GWT uses remote procedure calls (RPC) to pass data to and from the web server. Typically, the RPC calls are handled by a server-side Java application tightly integrated with the GWT application – passing serialized Java objects back and forth. However, in this case, we are not using any Java inside the device. Instead, the server-side RPC is implemented as a CGI in C and passes data in the form of JSON objects.
Advantages to using GWT in devices:
- No resources wasted spawning scripts or formatting HTML for each page
- Data passed to and from device via well-formed JSON-RPC only
- Lightweight - shifting the workload to the browser instead of the device
- More secure than using shell scripts and parsing query string input
Perhaps one of the only drawbacks is the size of the GWT produced content. Uncompressed, an application of about 1300 lines of Java code compiles to a size of more than half a megabyte. When compressed, this goes down to around 250K. For some devices, this could be a show stopper. The GWT application is just static content, but the application must be downloaded from the same source as the RPC callbacks to work in a browser. Though, what about a desktop application? Looking forward to the Adobe Apollo project to see if the same GWT content can be dropped into a desktop application while still interfacing with and configuring devices using JSON-RPC.