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how to handle different type of value in single field of JSON payload

I have come across a situation where I have to support existing client, they are using below payload for rest api,
{
"firstName": "First name",
"secondName": "Second name",
"dateOfBirth": "01/12/2020",
"profession": "Software Developer",
"salary": 0,
**"value": "value1"**
}
but now as per requirement, they may send array for value field like below :
{
"firstName": "First name",
"secondName": "Second name",
"dateOfBirth": "01/12/2020",
"profession": "Software Developer",
"salary": 0,
**"value": ["Value1", "value2", "Value3"]**
}
Existing code uses #RequestBody to convert it to PersonDTO person, this class also contains a method called isMutliValue() & getMultiValueFor(), and these methods splits the string based on comma then decide and return values out of it. but now for this requirement, I have to made a modification to check if client is sending array in value or simple string. if it is a simple string then don't split it based on comma and simply process it but if it is an array, bring values out of it and send individual values.
public class PersonDTO {
private String firstName;
private String secondName;
// Formats output date when this DTO is passed through JSON
#JsonFormat(pattern = "dd/MM/yyyy")
// Allows dd/MM/yyyy date to be passed into GET request in JSON
#DateTimeFormat(pattern = "dd/MM/yyyy")
private Date dateOfBirth;
private String profession;
private BigDecimal salary;
private String value;
public PersonDTO(
String firstName, String secondName, Date dateOfBirth, String profession, BigDecimal salary, String value) {
this.firstName = firstName;
this.secondName = secondName;
this.dateOfBirth = dateOfBirth;
this.profession = profession;
this.salary = salary;
this.value = value;
}
public PersonDTO() {}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getSecondName() {
return secondName;
}
public void setSecondName(String secondName) {
this.secondName = secondName;
}
public Date getDateOfBirth() {
return dateOfBirth;
}
public void setDateOfBirth(Date dateOfBirth) {
this.dateOfBirth = dateOfBirth;
}
public String getProfession() {
return profession;
}
public void setProfession(String profession) {
this.profession = profession;
}
public BigDecimal getSalary() {
return salary;
}
public void setSalary(BigDecimal salary) {
this.salary = salary;
}
public Object getValue() {
return value;
}
public void setValue(Object value) {
this.value = value;
}
public boolean isMultiValued() {
return value.split(",").length > 1;
}
public String[] getMultiValues() {
return value.split(",");
}
public String toString(){
return "FirstName : " + firstName +" SecondName : "+ secondName +", Value : "+ value.toString();
}
}
please help me out, how can we handle different type of values in single field of json payload.

In this case you can implement custom deserialization. so for this purpose you should define a PersonDTODeserializer that extends from JsonDeserializer and override deserialize method.
public class PersonDTODeserializer extends JsonDeserializer {
#Override
public Object deserialize(JsonParser jsonParser,
DeserializationContext deserializationContext) throws IOException {
JsonNode node = jsonParser.getCodec().readTree(jsonParser);
String name = node.get("firstName").textValue();
String secondName = node.get("secondName").textValue();
BigDecimal salary = node.get("salary").decimalValue();
String value = "";
JsonNode nodeValue = node.get("value");
if (nodeValue.isArray()) {
Iterator<JsonNode> nodeIterator = nodeValue.iterator();
List<String> values = new ArrayList<>();
while (nodeIterator.hasNext()) {
values.add( nodeIterator.next().textValue());
}
value = String.join(",",values);
} else if (nodeValue.isTextual()) {
value = nodeValue.textValue();
}
return new PersonDTO(name, secondName, salary, value);
}
}
and use it in PersonDTO class.
#JsonDeserialize(using = PersonDTODeserializer.class)
public class PersonDTO {
//other
}

Based on #Hadi J answer,
you can set the deserializer on this field only and not the whole class :
public class PersonDTO {
// ...
#JsonDeserialize(using = ValueDeserializer.class)
private String value;
// ...
}
and the Deserializer:
private static class ValueDeserializer extends JsonDeserializer<String> {
#Override
public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
if( p.isExpectedStartArrayToken() ) {
List<String> values = new ArrayList<String>( p.readValueAs(List.class) );
return String.join(",", values);
} else {
return p.getValueAsString();
}
}
}

How to tolerate a wrong argument type in json with Jackson?

