How Sun could fix Swing and promote innovation and unification in the UI space

I saw Jonathan's post on Swing 2.0 and it was late, I'd had a nice glass of wine so I fired off a wacky idea on twitter which got some interesting feedback. I'd like to just expand on the background of the idea some more as I'm not so sure it is so wacky an idea afterall. Its feeling more and more like a no brainer and complete win win.

I'm afraid this post is gonna be quite long. (Holy crap - no blogging for ages and then two big posts in a week!) - first some background...

Programming Rich Java Applications Is Sucky
Imagine the scene. You're part of a team of Java developers; you're tasked to write a rich application. It might be a commerical app or some intranet enterprisey thing, or some rich application to improve the user experience of some web app (like the iphone versions of facebook/twitter/gmail etc) - whatever. So what do you do?

You've a mindnumbingly broad choice to choose from - here's just a few options...

• Swing
• SWT/JFace/EclipseRCP
• web app with some combination of Ajax/JavaScript/GWT libraries
  
• JavaFX?
• Flex/Flash

Each have their own strengths and weakesss. Though they all totally different. Write for one of those then later on you're requirements change (making one of the other options more attractive) and you've gotta scrap it all and start over.

Write once and run everywhere - except if your application has any kind of user interface.

This is maybe why so many Java folks like writing server side apps; as the client side in the Java ecosystem is such a mess.

Helping Swing Developers
Lets imagine you pick Swing to develop rich applications. In its day, Swing was a good piece of work by Sun. However that day was in the nineties :)

I've done a fair bit of Swing in my time and worked on Swing projects; in my experience you can spend years trying to tart up a swing app and it still looks - well like Swing. You can get a day of a good web designers time and make any web application look stunning via HTML/CSS/images. It just seems so much easier to hack up HTML/CSS to look great. Just compare some great web 2.0 applications out there to your typical Swing UI. As an end user which would you rather use?

As a developer one of the big PITAs with Swing is layouts, styling and working with images and links. The standard layout managers suck. (GridBagLayout anyone?). Yes I know there's a zillion layout manager implementations out there - all doing different things well with different results & rendering bugs - and which one do you choose?

Generalizing hugely but most of the work that goes into most data entry-ish rich applications is creating loads of screens which are full of text, images, links and some rich widgets with plenty of documentation, popup help, cheat sheets and then laying it all out and styling it nicely. Swing is lousy at these UI basics. Sure its got a good JTable and JTree, something that many a web developer will probably have been envious of at some point or other when hitting gremlins in their JavaScript table/tree - but at laying out forms, dialogs, help screens, documentation and working with links and images - well its kinda sucky.

Swing developers should be using HTML/CSS for this - its great at it. The web browser is the best layout manager we have - and HTML/CSS is the best standard for laying out widgets. With HTML/CSS there's a ton of tooling out there too for viewing/editing/styling. You can then pass the HTML/CSS to your web designer while the Java Swing hacker focusses on the business logic or the complex widgets.

Plus any time you spend hacking HTML/CSS - being a simple, standard text format used inside web browsers means you can reuse your work in web applications as well as rich applications. You don't spend your time hacking up some Swing Java code thats only useful inside a Swing application.

My Proposal
So my proposal is, in Java 7 we integrate WebKit into the JVM. Why WebKit? Well its smaller and easier to integrate than Gecko; Apple chose it for Safari & iTunes and the iPhone and Google chose it for Chrome and Android. If its good enough for a cell phone surely we can fit it into a JDK/JRE for a rich desktop application?

If Sun wanted to get clever, the browser engine could be pluggable; letting folks pick different versions of WebKit or FireFox/Opera/IE - but lets not go there right now - lets just assume a recent WebKit version is baked into the JRE/JDK.

Some would argue it should be optional; but then given the size of the JDK/JRE there's a ton of not-that-useful stuff in there; I'd rather include it by default over loads of whats there :) But then the JDK/JRE is getting more modular right - so lets leave the optional nature of WebKit for when the JDK/JRE is truly modular - right now its huge; so if a cell phone can include it, so can a JDK/JRE :)

Next we have a standard Java API for creating a BrowserPanel which can be hosted inside any AWT/Swing/SWT/JFace based UI. So a browser window becomes a standard embeddable widget in Swing and SWT/JFace/Eclipse. There should also be an API for controlling the browser (loading/saving URLs and interacting with the DOM).

