Update value of a nested JSON in Java

Question

I have to work with the following pre-defined JSON request. This JSON is stored in a local file. I would like to update the values of a couple of elements ("level-4b-1" and "level-4b-3" > "StartDate") in the JSON and submit the request.

{
"level-1": {
  "level-2": {
     "level-3": {
        "level-4a": [
           "value-4a"
        ],
        "level-4b": [
           {
              "level-4b-1": "value-4b-1",
              "level-4b-2": "value-4b-2",
              "level-4b-3": {
                 "StartDate": "2017-11-13T00:00:00"
              }
           }
        ]
     },
     ...

I have the following code but I am not sure how to go deeper in a single line of code and then update the value.

    JSONParser parser = new JSONParser();
    Object requestFileObj = parser.parse(new FileReader(context.getRealPath(localJsonFile)));
    JSONObject requestJsonObject =  (JSONObject) requestFileObj;

    if (requestJsonObject instanceof JSONObject) {

        JSONObject level1 = (JSONObject)chartRequestJsonObject.get("level-1");

teppic · Accepted Answer · 2018-05-01 23:51:43Z

4

JsonPath provides a convenient way of addressing nodes in json documents. JayWay is a good java implementation.

With JayWay:

DocumentContext doc = JsonPath.parse(json);
doc.set("level-1.level-2.level-3.level-4b[0].level-4b-3.StartDate", Instant.now().toString());
System.out.println(doc.jsonString());

answered May 1, 2018 at 23:51

teppic

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1 Comment

pls Over a year ago

How did you managed to make it work? Tried your code but it's not working.

final Configuration configuration = Configuration.defaultConfiguration()             .addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL)             .addOptions(Option.SUPPRESS_EXCEPTIONS);          DocumentContext doc = JsonPath.parse("{}", configuration);         doc.set("level-1.level-2.level-3.level-4b[0].level-4b-3.StartDate", Instant.now().toString());         System.out.println(doc.jsonString());

pgngp · Accepted Answer · 2018-05-02 01:54:19Z

If you are open to using Google's JSON library (https://github.com/google/gson), you can update nested elements and save them as shown in the following sample code:

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonObject;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.io.IOException;
import java.io.FileReader;
import java.nio.file.StandardOpenOption;

public class JsonUpdater {
  // Method to update nested json elements
  public void updateJson(String inputFile, String outputFile) {
      try {
          // Get the json content from input file
          String content = new String(Files.readAllBytes(Paths.get(inputFile)));

          // Get to the nested json object
          JsonObject jsonObj = new Gson().fromJson(content, JsonObject.class);
          JsonObject nestedJsonObj = jsonObj
                  .getAsJsonObject("level-1")
                  .getAsJsonObject("level-2")
                  .getAsJsonObject("level-3")
                  .getAsJsonArray("level-4b").get(0).getAsJsonObject();

          // Update values
          nestedJsonObj.addProperty("level-4b-1", "new-value-4b-1");
          nestedJsonObj.getAsJsonObject("level-4b-3").addProperty("StartDate", "newdate");

          // Write updated json to output file
          Files.write(Paths.get(outputFile), jsonObj.toString().getBytes(), StandardOpenOption.CREATE);
      } catch (IOException exception) {
          System.out.println(exception.getMessage());
      }
  }

  // Main
  public static void main(String[] args) {
    JsonUpdater jsonUpdater = new JsonUpdater();
    jsonUpdater.updateJson("test.json", "new.json");
  }
}

The above code reads json string from test.json, updates the values for level-4b-1 and StartDate (within level-4b-3), and saves the updated json string into new.json.

This is by far an amazing solution! I was able to update some values of a JSON following this code. thank you!

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