I am integrating with a third party API that responses with an object like this:
{
"name": {
"firstName": "John",
"lastName": "Doe"
}
}
The corresponding Java class looks like this:
class Name {
private String firstName;
private String lastName;
}
Problem: When the name is supposed to be null the API returns an empty string instead of null or an empty object:
{
"name": ""
}
Questing: How to tolerate this behavior on the client side keeping in mind that I call the API using Spring's RestTemplate and Jackson?
In other words, how can I tell Jackson to treat an empty string passed into the name attribute as null, or as an object of the class Name with null properties?
Note: It is not possible to make the API work correctly. I have to handle it on my side.

You either use try / catch and handle the error. Or you write your own Deserializer if you have to handle different scenarios.
Try Catch
Name name;
try {
// Your restTemplate code, will throw Exception when cannot serialize
} catch (Execption e) {
name = null;
}
Deserializer docs:
https://fasterxml.github.io/jackson-databind/javadoc/2.3.0/com/fasterxml/jackson/databind/JsonDeserializer.html
Example on how you can deserialize (not tested)
// On your class specify Deserialzer
#JsonDeserialize(using = YourNameClassDeserializer.class)
public class YourNameClass {
// your class here
}
// Your Deserializer class
public class YourNameClassDeserializer extends StdDeserializer<Item> {
#Override
public Item deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
JsonNode node = jp.getCodec().readTree(jp);
// Use JsonNode to figure out what you are getting and create the object by yourself
return new YourNameClass(firstName, lastName);
}
}
You can one of these solution, both will work for your case.

Jackson has a deserialization feature for this called ACCEPT_EMPTY_STRINGS_AS_NULL_OBJECTS. With Spring boot, you can enable this by enabling the following property within application.properties:
spring.jackson.deserialization.accept-empty-string-as-null-object=true
After that, Jackson will deserialize empty strings as null.
Be aware, since this is a global deserialization feature, this will also happen when the first name would be an empty string.

Try this. This should work. I would say you need to change your java model a bit.
#JsonDeserialize(using = NameDeserializer.class)
public class NameWrapper {
private Name name;
public NameWrapper() {
}
public NameWrapper(Name name) {
this.name = name;
}
public Name getName() {
return name;
}
public void setName(Name name) {
this.name = name;
}
}
Name class will be like
public class Name {
private String firstName;
private String lastName;
public Name() {
}
public Name(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
}
And lastly the deserializer
public class NameDeserializer extends JsonDeserializer {
#Override
public NameWrapper deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException
{
ObjectCodec oc = jsonParser.getCodec();
JsonNode node = oc.readTree(jsonParser);
if(node.get("name").get("firstName") == null && node.get("name").textValue().isEmpty())
return null;
else {
String firstName = node.get("name").get("firstName").textValue();
String lastName = node.get("name").get("lastName").textValue();
return new NameWrapper(new Name(firstName, lastName));
}
}
}
This would work with both these json's
{
"name": {
"firstName": "John",
"lastName": "Doe"
}
}
and
{
"name": ""
}

Create a JSON structure from set of Java Pojo classes

I need to create a JSON object structure from set of java pojo classes. This will provide a better understand of how the objects are structured by just looking at the Json file. I tried both Gson and org.codehaus.jackson.map.ObjectMapper libraries. But couldn't generate all the Json tags relevant to all the fields in java pojo objects. The created json file is only having the values from the values stetted objects. I need to have all the fields of pojo objects in the Json file.
Gson
Hotel hotel = new Hotel(); //This hotel object includes multiple objects and those objects also include multiple objects, lists
Gson gson = new GsonBuilder().create();
String json = gson.toJson(hotel);
System.out.println(json);
ObjectMapper
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(new File("/home/Pojos.json");
This is the class and json response I got.
Hotel.java
package datatypes;
import java.util.ArrayList;
import java.util.List;
public class Hotel {
private String hotelCode;
private String chainCode;
private String hotelName;
private List<Room> rooms = new ArrayList<Room>();
private List<RoomRateRestriction> roomRateRestrictions
= new ArrayList<RoomRateRestriction>();
public String getHotelCode() {
return hotelCode;
}
public void setHotelCode(String hotelCode) {
this.hotelCode = hotelCode;
}
public String getChainCode() {
return chainCode;
}
public void setChainCode(String chainCode) {
this.chainCode = chainCode;
}
public String getHotelName() {
return hotelName;
}
public void setHotelName(String hotelName) {
this.hotelName = hotelName;
}
public List<Room> getRooms() {
return rooms;
}
public void setRooms(List<Room> rooms) {
this.rooms = rooms;
}
public void addRoom(Room room){
this.rooms.add(room);
}
public List<RoomRateRestriction> getRoomRateRestrictions() {
return roomRateRestrictions;
}
public void setRoomRateRestrictions(
List<RoomRateRestriction> roomRateRestrictions) {
this.roomRateRestrictions = roomRateRestrictions;
}
public void addRoomRateRestrictions(
RoomRateRestriction roomRateRestriction) {
this.roomRateRestrictions.add(roomRateRestriction);
}
}
JSON
{
"rooms":[],
"roomRateRestrictions":[]
}

