GWTApp provides several features like: HTML templating and messaging at runtime without application recompiling, MetaField to auto bind and simulate annotation of RPC data fields, Strong typing in MVC, Modular structure in Maven.
Java2Script(J2S) provides an Eclipse Java to JavaScript compiler plugin and a JavaScript version of Eclipse SWT besides common utilities like java.lang.* and java.util.*. SWT-based RCP can be converted into RIA by using J2S.