5 GWT 2.5 new features

2.5 Features

1. Super Dev Mode (experimental)
2. Elemental (experimental)
3. New compiler optimizations
4. Updated ARIA support
5. UIBinder Enhancements
6. Validation Enhancement

Super Dev Mode (experimental)

Super Dev Mode is an experimental replacement for Development Mode.

Elemental (experimental)

Elemental is an experimental new library for fast, lightweight, and "to the metal" web programming in GWT. It's intended for developers who are comfortable working with the browser API's that JavaScript programmers use.

New compiler optimizations
The GWT compiler can optionally use the Closure compiler to provide additional JavaScript optimizations. The Closure compiler has a collection of Javascript optimizations that can benefit code size, including a graph-coloring-based variable allocator, comprehensive JavaScript function and variable inlining, cross-module code motion, statement fusing, name shadowing and many more. However, this makes the GWT compiler slower, so it's not enabled by default. Simply add the -XenableClosureCompiler to the list of compiler flags to enable optimization.
Large projects that use Code Splitting and have many split points can take advantage of Fragment Merging. The GWT compiler can automatically merge fragments to reduce the size of the "leftover" fragment.

Updated ARIA support

Added a new accessibility ARIA library that has a full coverage of the W3C ARIA standard. This makes it easier to correctly set ARIA roles, states, and properties on DOM elements. 

UIBinder Enhancements

GWT 2.5 adds extensions to UiBinder that allow it to support Cell rendering and event handling. In particular, this design enables UiBinder to generate a UiRenderer implementation to assist with rendering SafeHtml, and dispatching events to methods specified by @UiHandler tags. Also introduced the IsRenderable/RenderablePanel types. When used by an application instead of HTMLPanel, they can significantly improve rendering time and reduce the latency of complex UiBinder UIs.

Validation Enhancements

GWT 2.5 adds support for more features of JSR-303 Bean Validation specification and this support is no longer considered "experimental".