@Documented
@Retention(value=RUNTIME)
@Target(value=FIELD)
public @interface GwtTransient

This annotation means the same thing as the transient keyword, but it is ignored by all serialization systems other than GWT's. Usually the transient keyword should be used in preference to this annotation. However, for types used with multiple serialization systems, it can be useful.

Note that GWT will actually accept any annotation named GwtTransient for this purpose. This is done to allow libraries to support GWT serialization without creating a direct dependency on the GWT distribution.