Runtime Library Support
GWT supports only a small subset of the classes available in the Java 2
Standard and Enterprise Edition libraries, as these libraries are quite
large and rely on functionality that is unavailable within web
browsers. To find out exactly which classes and methods are supported
for core Java runtime packages, see the API reference for
java.lang and
java.util, which lists supported
classes and contains notes on behavioral differences from the standard
Java runtime.
Some specific areas in which GWT emulation differs from the standard
Java runtime:
-
Regular Expressions
-
Serialization
Java serialization
relies on a few mechanisms that are not available in compiled
JavaScript, such as dynamic class loading and reflection. As a result,
GWT does not support standard Java serialization. Instead, GWT has an
RPC facility that provides
automatic object serialization to and from the server for the purpose
of invoking remote methods.
Tip
You'll save yourself a lot of frustration if you make sure that
you use only translatable classes in your
client-side code
from the very beginning. To help you identify problems early, your
code is checked against the JRE emulation library whenever you run
in
hosted mode. As
a result, most uses of unsupported libraries will be caught the
first time you attempt to run your application. So,
run early
and often.