Add serializeNulls() on GsonBuilder() to serialize null fields
Configure Gson to serialize null fields. By default, Gson omits all fields that are null
* during serialization.
class Hotel {
private String name;
private List<Guest> guests = new ArrayList<>(Collections.singleton(new Guest())); //you have to set a value in order to get the structure of the Guest class otherwise it will show an empty list []
//getter setter
}
class Guest {
private String name;
//getter setter
}
Gson
Hotel hotel = new Hotel();
Gson gson = new GsonBuilder().serializeNulls().create();
String json = gson.toJson(hotel);
System.out.println(json);
Output
{
"name":null,
"guests":[
{
"name":null
}
]
}

You can use jackson-databind library.
Maven dependency is :
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.10</version>
</dependency>
Also please find some of sample example below. Here I used Employee Object which is having nested Address object inside it.
Employee.java
public class Employee {
private int empId;
private String firstName;
private String lastName;
private double salary;
private Address address;
public Employee() {}
public Employee(int empId, String firstName, String lastName, double salary) {
this.empId = empId;
this.firstName = firstName;
this.lastName = lastName;
this.salary = salary;
}
public Employee(int empId, String firstName, String lastName, double salary, Address address) {
this.empId = empId;
this.firstName = firstName;
this.lastName = lastName;
this.salary = salary;
this.address = address;
}
public int getEmpId() {
return empId;
}
public void setEmpId(int empId) {
this.empId = empId;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
}
Address.java
public class Address {
private String street;
private String city;
private String state;
private String zip;
private String country;
public Address() {}
public Address(String street, String city, String state, String zip, String country) {
this.street = street;
this.city = city;
this.state = state;
this.zip = zip;
this.country = country;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getZip() {
return zip;
}
public void setZip(String zip) {
this.zip = zip;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
}
I converted a Sample java pojo class to Json and also JSON to pojo object back.
JacksonConvertion.java
public class JacksonConvertion {
public static void main(String[] args) {
pojoToJson();
jsonToPojo();
}
private static void pojoToJson() {
try {
System.out.println("Convert Object to json ");
ObjectMapper mapper = new ObjectMapper();
Address address = new Address("#103, 1st cross, manyta tech park", "Bengaluru", "Karnataka", "560010",
"India");
Address address1 = new Address();
address1.setCity("Bengaluru");
address1.setState("Karnataka");
address1.setCountry("India");
Employee emp = new Employee(1233, "Raju", "BG", 98734.23, address1);
mapper.writeValue(new File("staff.json"), emp);
String jsonString = mapper.writeValueAsString(emp);
System.out.println(jsonString);
} catch (JsonProcessingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private static void jsonToPojo() {
try {
System.out.println("Convert Json to Object ");
ObjectMapper mapper = new ObjectMapper();
Employee employee = mapper.readValue(new File("staff.json"), Employee.class);
System.out.println(employee.getFirstName());
System.out.println(employee.getSalary());
System.out.println(employee.getAddress().getCity());
} catch (IOException e) {
e.printStackTrace();
}
}
}
Also included some of links for your reference.
Link1
Link2

