Make Jackson interpret single JSON object as array with one element

Question

Is there a way to make Jackson interpret single JSON object as an array with one element and vice versa?

Example, I have 2 slightly different formats of JSON, I need both to map to same Java object:

Format A (JSON array with one element):

points : [ {
    date : 2013-05-11
    value : 123
}]

Format B (JSON object, yes I know it looks "wrong" but it's what I'm given):

points : {
    date : 2013-05-11
    value : 123
}

Target Java object that both of the above should convert to:

//Data.java 
public List<Point> points;
//other members omitted

//Point.java
class Point {
    public String date;
    public int value;
}

Currently, only A will parse properly to Data. I want avoid directly tampering with the JSON itself. Is there some configuration in Jackson I can tamper with in order to make it accept B ?

Michał Ziober · Accepted Answer · 2019-11-25T09:00:32.137

90

Try with DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY - it should work for you.

Example:

final String json = "{\"date\" : \"2013-05-11\",\"value\" : 123}";

final ObjectMapper mapper = new ObjectMapper()
        .enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
final List<Point> points = mapper.readValue(json,
        new TypeReference<List<Point>>() {});

edited Nov 25 '19 at 09:00

answered Jun 08 '13 at 22:54

Michał Ziober

37,175
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1

Looks to be exactly what I'm looking for. I'll try this out tomorrow. Thanks. – XiaoChuan Yu Jun 09 '13 at 23:17
It doesn't exist in Jackson 1.7.9. What is the relationship between that and the link you sent? – David Brossard May 16 '14 at 14:41
1

You should upgrade `Jackson` library to at least version `2.x.x`. – Michał Ziober May 16 '14 at 21:26
8

It is also possible to enable it on a per-field basis, using @JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY) – Magnus Reftel May 22 '20 at 13:24

score 9 · Answer 2 · answered May 29 '14 at 21:40

The Jackson 1.x-compatible version uses DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY. So the above answer changes to:

final String json = "{\"date\" : \"2013-05-11\",\"value\" : 123}";

final ObjectMapper mapper = new ObjectMapper()
    .enable(DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY);
final List<Point> points = mapper.readValue(json,
    new TypeReference<List<Point>>() {
    });
System.out.println(points);

score 0 · Answer 3 · answered Aug 24 '18 at 06:50

Can solve the above problem by this code is given below, this works

 final ObjectMapper objectMapper = new 
 ObjectMapper().enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);

 objectMapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
 try {
      String jsonInString = objectMapper.writeValueAsString(products.get(j));
      InventoryParser inventoryParser = objectMapper.readValue(jsonInString, 
                                       InventoryParser.class);

      System.out.println(inventoryParser.getId());

     } 
     catch (IOException e) 
     {
       e.printStackTrace();
     }

"InventoryParser" is a POJO Class. "products.get(j)" is JSON String.

Make Jackson interpret single JSON object as array with one element

3 Answers3

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