How to parse JSON to list of strings?

Question

I have a json file.

{
    "data" : [
        "my/path/old",
        "my/path/new"
    ]
}

I need to conver it to ArrayList of String. How to do it using Jackson library?

UPD:

My code:

Gson gson = new Gson();        
JsonReader reader = new JsonReader(new InputStreamReader(FileReader.class.getResourceAsStream(file)));

List<String> list = (ArrayList) gson.fromJson(reader, ArrayList.class);

for (String s : list) {
    System.out.println(s);
}

And my exception:

Exception in thread "main" com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Expected value at line 1 column 1

My new update

UPD2:

Gson gson = new Gson();
Type list = new TypeToken<List<String>>(){}.getType();
JsonReader reader = new JsonReader(new InputStreamReader(FileReader.class.getResourceAsStream(file)));
List<String> s = gson.fromJson(reader, list);
System.out.println(s);

possible duplicate of How to convert the following json string to java object? — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Apr 4, 2014 at 21:42
Your JSON is an object, not an array. There's no obvious way to convert it to a List. Do you want the array named data? — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Apr 4, 2014 at 21:53

Sotirios Delimanolis · Accepted Answer · 2014-04-04 22:20:31Z

4

You've tagged Jackson but are using Gson in your example. I'm going to go with Jackson

String json = "{\"data\":[\"my/path/old\",\"my/path/new\"]}"; // or wherever you're getting it from

Create your ObjectMapper

ObjectMapper mapper = new ObjectMapper();

Read the JSON String as a tree. Since we know it's an object, you can cast the JsonNode to an ObjectNode.

ObjectNode node = (ObjectNode)mapper.readTree(json);

Get the JsonNode named data

JsonNode arrayNode = node.get("data");

Parse it into an ArrayList<String>

ArrayList<String> data = mapper.readValue(arrayNode.traverse(), new TypeReference<ArrayList<String>>(){});

Printing it

System.out.println(data);

gives

[my/path/old, my/path/new]

answered Apr 4, 2014 at 22:20

Sotirios Delimanolis

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1 Comment

Sotirios Delimanolis Over a year ago

@Flavio Are you sure your JSON is well formed? You might want to convert it to a String and print it out before passing it to your ObjectMapper. Also I was using Jackson 2. You might wish to upgrade.

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