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Using GSON to deserialize a JSON String

Vasilis Souvatzis
Ranch Hand

Joined: Mar 23, 2014
Posts: 43

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
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Joined: Mar 17, 2011
Posts: 8247
    
  23

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.

HIH

Winston

Isn't it funny how there's always time and money enough to do it WRONG?
Articles by Winston can be found here
Bear Bibeault
Author and ninkuma
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Joined: Jan 10, 2002
Posts: 61658
    
  67

List are tricky. I've had luck with:


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Vasilis Souvatzis
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Joined: Mar 23, 2014
Posts: 43

*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...
 
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