Finally I'd like any AWT/Swing/SWT/JFace/JavaFX component to be usable within the DOM of WebKit. So I could create a nice HTML page with nicely formatted and CSS'd text, images, tables but then include, say, a JTable and JTree in the middle somewhere; letting the browser do the layout stuff.

This last requirement might seem complex but thats exactly what Flash and JavaFX are already; plugins which create custom UI widgets within the DOM.

For those that are aware of GWT Hosted Mode; this proposal is very similar - embedding a web brower inside the JVM as a single process. The main differences are

• we need a standard API to spin up browser windows and embed them inside any Panel and to be able to bind any UI Panel inside the DOM easily (e.g. finding a div by ID and binding it to a JTable)
  
• we don't need the restriction of being able to turn the Java bytecode into JavaScript - as for standalone Swing/rich apps you can can leave it as it is :). So any Java code could work with the browser. So none of the GWT restrictions would apply - plus you could use Groovy/Ruby/Python/JavaScript/whatever
  

Benefits for Swing Developers
Swing would instantly get an awesome, standards based layout engine capable of easily rendering styled text, images and widgets while dealing with other kinds of media. Through the use of CSS Swing applications would be easily styled using all the existing HTML/CSS tooling.

Swing developers would then have the best of both worlds; their Swing widgets still working when they want to use them - but having the great power of the browser window around the widgets to make the layout easy, powerful and great looking.

Since the JVM would now have a standards based browser; and it can already run JavaScript (and pretty much all other languages) easily - any Swing application could make use of any of the current GWT or JavaScript frameworks out there. There's a ton of innovation happening in the JavaScript/GWT space right now leading to ever better UI capabilities. e.g. take a look at SmartGWT and jQuery to name but 2.

Benefits for Web Developers
So how will this move - aimed at helping Swing developers help Web developers? The common PITA for web folks is often the browser imposes restrictions (for good reason) such as

• only being able to interact nicely with the single domain that serves the web page
• not able to interact with the file system
  
• only having 2 threads for communication
• limited connectivity (kinda hard to use native sockets, Java web stacks, JMS, native JDBC etc)
• unable to use things like Java2D/3D without via plugins
  

Plus there's dealing with the large number of different browsers of different capabilities & configurations & versions to support.

Now if you're making a public application; you're probably gonna have to deal with this (though now we're seeing custom apps for the iphone and android - maybe rich applications for public web sites are gonna be more common?). However loads of folks build web applications when they are really building internal, intranet applications.

So why not turn that web application into a desktop application making it run in a JVM? You can then package up your application with the exact, known browser you use and test with - and have access to all the features of the Java platform in your UI; whether its Java2D/3D, Swing/JFace, JavaFX or JMS/JDBC/JAX-WS etc

How this application is then made available to your users could come in different flavours; an application they install, Java Web Start (which might become cool again) or maybe even via JavaFX inside a browser?

So this could give a big safety net to folks building web applications. If you hit a browser limitation such as (say) a Canvas limitation? Just provide a Java2D version and ship a desktop application or Java WebStart it? It could end up that the JVM turns out to be the best place to host a web application reusing HotSpot?

Benefits for UI Developers
This single act of unifying the browser with Swing (and SWT/JFace) would provide a massive unification of standards based technologies for most UI development. More of the time spent building UIs would lead to creating more reusable standard artefacts (e.g. HTML and CSS) which are reusable in other contexts (e.g. transform HTML into PDFs or reuse the embedded microformats etc).

In these days of Dependency Injection; we're used to having a single code base then switching component implementations in different circumstances and environments; so we can start building more UIs which can be both web application and rich UI with each UI making the best use of its platform (zero install for web app, no limitations for desktop app).

Previously changing an application from a web application to a desktop application or vice versa was a massive undertaking (near total rewrite). Now it'll be pretty trivial to switch from one to the other as your requirements change. Applications will no longer be locked into one UI technology unable to move. UI code will become more aligned with the Write Once Run Anywhere mantra.

If folks create rich applications and web applications - there could be massive code reuse. While a web application and a Swing/JFace application are clearly going to have differences; they may use different views, components and features - there could be a huge amout of reuse of code. Even if the code reuse is only 30-50% its is big a saving; and we all need to do more with less these days. Though I can see - as UI frameworks improve, more and more chance of better code reuse across both.

