Parsing JSON array into java.util.List with Gson

java json parsing gson
Abel Callejo picture Abel Callejo · Aug 31, 2013 · Viewed 186.3k times · Source

I have a JsonObject named "mapping" with the following content:

{
    "client": "127.0.0.1",
    "servers": [
        "8.8.8.8",
        "8.8.4.4",
        "156.154.70.1",
        "156.154.71.1"
    ]
}

I know I can get the array "servers" with:

mapping.get("servers").getAsJsonArray()

And now I want to parse that JsonArray into a java.util.List...

What is the easiest way to do this?

Answer

MikO picture MikO · Aug 31, 2013

Definitely the easiest way to do that is using Gson's default parsing function fromJson().

There is an implementation of this function suitable for when you need to deserialize into any ParameterizedType (e.g., any List), which is fromJson(JsonElement json, Type typeOfT).

In your case, you just need to get the Type of a List<String> and then parse the JSON array into that Type, like this:

import java.lang.reflect.Type;
import com.google.gson.reflect.TypeToken;

JsonElement yourJson = mapping.get("servers");
Type listType = new TypeToken<List<String>>() {}.getType();

List<String> yourList = new Gson().fromJson(yourJson, listType);

In your case yourJson is a JsonElement, but it could also be a String, any Reader or a JsonReader.

You may want to take a look at Gson API documentation.

Related questions

"Expected BEGIN_OBJECT but was STRING at line 1 column 1"

I have this method: public static Object parseStringToObject(String json) { String Object = json; Gson gson = new Gson(); Object objects = gson.fromJson(object, Object.class); parseConfigFromObjectToString(object); return objects; } And I want to parse a JSON with: public static void addObject(…

Read More
Parse JSON file using GSON

I want to parse this JSON file in JAVA using GSON : { "descriptor" : { "app1" : { "name" : "mehdi", "age" : 21, "messages": ["msg 1","msg 2","msg 3"] }, "app2" : { "name" : "mkyong", "age" : 29, "messages": ["msg 11","msg 22","msg 33"] }, "app3" : { "name" : "amine", "age" : 23, "messages": ["msg 111","msg 222","msg 333"] } } } but I don't know …

Read More
GSON - Get JSON value from String

I trying to parse the JSON String "{'test': '100.00'}" and to get the value: 100.00 with the GSON library. My code looks like this: String myJSONString = "{'test': '100.00'}"; JsonObject jobj = new Gson().fromJson(myJSONString, JsonObject.class); String result = jobj.…

Read More