How to wrap JSON object to single-element array in Java

Question

I have a class in Java that I want to convert to JSON. The server which accepts this input expects a single-element JSON array, containing a key-value map

For instance, if you have a class as shown:

public class Input {

    private String id1;
    private int id2;
    private String s1;
    private String s2;
    private String s3;
    ...
}

// Code which converts above class to JSON string:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true);
Input input = new Input(id1, id2, s1, s2, s3);
System.out.println(objectMapper.writeValueAsString(input));

// Actual Output:
{"id1":"...","id2":...,"s1":"c...","s2":"...","s3":"..."}

// Expected Output:
[{"id1":"...","id2":...,"s1":"c...","s2":"...","s3":"..."}]

Any idea how to get the 'Expected Output'?

System.out.println(objectMapper.writeValueAsString(new Object[] { input })); => It looks like this does the trick! — Jared, Nov 16 '20 at 15:51
@Jared Instead of `new Object[] { input }` you can also use `Collections.singletonList(input)`. — Ivar, Nov 16 '20 at 15:55

score 0 · Answer 1 · answered Nov 16 '20 at 15:48

0

You can put your JSONObject into JSONArray like shown below.

JSONObject obj = new JSONObject();
obj.put("firstName", firstName);
obj.put("lastName", lastName);

JSONArray array = new JSONArray();
array.put(obj)

answered Nov 16 '20 at 15:48

Himanshu Singh

2,117
1
5
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Vincent Mimoun-Prat · Answer 2 · 2020-11-17T12:11:34.663

0

Two ways to do that (given the poor question specs)

The ugly

System.out.println("[" + objectMapper.writeValueAsString(input) + "]");

The good

Input[] input = new Input[] { new Input(id1, id2, s1, s2, s3) };
System.out.println(objectMapper.writeValueAsString(input));

edited Nov 17 '20 at 12:11

answered Nov 16 '20 at 15:49

Vincent Mimoun-Prat

28,208
16
81
124

Thank you @Vincent Mimoun-Prat – Jared Nov 16 '20 at 15:55
3

I would highly discourage the first one, and the second one is invalid syntax. – Andreas Nov 16 '20 at 16:04
Fixed the syntax, my Java is rusty. Of course #1 is discouraged. – Vincent Mimoun-Prat Nov 17 '20 at 12:13

score 0 · Answer 3 · answered Nov 16 '20 at 15:52

0

One way to do this is:

System.out.println(objectMapper.writeValueAsString(new Object[] { input }));

answered Nov 16 '20 at 15:52

Jared

73
6

How to wrap JSON object to single-element array in Java

3 Answers3