GWT 2.0: Cool Beans on In Browser Development Mode

Dietrich Kappe, Monday, October 12, 2009 @ 2:33 pm

I have a short list of things that I don't like about GWT. They are:

1. You have to use a special browser to debug in Java. That browser doesn't always behave the way IE or Firefox or Safari does. And you need OS specific distributions which can make it a little tricky to share a project between developers with different OS platforms.
2. GWT apps download as a massive hunk of code. There's no way to dynamically load code as you need it.
3. Building UI's dynamically, through a sort of XUL mechanism is a pain in the ass for non-standard components. Just talk to the Vaadin folks about the hoops they had to jump through.
4. The annoying dependency on SWT for tests.

So, what does 2.0 promise? To resolve these four things, and a few more. Check out the GWT 2.0 Milestone 1 release announcement:

In-Browser Development Mode: Prior to 2.0, GWT hosted mode provided a special-purpose "hosted browser" to debug your GWT code. In 2.0, the web page being debugged is viewed within a regular-old browser. Development mode is supported through the use of a native-code plugin for each browser. In other words, you can use development mode directly from Safari, Firefox, IE, and Chrome.

Code Splitting: Developer-guided code splitting allows you to chunk your GWT code into multiple fragments for faster startup. Imagine having to download a whole movie before being able to watch it. Well, that's what you have to do with most Ajax apps these days -- download the whole thing before using it. With code splitting, you can arrange
to load just the minimum script needed to get the application running and the user interacting, while the rest of the app is downloaded as needed.

Declarative User Interface: GWT's UiBinder now allows you to create user interfaces mostly declaratively. Previously, widgets had to be created and assembled programmatically, requiring lots of code. Now, you can use XML to declare your UI, making the code more readable, easier to maintain, and faster to develop. The Mail sample has been updated to use the new declarative UI.

Bundling of resources (ClientBundle): GWT has shipped with ImageBundles since GWT v1.4, giving developers automatic spriting of images. ClientBundle generalizes this technique, bringing the power of combining and optimizing resources into one download to things like text files, CSS, and XML. This means fewer network round trips, which in turn can decrease application latency -- especially on mobile applications.

Using HtmlUnit for running GWT tests: GWT 2.0 no longer uses SWT or the old mozilla code (on linux) to run GWT tests. Instead, it uses HtmlUnit as the built-in browser. HtmlUnit is 100% Java. This means there is a single GWT distribution for linux, mac, and windows, and debugging GWT Tests in development mode can be done entirely in a Java debugger.

Looks like Xmas has come early. I've been working with the browser plugin for a little bit and it is just a joy to use. One down side, of course, is that Intellij 9.0 will be out of date re: GWT the day it is released.

Related posts:

1. Plugging Some Cool Tools
2. Grails and Google App Engine: Birthing Pains
3. Don’t be lazy, download a good browser
4. How Cool an App in 300 Lines or Less?
5. GWT 1.5: Get Ready to Fix All of Your JSNI that Uses long

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1. 

   Brilliant! The declarative UI’s are going to be a big time saver and as a developer I’d rather code a UI than drag and drop it.

   Some drag and drop UI builders generate too much background code I feel. (Unless of course the tool is really useful such as Interface Builder)

   The mail sample in release 1 of GWT 2.0 makes use of this feature.

   Any idea when they are thinking of releasing the tool?

   Comment by James Heggs, Tuesday, October 13, 2009 @ 3:14 am

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