web frameworks may ease this task.
Tapestry excels here; I strongly maintain that Tapestry's exception
reporting is the best of breed, with a detailed exception report and
lots of contextual data ... and the ability to easily turn it all off
or otherwise customize what happens when things go wrong.
13- Eliminates double-click, double-submission problems:
Double-click may cause double-submission. Double-submission may cause unexpected errors in application (2 threads tries to do same thing). Web frameworks can eliminate this problem even in client-side without going to server.
form or submit button goes a long way here! But a better solution
intercepts the duplicate submission and that requires some
coordination across the server cluster, which is why it isn't in
14- Authentication and authorization support:
User login (authentication) is still developed by programmers without knowledge of SQL-Injection attacks. Web application authorization is still missing. Who will be granted for CRUD on which application etc.?(User roles, permissions) I am sure that in every enterprise web application, application authentication and authorization is re-invented.
Is it the role of the application framework to define your security
constraints? In a very constrained world, such as content management
system, these roles and their application is well defined. I the real
world of real applications, it's much harder to pin down. I've worked
on many apps that had somewhat intricate permission schemes, and the
ability for some users to "jump out" of those schemes.
That being said, Tapestry's modularity means that a standard security
can just be "dropped in". That's what we've been doing at Formos; we
use a standard permissioning system, based on page and method level annotations.
15- Security controls for web attacks:
Web frameworks should prevent web security attacks like; Cross-Site Scripting (XSS), SQL Injection, URL Manipulation, HTTP Injection, Session Hijacking etc. Web client data is un-trusted and open to tampering so this is why we can’t quit totally server-side validation for the sake of client-side validation.
Tapestry does a great job on these issue; XSS is virtually impossible,
as all output generated by Tapestry is "filtered" unless you
specifically ask Tapestry not to. SQL Injection can't occur in a
world where you are using Hibernate or another layer to generated
prepared statements (this isn't PHP!). URL Manipulation is also
somewhat of a non-starter because URLs are linked to components and
components are configured on the server side to perform specific
functions. It's not like Struts or Rails where you can hack a form
submission to turn your admin flag on!
As I mentioned earlier, Tapestry re-performs input validation on the
There is a concern in Tapestry in that Forms store serialized object
data on the client side. This is both insecure and inefficient. A
future release of Tapestry will address this by either encrypting or
signing the data, or by storing the data server-side and just sending
a "token" to the client.
16- Reporting integration and barcode support:
Reporting integration is important. We need reporting products/frameworks integration. Would you use your data access objects in your reports? Would your reporting engine use the same JVM runtime? Barcode is not a general requirement but in ERP applications it is very useful (AI/DC Automatic Identification/Data Capture). Barcode printing, barcode reading and matching may be provided by your web framework.(What about RFID?) Would your reporting product support your application barcode?
This is one of those entries in the original blog that simply makes me
wonder; Mr. Levent clearly works on a specific category of
applications, but I certainly have never written an application that
needs to know about barcodes. Barcode reading? What does that even mean in terms of a web framework?
17- Messaging and workflow integration:
Web frameworks may support easy integration with messaging (JMS) and workflow products. Workflow is one of major element of BPM (Business Process Management). In some middleware stacks, this is included (i.e. JBoss Seam jBPM). Web application frameworks may support business events and workflow activities. These events can also be used to feed messaging backbone (ESB).
Even the example here is odd, and reinforces my earlier points: JBoss
Seam doesn't have built-in workflow, its the Seam jBPM module that
integrates into Seam. So as long as you are good at
integration, we're in the success zone. And Tapestry is great at integration.
18- Application to application integration (i.e. Web Services):
In Java, there is external system (EIS, legacy) integration API, which is JCA, but inter-application communication within same JVM is not standardized. Let’s say we have 2 applications and one should use some call other application code. There is no standard for this. Basic solution is just adding other application’s path into its class-path and then using other application objects. We developed an Adapter API for standardization of this. In one-application environment, this is not a problem but if many applications are required to communicate, it gets more important. You can even convert your APIs into web services when necessary (integration with remote or non-Java systems). Web frameworks may provide tools for web services code generation, deployment and monitoring.
Mr. Levent has moved, about here, from some strong goals and
guidelines for a web application framework to a kind of development
19- Admin application for run-time process and user session
This is very important in point of user and system management view. What are my users executing at the moment? Which applications take longer to finish? Which users are on-site? Which pages are they surfing? In each session, which objects are they created? What are the URLs that a user requested? Which SQL statement did a user execute?
This is an interesting concept and one that could perhaps be
implemented using Tapestry's various meta-programming facilities. I've
definitely been thinking long-term about a Dashboard facility.
20- System resource management:
If your application runs big queries that require a lot of system resource (CPU, RAM, DISK I/O), we are faced the reality that resources are limited. If applications don’t restrict user processes, then system will consume its all resources and will not respond to even small processes. For the sake of system availability some user may be rejected by system. Web framework may have such limitation API’s.
