my dog learned polymorphism
The moose likes Other Open Source Projects and the fly likes Using GSON to deserialize a JSON String Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login
JavaRanch » Java Forums » Products » Other Open Source Projects
Bookmark "Using GSON to deserialize a JSON String" Watch "Using GSON to deserialize a JSON String" New topic

Using GSON to deserialize a JSON String

Vasilis Souvatzis
Ranch Hand

Joined: Mar 23, 2014
Posts: 69

Man I thought it'd be easy to use GSON, apparently it isn't as easy to deserialize a JSON String as it is to serialize...

Let me guide you through the process; i'm making a dieting app for a friend of mine and I'm using JSON to store the diets, later I'll use them to create HTML reports and such. In my GUI's controller, I have a DietSchedule object that gets initialized as such:

From what I've read online, the problem is that the types collections hold, do not get "saved" or something along these lines, I don't have much experience with generics and (de)serialization. I believe there is a solution to this (from what I've read) but I'm too much of a noob to understand it or know where to fix it in my code.

In my controller I'm using ObservableLists (JavaFX8), so I thought it would be better to use List in the MealLists since it's a supertype and thus would accept every sub-type.

I'm attaching the basics of my classes, any help would be greatly appreciated (I don't want to save to XML instead of JSON, XML is more difficult to handle than JSON in HTML [according to a friend of mine that is]).

Netbeans 8.0.1 - JavaEE 7 - Glassfish 4.1
Winston Gutkowski

Joined: Mar 17, 2011
Posts: 8942

Vasilis Souvatzis wrote:Man I thought it'd be easy to use GSON...

There's a LOT of stuff in that post, which leads me to suspect that you're flapping around for a solution.

I'm no GSON or JSON expert, but the first thing I would do is to break the problem down.

And the first thing is, does:
DietSchedule schedule = gson.fromJson(jsonContents, DietSchedule.class);
return you anything?

If not, THAT'S what you need to tackle. Forget what you want to do with it, just make sure that you can get ONE DietSchedule object as you want it. EVERY TIME. Once you have that, everything else is Java.



Bats fly at night, 'cause they aren't we. And if we tried, we'd hit a tree -- Ogden Nash (or should've been).
Articles by Winston can be found here
Bear Bibeault
Author and ninkuma

Joined: Jan 10, 2002
Posts: 63858

List are tricky. I've had luck with:

[Asking smart questions] [About Bear] [Books by Bear]
Vasilis Souvatzis
Ranch Hand

Joined: Mar 23, 2014
Posts: 69

*sigh* I fixed it... It had nothing to do with JSON after all...

Bear I appreciate your code snippet and I'll keep it for future reference, but it was Winston that indirectly gave me the solution

In my MealLists class I had List sth when it should have been List<Food> sth!!! No surprise it didn't work, I was using Generics when I shouldn't since I know exactly what class objects my lists hold.

So after I changed that code bit, everything works like a charm It wasn't GSON, it wasn't JSON, it was pure Java and it was my bad...
I agree. Here's the link:
subject: Using GSON to deserialize a JSON String
It's not a secret anymore!