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 · 2019-11-25 09:00:32Z

95

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, 2019 at 9:00

answered Jun 8, 2013 at 22:54

Michał Ziober

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4 Comments

XiaoChuan Yu Over a year ago

Looks to be exactly what I'm looking for. I'll try this out tomorrow. Thanks.

David Brossard Over a year ago

It doesn't exist in Jackson 1.7.9. What is the relationship between that and the link you sent?

Michał Ziober Over a year ago

You should upgrade Jackson library to at least version 2.x.x.

Magnus Reftel Over a year ago

It is also possible to enable it on a per-field basis, using @JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY)

phillipuniverse · Accepted Answer · 2014-05-29 21:40:13Z

9

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);

answered May 29, 2014 at 21:40

phillipuniverse

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Comments

S Mugunthan kumar · Accepted Answer · 2018-08-24 06:50:08Z

0

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.

answered Aug 24, 2018 at 6:50

S Mugunthan kumar

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