How read json file, and convert it to POJO using GSON

Question

I need to pass values from a json file to a java class,the json file is like this exemple:

    {
        "id":1,
        "name":"Gold",
        "description":"Shiny!",
        "spriteId":1,
        "consumable":true,
        "effectsId":[1]
    },

i need to map,i did this:

Items i = new Items();


Map<String, Items> mapaNomes = new HashMap<String, Items>();
mapaNomes.put("Gold",i);
mapaNomes.put("Apple",i );
mapaNomes.put("Clain Mail",i );

I'm new to android Development and I'm probably forgetting something because the following is not working,someone can help in find what`s is wrong?

BufferedReader in  = new BufferedReader(new InputStreamReader(System.in));

Gson gson = new Gson(); 
Items Items = gson.fromJson((BufferedReader) mapaNomes, Items.class);

Why are you casting a Map to a BufferedReader which has nothing to do with the json? — Lawrence Choy
– Lawrence Choy, Commented Oct 23, 2015 at 1:29
DataObject obj = gson.fromJson(br, DataObject.class); first convert your json reponse to DataObject and then map it. here br is BufferedReader object — Susheel Singh
– Susheel Singh, Commented Oct 23, 2015 at 1:34

Fadils · Accepted Answer · 2015-10-24 04:11:33Z

1. Create your POJO representation for your Json.

public class MapaNomes() {
    String name;
    String description;
    // etc

    public String getName() {
        return name;
    }

    // create your other getters and setters
}

I find this tool is handy for transforming json to POJO. http://www.jsonschema2pojo.org/

2. Read your file.json. Turn it into object

JsonReader reader = new JsonReader(new FileReader("file.json"));
MapaNomes mapaNomes = new Gson().fromJson(reader, MapaNomes.class);

Bonus

I'm thinking that there might be numerous json objects in your file.json such as:

{
    "id":1,
    "name":"Gold",
    "description":"Shiny!",
    "spriteId":1,
    "consumable":true,
    "effectsId":[1]
},
...
{
    "id":999,
    "name":"Silver",
    "description":"Whatever!",
    "spriteId":808,
    "consumable":true,
    "effectsId":[2]
},

If this is the case, then you can do the following:

JsonReader reader = new JsonReader(new FileReader("file.json"));
List<MapaNomes> mapaNomeses = new Gson().fromJson(
                                reader, 
                                new TypeToken<List<Review>>() {}.getType());

Then you can do whatever you want with each and every one of them

for (MapaNomes mapaNomes : mapaNomeses) {
    // whatever
}

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How read json file, and convert it to POJO using GSON

1 Answer 1

1. Create your POJO representation for your Json.

2. Read your file.json. Turn it into object

Bonus

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Collectives™ on Stack Overflow

1 Answer 1

1. Create your POJO representation for your Json.

2. Read your file.json. Turn it into object

Bonus

Comments

Your Answer

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