GWT: working with JSON services

Question

It's not a very concrete question. I created a simple project with a help of this tutorial, it's really fine. All the GWT code samples related to JSON I saw so far seem to work with a JSON (or immitate this work with some mock-up JSON), that is retrieved and processed in GWT. I'm a newbie in GWT, and I wonder, what are the cases of interacting with services that return JSON (services are mentioned in the same tutorial) and what are the pros and cons of such interaction.

I thought about two options (well, service is an overloaded term):

• everything that is mentioned in these JSON GWT tutorials is about the third-party services, like GData and Yahoo! Web Services mentioned here, which would make sense, cause it's about retrieving some data and processing in the app,

• and the second option is about services, that are created within the confines of a project (and, if there are some cases, and definitely there are some, my question is about them).

It's probably can't be fully explained in the answer, so a link (or a few) would be appreciated. Thanks in advance.

Answer 1

Your question is really quite generic. But here are some pointers:

JSON is just a data interchange format similar to XML or Protocol Buffers or some other proprietary format.
They are necessary in modern web applications because the UI is entirely controlled by the javascript code running in the browser.
However the data that a web application presents to the user usually resides on the backend. In order to get the data from the backend to the frontend you have to use some data interchange format like JSON or XML.
The advantage of JSON is, that is fairly efficient compared to XML and well accepted.
As you mentioned there are third party services that rely on JSON. These are very useful when you want to include the services in your applications.
The biggest advantage of applying this service oriented approach to your own project is that you decouple your components (frontend and backend). By doing this you achieve following things:

• Make your services available to other (web-)applications and users because your service exposes a specific API/data exchange format that they can use.
• Easily replace or add another frontend (for example create a desktop application in addition to your GWT application) that can work with your data (display or modify).