Simply Java
ZK is renowned for its "Ajax without JavaScript" approach since 2005, enabling developers to build rich Internet applications transparently in pure Java.
The client engine and update engine in ZK play the roles of pitcher and catcher, rendering Ajax communication transparent to developers. Events triggered by users are encapsulated and marshaled to event listeners running at the server.
User interface rendered on browsers are surrogated on the server as POJO components, alternation made on the POJO components are reflected to the client transparently.
With programs executed at the server, developers can leverage all the Java technologies, such as Java EE and Spring, while back-end data and services are readily available.