This concept is a tricky thing to bootstrap; if your machine is truly
strapped, it may have trouble just getting to the point where it can
determine how strapped for resources it really is! I know of no
general purpose web
frameworks that have this kind of feature.
21- Cluster support:
When server load is high and performance is a major concern, load-balancing is required. Application server clustering will not suffice, web frameworks must support cluster architecture. One simple example is framework’s id generators. They will collide in clustered Application Server environment.
I'm not sure what framework id's he's getting at here. Clustering a
servlet application is generally quite sufficient, and clustering
Tapestry is even easier, as it is very careful about what data is
stored into the session. Tapestry is also good at keeping mutable
objects stored in the session "fresh" when they are updated, but
mostly it stores many small immutable objects where other frameworks
store large mutable objects.
In terms of IDs; session ids can have, for example, DCE ids that can
be cheaply generated anywhere with a guarantee of uniqueness (they
just tend to be quite large). Database ids are generated, efficiently,
by the shared database.
22- Multi-database, multi-company, multi-window, multi-session
Application user may need to work on multiple database instances. One user may have to work with multiple companies. User may want to use multiple GUI windows. Web framework should handle or prevent state corruption among windows. User may need to work on the system with many sessions.
To me, this indicates a single application deployed, and perhaps
"skinned", multiple times ... or represents a single application that
is capable of connecting to multiple databases at the same time.
Multiple windows can be something of a challenge; a single server-side
session is shared across windows. Tapestry can encode state into URLs,
which is handy but ultimately limiting. I think in the future Tapestry
has the best chance of dealing with this cleanly because there's the
gulf between persistent page fields and the session, which allows
Tapestry to arbitrate ... literally, store different values in the
session for different windows, but the same user. Not something
implemented today, but quite possible.
If there are global users, then i18n support is important. One key aspect here is Application Server and DBMS should also support your localization.
Tapestry has greate L10N support; applications can have localized
message catalogs as can individual pages and components. Templates and
assets (images, stylesheets, etc.) can be localized as well. Tapestry
uses your browser's reported locale, but this can be overridden
programatically. In Tapestry 5.0, you'll receive a cookie with your
"true" locale. In 5.1, the "true" locale will appear in the URL (which
is more search engine compatible).
24- SSL support:
If web application is wanted to be secure in insecure networks, SSL-support is important. SSL deployment in HTTP Server would not be enough. Even if SSL is not used, frameworks must encrypt sensitive data between client and server, like user passwords.
You may mark Tapestry pages as secure, using an annotation. Tapestry
will automatically use HTTPS when building links to secure pages, and
will reject any attempt to access a secure page using insecure HTTP.
25- Document attachment:
In every enterprise application, document attachment is important. Users may want images, Excel documents attached to their application records. Every programmer first search for an upload utility then tries to understand server document folders. Instead, built-in functionality saves valuable time.
Back to a wish list and not a real framework goal.
26- Mobile device support (i.e. Internet Explorer Mobile):
If we want to plan mobile access to our applications, how can we do this with web technologies? Many mobile devices have built-in web browsers and we may run our applications in these browsers. Web framework mobile support would be very beneficial at such cases. Otherwise, you should explore mobile web browser limitations by yourself.
I have long maintained that an application for a mobile device and an
application for a desktop browser are not the same
application. Creating a useful version of an application for a size
and bandwidth limited client is more than just choosing new fonts and
omitting a few options ... to do it succesfully is a completely
different flow, and therefore, a different application (or at least, a
seperate corner of the application).
You often hear about a magic XST transformation (Coccoon, anybody?)
where a single service layer could be vended out in multiple formats.
But I've never seen one in practice that worked, scaled and was
maintainable, never mind acceptable to end users.
27- Portal features:
Partial web components should be supported to use in Portals or external sites. In portal terminology, its name is portlet. There are many synonyms; Widget, Mashup etc.
Tapestry 4.0 was a great platform for Portlet development, that will
return in Tapestry 5.2.
Application task may be batched and scheduled. After task completion, users may see results.
I have long thought of a layer for Tapestry to leverage Quartz for
this purpose. Again, Tapestry's current goal of being a comprehensive
user interface layer (rather than a total vertical
application framework, which is what Mr. Levent is looking for) has
made some of these non-goals for Tapestry.
29- Keyboard hot-keys:
Users, especially old TUI (Text UI) users want keyboard hot-keys. Buttons, command icons should be bound to hot-keys. Web frameworks elements can support this instead of developing in every application.
encapsulated by Tapestry.
30- Alerts between users:
Users may want to send messages to each other or system admin may want
to send messages to users like notifying a shutdown or an application
restart. This feature will be very handy.
Again, a wishlist item that could easily be implemented for a specific
Mr. Levent has brought up a number of interesting concepts, and a
number of real oddities, in his quest for the "improved web framework"
(in fact, he's looking for a vertical application framework with some
very specific niche capabilities).
I can't say that Tapestry fits his bill perfectly ... but I can say
that Tapestry would be my first choice to anchor the stack that
would meet his needs. The most important features of his
"better web framework" are already present in Tapestry today.