It’s not possible to use Javadoc as html files in eDesigner. The javadoc only works when the source code (with javadoc) is available. Thus, to extend Javadoc, you need to integrate the source code in a library (jar) and copy the source code in the following directory of edesigner:
edesigner\jdk\src
The source code of the Java virtual machine is available and certainly only used for the javadoc. If for example you add the Avintis framework, the javadoc will be available. Because the eways sources aren't available, it's not possible to have the javadoc of the connectors in eDesigner.