unnamed json array into java

Question

I have the following string:

"[{\"type\":\"string\",\"value\":\"value1\",\"field\":\"label\"},
    {\"type\":\"string\",\"value\":\"value2\",\"field\":\"address_unique\"}]"

and I want to turn this into java GSON JsonObject array/list in order to invoke something like:

myJsonObjs[i].getAsJsonPrimitive("value").getAsString();

What is the shortest path to achieve this? I tried setting up a bean like this:

public static class Filter {
    @SerializedName("type")
    private String type;
    @SerializedName("value")
    private String value;
    @SerializedName("field")
    private String field;

    //getters, setters and ctor
}

but I cannot find a way to deserialize the string above into an array/list of this bean using JsonParser or Gson. In particular I tried

Gson gson = new Gson();
gson.fromJson(json_string, Filter[].class);

(where json_string is the string above) but this gives me a

IllegalStateException: Expected BEGIN_ARRAY but was STRING

Thank you for your help!

Have you tried a list: gson.fromJson(json_string, new TypeToken<List<Filter>>(){}.getType())? — Ian Roberts
– Ian Roberts, Commented Jan 7, 2013 at 23:29
That gives the same ex: IllegalStateException: Expected BEGIN_ARRAY but was STRING... — matteo rulli
– matteo rulli, Commented Jan 8, 2013 at 7:14
Ok, I'm a silly guy: it was an escaping problem... Doing json_string.replace("\\","").replace("\"[", "[").replace("]\"","]"); solved the problem... Thanks! — matteo rulli
– matteo rulli, Commented Jan 8, 2013 at 8:23

Perception · Accepted Answer · 2013-01-07 23:36:18Z

4

Here is one way of doing it:

final String json = "[{\"type\":\"string\",\"value\":\"value1\",\"field\":\"label\"},{\"type\":\"string\",\"value\":\"value2\",\"field\":\"address_unique\"}]";
final JsonParser parser = new JsonParser();
final JsonElement rootElement = parser.parse(json);
final JsonArray values = rootElement.getAsJsonArray();
for (final JsonElement value : values) {
    final JsonObject obj = value.getAsJsonObject();
    final Filter filter = new Filter();
    filter.setType(obj.get("type"));
    filter.setValue(obj.get("value"));
    filter.setField(obj.get("field"));
}

And here is a more automated way:

final String json = "[{\"type\":\"string\",\"value\":\"value1\",\"field\":\"label\"},{\"type\":\"string\",\"value\":\"value2\",\"field\":\"address_unique\"}]";
final TypeToken<List<Filter>> token = new TypeToken<List<Filter>>() {
};
final Gson gson = new Gson();
final List<Filter> values = gson.fromJson(json, token.getType());

edited Jan 7, 2013 at 23:36

answered Jan 7, 2013 at 23:28

Perception

80.8k19 gold badges190 silver badges197 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

matteo rulli Over a year ago

Well, while reading your answer I realized I have a couple of " I should get rid of. In particular json_string.replace("\\","").replace("\"[", "[").replace("]\"","]");. With that your answer works great! Thanks...

palako · Accepted Answer · 2013-01-07 23:14:00Z

1

What have you tried with parse? What you have there is a string, you need two steps

parse the string into a JsonArray
Convert the JsonArray to the java object with fromJson

answered Jan 7, 2013 at 23:14

palako

3,5102 gold badges26 silver badges34 bronze badges

Comments

eugen · Accepted Answer · 2013-01-08 00:38:38Z

0

This looks strange, your code should work... Anyway you could also try Genson library, it has similar features to Gson plus some others and better performances.

Here is how to achieve it with Genson:

Genson genson = new Genson();
Filter[] filters = genson.deserialize(json, Filter[].class);

// or if you need a list
List<Filter> filters = genson.deserialize(json, new GenericType<List<Filter>>(){});

answered Jan 8, 2013 at 0:38

eugen

5,9162 gold badges31 silver badges26 bronze badges

Comments

Ray · Accepted Answer · 2015-07-10 16:36:46Z

0

it can be first parsed into an array, then converted to a list.

final Gson gson = new Gson();
final Filter[] values = gson.fromJson(json, Filter[].class);
ArrayList< Filter > filterList = new ArrayList< Filter >(Arrays.asList(values));

answered Jul 10, 2015 at 16:36

Ray

16.3k5 gold badges34 silver badges52 bronze badges

Collectives™ on Stack Overflow

unnamed json array into java

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related