Parse different JSON responses without using POJO classes in Java

Question

I am parsing JSON responses from the REST API in Java, but I do not want to create a Java class (POJO) for each answer (the answers have different data structures and fields). Is there a more general JSON parser in Java that looks like simple JavaScript syntax?

The JSON below is the result of only one of the many REST endpoints

{
    "f1" : "volume",
    "f2" : "gender",
    "f3" : "days",
    "f4" : [{
            "id" : "F",
            "name" : "female",
            "values" : [{
                    "name" : "September",
                    "value" : 12
                }
            ]
        }, {
            "id" : "M",
            "name" : "male",
            "values" : [{
                    "name" : "September",
                    "value" : 11
                }
            ]
        }
    ]
}

In JavaScript, to access a value for a woman:

jsonRoot.f4[0].values[0].value

which is tidier than creating many Java classes. Can you suggest something like this or a way to avoid creating many POJOs?

Answer 1

com.google.gson. :

     String str="{" +
            "    \"f1\" : \"volume\"," +
            "    \"f2\" : \"gender\"," +
            "    \"f3\" : \"days\"," +
            "    \"f4\" : [{" +
            "            \"id\" : \"F\"," +
            "            \"name\" : \"female\"," +
            "            \"values\" : [{" +
            "                    \"name\" : \"September\"," +
            "                    \"value\" : 12" +
            "                }" +
            "            ]" +
            "        }, {" +
            "            \"id\" : \"M\"," +
            "            \"name\" : \"male\"," +
            "            \"values\" : [{" +
            "                    \"name\" : \"September\"," +
            "                    \"value\" : 11" +
            "                }" +
            "            ]" +
            "        }" +
            "    ]" +
            "}";
    JsonParser parser=new JsonParser();
    JsonObject object=(JsonObject)parser.parse(str);
    String value=object.get("f4").getAsJsonArray().get(0).getAsJsonObject()
            .get("values").getAsJsonArray().get(0).getAsJsonObject()
            .get("value").getAsString();

Answer 2

    String s="[0,{\"1\":{\"2\":{\"3\":{\"4\":[5,{\"6\":7}]}}}}]";
    Object obj=JSONValue.parse(s);
    JSONArray array=(JSONArray)obj;
    System.out.println(array.get(1));       
    System.out.println(((JSONObject)array.get(1)).get("1"));

json-simple.jar

Answer 3

Map<String, Object> :

    String data = "{\"f4\":[1, 2]}"

    try {
        Map<String, Object> value = mapper.readValue(data, Map.class);
        System.out.println(value.get("f4"));
    } catch (IOException e) {
        e.printStackTrace();
    } 

POJO - , .

Answer 4

org.json.

maven:

    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20150729</version>
    </dependency>

: http://mvnrepository.com/artifact/org.json/json

Java:

import org.json.JSONObject;

public class JSONTest {

    public static void main(String[] args) {

        JSONObject jsonObject = new JSONObject("{'f1' : 'volume', 'f2' : 'gender', 'f3' : 'days'}"); // Truncated for example purpose

        String f1 = jsonObject.getString("f1");
        System.out.println(f1);
    }
}

JSONArray f4Array = jsonObject.getJSONArray("f4");

.

for (int i = 0; i < f4Array.length(); i++){
        String id = f4Array.getJSONObject(i).getString("id");
        String name = f4Array.getJSONObject(i).getString("name");
        System.out.println(name);
        System.out.println(id);
        JSONArray values = f4Array.getJSONObject(i).getJSONArray("values");
        for (int j = 0; j < values.length(); j++){
            String dName = values.getJSONObject(j).getString("name");
            int dValue = values.getJSONObject(j).getInt("value");
            System.out.println(dName);
            System.out.println(dValue);
        }

    }

Answer 5

parseJson() JQuery, jQuery.