Removing JSON elements with jackson

Question

I\'ve a particular JSON Node that corresponds to import org.codehaus.jackson.JsonNode, and not import org.codehaus.jackson.map.JsonNode.

[
    {
        \"g         


        

Answer 1

According to the JSONObject documentation, JSONObject implements Map.remove, which returns the value stored at that key. Use it like

JSONObject json = new JSONObject();
json.put("key", "value");
String str = (String)json.remove("key");

Answer 2

I recently came to this question because I had an unusual piece of JSON that I needed to remove an element of:

{
   "allan": { "score": 88 },
   "bill": { "score": 75 },
   "cassie": { "score": 96 },
   "warnings": [ { "name": "class_low_numbers", "message": "this class is has less than 10 students" }]
}

The first three elements represent a person and a respective score object. The last one "warnings", didn't match the score object and that's the one I wanted to remove.

Taking the rootNode as the starting JsonNode from gsteff's answer above, the way I found to remove this was to iterate through each of the nodes, adding an object mapped version of the node to a HashMap which was the desired return object that I wanted unless it was the "warnings" element:

HashMap<String, ScoreDetails> results = new HashMap<String, ScoreDetails>();

ObjectMapper mapper = new ObjectMapper();
mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

Iterator<Map.Entry<String, JsonNode>> fields = rootNode.fields();
while (fields.hasNext()) {
  Map.Entry<String, JsonNode> next = fields.next();
  if (!next.getKey().equals("warnings")) {
    results.put(
        next.getKey(), mapper.treeToValue(next.getValue(), ScoreDetails.class));
  }
}

return results;

Answer 3

ObjectMapper of Jackson gives solution with only few steps.

Save the json data in a file say 'data.json'. Copy following the code into a function without import statements and invoke the function. The resulting JSON will be written into a new file 'data1.json'.

import java.io.File;
import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
ObjectMapper objectMapper = new ObjectMapper();
        JsonNode jsonNode = objectMapper.readTree(new File("data.json"));
        for (JsonNode node : jsonNode) {
            ((ObjectNode)node).remove("familyName");
            ((ObjectNode)node).remove("middleName");
        }
        objectMapper.writeValue(new File("data1.json"), jsonNode);

Answer 4

The answer written by gsteff can be used too, but I thought an easier way was to use the object mapper to convert to JSONArray instead of JsonNode and go from there.

ObjectMapper mapper = new ObjectMapper();
String stringJsonArray = mapper.writeValueAsString(list);
JSONArray csvDatabindedtoBean = new JSONArray(stringJsonArray);
        JSONArray finalArray = new JSONArray();
for (int val = 0; val < csvDatabindedtoBean.length(); val++) {
            JSONObject finalObject = csvDatabindedtoBean.getJSONObject(val);
                finalObject.remove("familyName");
                finalObject.remove("middleName");

            }
            finalArray.put(finalObject);
        }

Answer 5

I haven't tested this, but I think something like this would do what you want:

import org.codehaus.jackson.node.ObjectNode;
// ...
for (JsonNode personNode : rootNode) {
    if (personNode instanceof ObjectNode) {
        ObjectNode object = (ObjectNode) personNode;
        object.remove("familyName");
        object.remove("middleName");
    }
}

You could also do this more efficiently using Jackon's raw parsing API, but the code would be a lot messier.

Answer 6

You can just create a new JSONObject, read all nodes except "familyName" and "middleName", then save them all to a new file. Here is an example. JSON.Simple Example – Read And Write JSON