Deserialization – Read JSON using Gson. Deserialization in the context of Gson means converting a JSON string to an equivalent Java object. In order to do the deserialization, we need a Gson object and call the function fromJson() and pass two parameters i.e. JSON string and expected java type after parsing is finished ...
Gson can serialize a collection of arbitrary objects but can't deserialize the data without additional information. That's because there's no way for the user to indicate the type of the resulting object. Instead, while deserializing, the Collection must be of a specific, generic type.
Introduction. Gson is the main actor class of Google Gson library. It provides functionalities to convert Java objects to matching JSON constructs and vice versa. Gson is first constructed using GsonBuilder and then toJson(Object) or fromJson(String, Class) methods are used to read/write JSON constructs.
With Gson, you'd just need to do something like:
List<Video> videos = gson.fromJson(json, new TypeToken<List<Video>>(){}.getType());
You might also need to provide a no-arg constructor on the Video
class you're deserializing to.
Another way is to use an array as a type, e.g.:
Video[] videoArray = gson.fromJson(json, Video[].class);
This way you avoid all the hassle with the Type object, and if you really need a list you can always convert the array to a list, e.g.:
List<Video> videoList = Arrays.asList(videoArray);
IMHO this is much more readable.
In Kotlin this looks like this:
Gson().fromJson(jsonString, Array<Video>::class.java)
To convert this array into List, just use .toList()
method
I recomend this one-liner
List<Video> videos = Arrays.asList(new Gson().fromJson(json, Video[].class));
Warning: the list of videos
, returned by Arrays.asList
is immutable - you can't insert new values. If you need to modify it, wrap in new ArrayList<>(...)
.
Reference:
json
may be of type JsonElement
, Reader
, or String
)Be careful using the answer provide by @DevNG. Arrays.asList() returns internal implementation of ArrayList that doesn't implement some useful methods like add(), delete(), etc. If you call them an UnsupportedOperationException will be thrown. In order to get real ArrayList instance you need to write something like this:
List<Video> = new ArrayList<>(Arrays.asList(videoArray));
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