Benefits for Sun
Folks have often said things in the past about Sun like

• Sun doesn't get the desktop, its not its core business
• Sun can't compete with Microsoft in its back yard (the desktop)

Sun is tightening its belt as is prudent for any company to do in the current climate. Sun has already de-funded SwingX. Also so far all the feedback and responses I hear from non Sun folks about JavaFX is at best lukewarm.

This move however would be a massive, positive move in the UI space and earn Sun a lot of kudos IMHO. Sun could then leverage all the innovation thats taking place in the browsers and WebKit in particular (HTML5, SVG, microformats et al) along with in the JavaScript worlds.

It would also mean there's not that much for Sun to do (other that integrate WebKit and provide APIs to control the browser and expose the DOM). All the innovation can then happen above this layer by the Swing, JFace & web developers and the WebKit & JavaScript communities. Immediately the Java ecosystem could then reuse all of the amazing work being done by the webby folks in JavaScript or by the GWT ecosystem.

i.e. the Java platform would then become a cool place to develop applications for (removing all the limiations with web browsers) with loads of buzz -and Sun doesn't really have to do much other than take all the credit :)

Heck they could even brand the WebKit-in-JVM as part of the JavaFX brand; so JavaFX doesn't have to beat Flash/Flex & Silverlight in the market to avoid looking like a turkey. JavaFX Platform (or whatever we call it - basically Java7 + WebKit) could turn into an instant success (anyone doing Swing or JFace would probably start using the embedded browser for better layouts & rendering) and if that helped the JavaFX Plugin (the JavaFX-as-browser-plugin) make some inroads to Flash/Silverlight its an added bonus. (Whereas right now JavaFX as just a browser plugin looks setup for failure to be honest, I don't see it ever eclipsing Flash).

Note its worth mentioning that there's similar moves to DOMs and whatnot being experimented with in the Eclipse ecosystem; who knows we could maybe finally unify on a single DOM?

Benefits for the Java Platform
Being able to build rich desktop and web applications in any language - without any browser limitations would be a massive boost to the Java platform; allowing folks to reuse all the good stuff from the OpenWeb and the Java platform (language diversity, IDEs and tooling, connectivity, Java2D/3D and even JavaFX).

We'd also hopefully see significant cross-pollination of the Swing / JFace folks and web folks to help UI innovation (which Sun doesn't have to try do itself).

If nothing else hopefully it will encourage more folks to write web applications and desktop applications to take advantage of both environments to provide better user interfaces for our users and customers for less effort.

Sounds like a win win for everyone doesn't it?

Update - JWebPane
So I should probably pay more attention to the JavaFX stuff :)

It seems that there is such a thing called JWebPane (see page 27 onwards of this presentation) which has been announced - so maybe this is gonna actually happen soon! :).

IMHO JWebPane sounds way more important to the Java ecosystem than JavaFX - I really hope it gets enough backing and funding from Sun to get completed and released real soon! Its not good to see nothing at all being released to the community despite it being announced about 7-8 months ago - so fingers crossed that whatever the legal/licensing issues are holding it back get resolved really soon.

We've just gotta lobby Sun to release it ASAP - then include it in Java 7... :-)

JAX-RS as the one Java web framework to rule them all?

One of the things about Java that sometimes gets made fun of is the huge number of Java based web frameworks. There certainly are many, of all shapes and sizes! I suppose there are quite a lot of different shapes and sizes of web applications out there but it sometimes seems like there's a 1-1 mapping between applications and frameworks :).

Picking the right web framework is probably a managers nightmare (Which one to pick? Pick the wrong one and we might end up using a duff dead framework that few developers know etc?). But it has lead to a ton of innovation in the web framework space. On balance I think competition and innovation are good things.

I'm a big Rails fan, I think its a stunning piece of work and one of the most impressive open source frameworks created in the last 10 years which together with Ruby, Erb and Rake is a good alternative to Servlets + JSP + JSTL + Spring + Hibernate + WebFrameworkOfYourChoice + SiteMesh/Tiles + Ant/Maven + a few other bits all in a surpringly small and easy to grok codebase.

JAX-RS came along initially as a way of writing RESTful services on the Java platform; using annotations and loose coupling to bind resource beans and their public methods to URIs, HTTP methods and MIME content type negotiation. I've said before I think its awesome, one of the most impressive JSRs we've had.

