Grouping same date JSON data together Using java

Question

I have created one json Object Using java and it's values are given below

{
  "result":[
    {"ID":7252,"Age":52,"Date":"2015-11-25","DAY":"Wednesday","Gender":"M"},
    {"ID":7252,"Age":52,"Date":"2015-12-05","DAY":"Saturday","Gender":"M"},
    ....
  ],
  "status":"ok"
}

I need to group data as per date,required format is given below

{
  "result":[
    {"2015-11-25":[
      {"ID":7252,"Age":52,"Date":"2015-11-25","DAY":"Wednesday","Gender":"F"},
      {"ID":7252,"Age":52,"Date":"2015-11-25","DAY":"Wednesday","Gender":"M"}
    ]},
    {"2015-10-25":[
      {"ID":7252,"Age":52,"Date":"2015-10-25","DAY":"Tuesday","Gender":"F"},
      {"ID":7252,"Age":52,"Date":"2015-10-25","DAY":"Tuesday","Gender":"M"}
    ]},
  ],
  "status":"ok"
}

Basically i need group all same date data together inside JSON with date as key How can i achieve this JSON format using java

Benjamin M · Accepted Answer · 2016-06-04 13:01:59Z

4

What kind of JSON mapper do you use? Jackson, GSON, ...?

And please provide some code. So we can see what you're doing.

If you created the JSON object using Java, you should have a Java Object structure, right?

Something like this:

class Data {
  int id;
  int age;
  LocalDate date;
  ...
}

And somewhere an Array / List of your data:

List<Data> result = new ArrayList<>();
result.add(data1);
result.add(data2);
result.add(data3);

Then you can use Java8 Stream API to group your data:

Map<LocalDate, Data> grouped = result
    .stream()
    .collect(
        Collectors.groupingBy(Data::getDate)
    );

The result will be a Map. Your result should be a List.

So you should be able to simply iterate over the Map and insert it into a new List.

edited Jun 4, 2016 at 13:01

answered Jun 4, 2016 at 12:50

Benjamin M

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Comments

Raymond Choi · Accepted Answer · 2023-02-17 19:42:18Z

You can use JSON library such as Josson to do the transformation.

https://github.com/octomix/josson

Josson josson = Josson.fromJsonString(
    "{" +
    "  \"result\":[" +
    "    {\"ID\":7252,\"Age\":52,\"Date\":\"2015-11-25\",\"DAY\":\"Wednesday\",\"Gender\":\"M\"}," +
    "    {\"ID\":7252,\"Age\":52,\"Date\":\"2015-12-05\",\"DAY\":\"Saturday\",\"Gender\":\"M\"}," +
    "    {\"ID\":7252,\"Age\":52,\"Date\":\"2015-11-25\",\"DAY\":\"Wednesday\",\"Gender\":\"F\"}," +
    "    {\"ID\":7252,\"Age\":52,\"Date\":\"2015-12-05\",\"DAY\":\"Saturday\",\"Gender\":\"F\"}" +
    "  ]," +
    "  \"status\":\"ok\"" +
    "}");
JsonNode node = josson.getNode("field(result.group(Date).map(Date::elements))");
System.out.println(node.toPrettyString());

Output

{
  "result" : [ {
    "2015-11-25" : [ {
      "ID" : 7252,
      "Age" : 52,
      "Date" : "2015-11-25",
      "DAY" : "Wednesday",
      "Gender" : "M"
    }, {
      "ID" : 7252,
      "Age" : 52,
      "Date" : "2015-11-25",
      "DAY" : "Wednesday",
      "Gender" : "F"
    } ]
  }, {
    "2015-12-05" : [ {
      "ID" : 7252,
      "Age" : 52,
      "Date" : "2015-12-05",
      "DAY" : "Saturday",
      "Gender" : "M"
    }, {
      "ID" : 7252,
      "Age" : 52,
      "Date" : "2015-12-05",
      "DAY" : "Saturday",
      "Gender" : "F"
    } ]
  } ],
  "status" : "ok"
}

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