Remove duplicate key and value from json in java

Question

I am mapping Object (i don't have control over) to jsonString, after mapping I get duplicate key-value pairs in the JSON, example

 {
 "id":"123",
 "email":"[email protected]",
 "UserName":"someOne",
 "EMAIL":"[email protected]"
 }

the duplicate is exactly the same except that it is in uppercase letters. I am trying to get a jsonInString format without the duplication. Something like this:

 {
 "id":"123",
 "email":"[email protected]",
 "UserName":"someOne"
 }

I have tried

String jsonInStringWithOutDuplication=mapper.enable(
    JsonParser.Feature.STRICT_DUPLICATE_DETECTION).writeValueAsString(users);

with no luck, any suggestions?

they are not duplicate, you need first to arrange your hashmap — Tal Avissar
– Tal Avissar, Commented Feb 9, 2018 at 12:30

Ján Halaša · Accepted Answer · 2018-02-09 12:21:40Z

1

If you don't find a way to configure the ObjectMapper to filter out duplicate attributes, you can serialize the problematic object to JSON, then serialize the JSON to a Map object, merge duplicate attributes and serialize it to JSON again:

Map<String, String> objectWithDuplicates = new HashMap<>();
map.put("name", "MyName");
map.put("email", "em@ail");
map.put("EMAIL", "em@ail");

ObjectMapper mapper = new ObjectMapper();

String jsonWithDuplicates = mapper.writeValueAsString(objectWithDuplicates);
Map<String, Object> attributesWithDuplicates = mapper
        .readValue(jsonWithDuplicates, Map.class);

Map<String, Object> withoutDuplicates = new HashMap<>();
attributesWithDuplicates.forEach((key, value) -> {
    if (! withoutDuplicates.containsKey(key.toLowerCase())) {
        withoutDuplicates.put(key.toLowerCase(), value);
    }
});
String json = mapper.writeValueAsString(withoutDuplicates);

answered Feb 9, 2018 at 12:21

Ján Halaša

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1 Comment

Ipkiss Over a year ago

Thank you @JánHalaša that helped.

SaWo · Accepted Answer · 2018-02-08 15:15:48Z

0

Jackson's ObjectMapper has a feature that puts the same keys into an array. Isn't it something that could help you?

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new GuavaModule());
objectMapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);    
Multimap resultAsMultimap = mapper.readValue(json, Multimap.class);
System.out.println(resultAsMultimap);

answered Feb 8, 2018 at 15:15

SaWo

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