From the perspective of the controller layer I actually prefer JAX-RS to Rails routes.rb & controllers as

• the URI bindings are local to the resource beans which can be arbitrarily nested which makes refactoring much easier and avoids the complex routes.rb file with regex switches (I try and avoid regex whenever I can :)
  
• the loose coupling between the objects returned by the resource methods and the actual entity providers is clean; helping the application programmer focus on returning DTOs and letting the framework deal with the XML / JSON /Atom / multi-part-form marshalling & data binding stuff really helps. e.g. its easy to drop in support for new representations in a DRY way without changing the code of your resource beans (controllers), you can just modify an annotation
  
• static typing can be a handy thing when binding URIs and parameters to your controller. e.g. having String, integer, Date fields and parameters helps you having to explicitly convert things in your controller
  

There's lots of other stuff thats great in Rails though :-) but this post isn't a JAX-RS versus Rails post really - its focussing on the world of Java web frameworks for Java developers and the impact of JAX-RS.

So whats interesting is - if you want to build a web application with RESTful services (e.g. a human facing website with computer facing XML/JSON APIs) why would you use JAX-RS and another web framework? Why not just use JAX-RS as the web framework? So recently I've been musing, could JAX-RS be the one Java web framework to rule them all?

JAX-RS works well with dependency injection frameworks such as Spring, Guice, GuiceyFruit or JBossMC - you can basically pick whichever one you prefer. It also does all the heavily lifting of binding URIs and HTTP methods to resource beans and their methods along with supporting content type negotiation, headers and etags elegantly. For implementing great RESTful services in Java I've never seen anything close to touching it. The main question is what features are missing from JAX-RS being the main web framework?

Incidentally in this post I'm ignoring the server-side UI type frameworks like Wicket, Tapestry, JSF et al. I'm focussing on web frameworks that spend most of their time rendering HTML / XML / JSON and not building complex server side UI stuff and treating the browser as a kinda dumb terminal with the real UI work being done on the server side. Having had a horrid time using Tapestry and Hibernate together on some projects in the past, I'm kinda over the whole concept of server side UI web frameworks personally (I'm putting my flame-proof suite on now). I kinda think if you want to do complex rich web UIs, use wizards or complex flows, just use GWT or JavaScript on the client (or Flex/Flash for video or crazy highly graphical widgets) and keep the server side fairly simple and very RESTful. (But lets leave that discussion for another day... :)

In this post I'm only really considering frameworks like Struts, Stripes, SpringMVC etc. Thankfully WebWork and Struts merged together so at least there's been some consolidation in the space - and certainly Struts and Stripes are now kinda similar (and not too disimilar from SpringMVC). I wonder if JAX-RS will lead to further consolidation with web frameworks adding themselves as JAX-RS extensions?

So whats is missing from JAX-RS to be able to use just it for your entire web app and set of RESTful services and not have to use it with Struts/Stripes/SpringMVC and have to map some URIs into the web framework and some to JAX-RS?

Right now today there are definitely some holes; though currently I don't think there's that much missing. Here's my list of things I think are missing and how we could add them - I'm very interested in hearing if there's anything you'd particularly miss from Struts/Stripes/SpringMVC/whatever; please blog about it or post a comment and I'll do a follow up post!

Implict & Explicit Views
One great feature of Jersey is the support for Implicit and Explicit Views. Update: here's a link describing implict/explicit views. It basically allows the controller to delegate to the view layer (JSP/Velocity/Freemarker/GXP or whatever) using a default naming convention to find the template files in a directory named after the resource bean's class name and if required - the URI being requested. So a given Resource bean could have an index.jsp and edit.jsp templates for example - and referring to ${it.foo} inside the template would extract the foo property of the resource bean (you can override what 'it' is if you like but the resource bean is a very reasonable default).

Maybe the easiest way to understand implicit/explicit views is to look at the bookstore example in the Jersey distro; its basically the glue between JAX-RS resources and templates.

However there are some issues (which are being addressed particularly by the helpful folks on the Jersey list, particularly Marc and Paul) which basically revolve around having implicit/explicit views and (say) XML/JSON representations on the same resource bean using the same URIs and getting JAX-RS to pick the right one.

For example the URI "/customers" might return a HTML page for most web browsers but return XML/JSON if folks want to specify those MIME types in their Accept header. Right now Jersey tends to favour returning XML/JSON (long story but basically more specific URI paths are preferred over implicit views).

I'm pretty sure some kind of @ImplicitProduces annotation to allow implicit views to be associated to MIME types along with a higher priority/quality ranking specified in the next feature would solve pretty much all the issues with implicit/explicit views though am sure folks can think of other improvements...

