How to use Jackson for parse object follow json type? - java-8

Question

I have two Json objects like :
Object 1
{
"value": {
"data": [
"John",
"Justin",
"Tom"
],
"isGraduated": false
}
}
Object 2
{
"value": {
"data": {
"info": {
"background": {
"primarySchool" : "A school",
"univeristy": "X univeristy"
},
"name": "John",
"gender": "male",
"dayOfBirth": "1995-04-24"
}
},
"isGraduated": false
}
}
How can I deserialize the data field to list of strings or class(I've already declared) by using Jackson?
Edit
Add class Info declaration.
public class Info {
#JsonProperty("background")
private BackGround backGround;
#JsonProperty("name")
private String name;
#JsonProperty("gender")
private String gender;
#JsonProperty("dayOfBirth")
private String dayOfBirth;
public static class BackGround {
#JsonProperty("primarySchool")
private String primarySchool;
#JsonProperty("univeristy")
private String univeristy;
}
}

Answer 1

Looking at your JSON objects, there is no way you can figure out what will be there in data parameter. So you can use JsonNode as type for data parameter.
Note: This is the object hierarchy I have created to represent JSON objects
#ToString
class Wrapper {
private Value value;
// getter & setter
}
#ToString
class Value {
private JsonNode data;
private Boolean isGraduated;
// getter & setter
}
#ToString
class Data {
private Info info;
// getter & setter
}
#ToString
class Info {
private Background background;
private String name;
private String gender;
private String dayOfBirth;
// getter & setter
#ToString
static class Background {
private String primarySchool;
private String univeristy;
// getter & setter
}
}
Then you can check the node type before deserialize between List<String> and Info.calss like this,
JsonNodeType type = value.getValue().getData().getNodeType();
You will see type = JsonNodeType.ARRAY if the json object is type 1 and type = JsonNodeType.OBJECT if the json object is type 2.
Check this exaple,
public class Main {
public static void main(String[] args) throws IOException {
// String s = "{\"value\":{\"data\":[\"John\",\"Justin\",\"Tom\"],\"isGraduated\":false}}";
String s = "{\"value\":{\"data\":{\"info\":{\"background\":{\"primarySchool\":\"A school\",\"univeristy\":\"X univeristy\"},\"name\":\"John\",\"gender\":\"male\",\"dayOfBirth\":\"1995-04-24\"}},\"isGraduated\":false}}";
ObjectMapper om = new ObjectMapper();
Wrapper wrapper = om.readValue(s, Wrapper.class);
JsonNodeType type = wrapper.getValue().getData().getNodeType();
if (type == JsonNodeType.ARRAY) {
List<String> data = om.convertValue(wrapper.getValue().getData(), new TypeReference<List<String>>() {});
System.out.println(data);
} else if (type == JsonNodeType.OBJECT) {
Data data = om.convertValue(wrapper.getValue().getData(), Data.class);
System.out.println(data);
}
}
}

Answer 2

Not the general approach but approach for your specific case
ObjectMapper mapper = new ObjectMapper();
ObjectNode root = (ObjectNode) mapper.readTree(jsonContent);
JsonNode data = root.get("value").get("data");
if (data.has("info")) {
Info result = mapper.convertValue(data.get("info"), Info.class);
// handle result as Info instance
} else {
List<String> result = mapper.convertValue(data, new TypeReference<List<String>>() {});
// handle result as list of strings
}