How to turn a list of json Strings into one JsonNode/Object in java

Question

I have some data that is put into a List and I am trying to use the ObjectMapper class from Jackson to map them into a single string so that I can then convert them into a JsonNode to return. The issue is that I do not want to manually hardcode commas for the mapper to distinguish each element.

The list returned from the database looks like this:

0: {"someKey": "someVal"}
1: {"someKey2": "someVal2"}
2: {"someKey3": "someVal3"}

List<String> responseList = dao.getDetails(something, something2);

for(String row : responseList){
 responseString += row;
}

jsonNode = mapper.readTree(responseString);

The resulting jsonNode of that would be :

{"someKey": "someVal"}

the objectmapper ignores the other two values because the string doesn't have any commas to distinguish them. How can I get a single JsonNode response for a list of strings without having to manually insert commas and brackets? thanks!!

Wai Ha Lee · Accepted Answer · 2021-10-22 11:42:25Z

4

Instead of joining everything into a String, you can parse individually each row and add it manually to an ArrayNode, like this:

List<String> responseList = Arrays.asList(
        "{\"someKey\": \"someVal\"}",
        "{\"someKey2\": \"someVal2\"}",
        "{\"someKey3\": \"someVal3\"}");

ObjectMapper mapper = new ObjectMapper();
ArrayNode arr = mapper.createArrayNode();
for (String row : responseList) {
    arr.add(mapper.readTree(row));
}
System.out.println(arr);

edited Oct 22, 2021 at 11:42

Wai Ha Lee

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answered Oct 22, 2021 at 1:08

Pablo Matias Gomez

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