Better Content Negotiation Support
It would be nice to see these issues resolved to be able to use RFC 2296 to be able to raise and lower the priorities (or quality) of the different representations.

e.g. you might want to prefer to return HTML over XML/JSON so unless folks ask specifically just for XML or JSON you return HTML.

Bizarrely Safari uses an Accept header of

text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5

which kinda means it prefers to render XML over HTML (despite rendering XML as plain text! Truly bizarre - what was Steve smoking that day :). Most web apps I know of would rather return HTML by default :)

So you might want to specify something like this on a resource to declare that you want to return HTML by default for most users...

@ImplicitProduces("text/html;q=1.0")
@Produces("text/xml;q=0.5, application/xml;q=0.5; application/json;q=0.5")
public class MyResource {
...
}

Those MIME Strings could be static final constants BTW to keep things DRY and not have to repeat a ton of MIME expressions throughout your resource beans and making it real easy to add a new MIME type to your code without changing your controller methods.

You could argue the out of the box rankings for HTML should be 1.0 and XML/JSON something lower, say 0.9 or 0.5 as thats what most folks would want.

Dealing with static content
The Servlet spec is a tad smelly in this area (and even in servlet 3.0) of not easily allowing you to mark URI patterns as being handled by the container (e.g. for static content or for JSP files etc) and mapping all of the rest to your default servlet. Hopefully as Paul suggests we can get around this using servlet filters in Jersey; but it'd be nicer if there was a better fix for this. (Rails wins here hands down with using regex to map URIs to controllers). But this is more a servlet issue than JAX-RS / web framework.

Multipart support
Having support for Struts style form beans; binding a multipart to a bean is very handy. MrStruts himself has contributed jersey-multipart which goes most of the way there. Allowing direct binding with any bean to avoid having to use the MultiPart class directly would certainly help.

Standard JAX-RS client API like Jersey's
While not that relevant directly to web applications; being able to implement a REST service by invoking other RESTful services - or being able to test easily any RESTful service using an API like Jersey's client - while reusing the cool entity providers on both client and server side - would rock.

GWT and JAX-RS client integration
If you're building JAX-RS services and want a rich web client then GWT is a great solution; you can reuse all your Java code on the client and server side and its very easy to debug the whole application in a single JVM in your Java IDE.

GWT ships with its own RPC mechanism and there are various REST libraries for GWT such as gwt-rest it'd be nice if there was an easy way to reuse the same DTOs used on the server side like you can with Jersey's client library from inside GWT. Using JAXB inside GWT is probably non-feasaible :) but it should be pretty easy to just use GWT serialization and then support it as an entity provider in the JAX-RS runtime. (Is there a MIME type for GWT serialisation I wonder :).

Basically as an application developer it should be trivial to be able to reuse RESTful resources in JAX-RS inside the GWT client reusing all those DTOs if you want to.

Update: some other suggestions
Julio Faerman mentioned on the Jersey list mentioned the need for better validation. So maybe we could integrate the validation layer from Struts/Stripes into JAX-RS? Or use the the Bean Validation API (JSR 303)?

Also Julio and Jon in the comments mentioned the need for managing conversational state so integrating Web Beans (JSR 299) as an option for bijection of conversational state on resource beans sounds a good possibility.

What else?
Those are the things I can think of so far. Can you think of any others? What are there features in your favourite Struts/Stripes/SpringMVC/whatever framework on the server that you really can't live without?

I'd love to hear others thoughts; do you think I'm smoking crack or do you agree? :)

Apache Camel goes top level!

Apache Camel is now a top level project at Apache - you can find it at http://camel.apache.org/. Yay! 

Many thanks to all the Camel Riders who made this happen!

JAX-RS as the basis of a DRY web framework

I'm with Sam that JAX-RS rocks and is a great basis for a RESTful framework for writing services. As I've said before, I think its the best JSR output since servlets and JPA. There's a great presentation by Stefan on it if you want to get up to speed fast.

I'd like to see something like the Jersey client standardised in JAX-RS - after all many restful resources are mashups of other resources and it makes testing of RESTful resources super simple. Also I love the implicit views in Jersey and hope they are kinda standardised some more; making the mapping between templates and resources more well defined across providers. But even in its current form, its great stuff.

Update: this is a good overview of JAX-RS I stumbled on the other day