I think this would work fine
Add http://www.java2s.com/Code/Jar/c/Downloadcomfasterxmljacksondatabindjar.htm and http://www.java2s.com/Code/Jar/j/Downloadjacksondatabind205sourcesjar.htm to your library.
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class javaPojo {
public static void main(String args[]){
Hotel hotel = new Hotel();
ObjectMapper mapper = new ObjectMapper();
try {
String json = mapper.writeValueAsString(hotel);
System.out.println("JSON = " + json);
} catch (JsonProcessingException e) {
e.printStackTrace();
}}
}
Hotel
import java.util.ArrayList;
import java.util.List;
public class Hotel {
private String hotelCode;
private String chainCode;
private String hotelName;
private List<Room> rooms = new ArrayList<Room>();
private List<RoomRateRestriction> roomRateRestrictions
= new ArrayList<RoomRateRestriction>();
public String getHotelCode() {
return hotelCode;
}
public void setHotelCode(String hotelCode) {
this.hotelCode = hotelCode;
}
public String getChainCode() {
return chainCode;
}
public void setChainCode(String chainCode) {
this.chainCode = chainCode;
}
public String getHotelName() {
return hotelName;
}
public void setHotelName(String hotelName) {
this.hotelName = hotelName;
}
public List<Room> getRooms() {
return rooms;
}
public void setRooms(List<Room> rooms) {
this.rooms = rooms;
}
public void addRoom(Room room){
this.rooms.add(room);
}
public List<RoomRateRestriction> getRoomRateRestrictions() {
return roomRateRestrictions;
}
public void setRoomRateRestrictions(
List<RoomRateRestriction> roomRateRestrictions) {
this.roomRateRestrictions = roomRateRestrictions;
}
public void addRoomRateRestrictions(
RoomRateRestriction roomRateRestriction) {
this.roomRateRestrictions.add(roomRateRestriction);
}
}
Room
public class Room {
}
RoomRateRestriction
public class RoomRateRestriction {
}
OUTPUT - JSON = {"hotelCode":null,"chainCode":null,"hotelName":null,"rooms":[],"roomRateRestrictions":[]}

how to get Json objects from json array and use them with model class

I want to link my received json data to my pojo class using gson library.I used volley library to receive the data.What should i do so that whenever i call getter methods from my pojo class then i get the received json data.
My Json data is in this format.
{
"vichList":[ {
id=1,
username="abc....},
{....},
]
}
I want to get this json data into my pojo class.
Vich.java
public class GetfeedResponse {
private List<Vich> vichList;
public List<Vich> getVichList() {
return vichList;
}
public void setVichList(List<Vich> vichList) {
this.vichList = vichList;
}
}
Vich.java
public class Vich {
private int id;
private String username;
private String full_name;
private String createdAt;
private int vich_id;
private String vich_content;
private String city;
private int like_count;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getFull_name() {
return full_name;
}
public void setFull_name(String full_name) {
this.full_name = full_name;
}
public String getCreatedAt() {
return createdAt;
}
public void setCreatedAt(String createdAt) {
this.createdAt = createdAt;
}
public int getVich_id() {
return vich_id;
}
public void setVich_id(int vich_id) {
this.vich_id = vich_id;
}
public String getVich_content() {
return vich_content;
}
public void setVich_content(String vich_content) {
this.vich_content = vich_content;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public int getLike_count() {
return like_count;
}
public void setLike_count(int like_count) {
this.like_count = like_count;
}
}
Here i am getting the json response using volley library.
httpUtil.getrequest(url,this,new VolleyCallback(){
#Override
public void onSuccess(String result){
GetfeedResponse getfeedResponse = new GetfeedResponse();
// for(Vich vich : getfeedResponse.getVichList()){
// }
Log.d("Response Result:",result);
}
How can i get objects from json array and use them with the help of pojo class?

Using Gson
Add the following dependency in your gradle:
implementation 'com.google.code.gson:gson:2.8.5'
In your onSuccess()
GetfeedResponse getfeedResponse=new Gson().fromJson(result, GetfeedResponse.class);
If you wish to use Volley and POJO its better to use custom GSON request. Check this link : Custom GSON request With Volley

GSON:
GetfeedResponse parsed = new Gson().fromJson(response, GetfeedResponse.class);
Jackson:
GetfeedResponse parsed = new ObjectMapper().readValue(response, GetfeedResponse.class);
Additionally, if you wanted to convert only list of Vich items (and you stripped your JSON accordingly) you could do following:
[ {
id=1,
username="abc....},
{....},
]
List<Vich> viches = Arrays.asList(new Gson().fromJson(vichItemsJson, Vich[].class));

Trouble converting Json Array into Pojo with array of pojos

JSON String
{
"order":{
"address":{
"city":"seattle"
},
"orderItem":[
{
"itemId":"lkasj",
"count":2
},
{
"itemId":"ldka",
"count":3
}
]
}
}
Order Class
public class Order {
private OrderItem[] orderItems;
private CustomerAddress address;
Order(OrderItem[] orderItems, CustomerAddress address ) {
this.orderItems = orderItems;
this.address = address;
}
public OrderItem[] getOrderItems() {
return orderItems;
}
public void setOrderItems(OrderItem[] orderItems) {
this.orderItems = orderItems;
}
public CustomerAddress getAddress() {
return address;
}
public void setAddress(CustomerAddress address) {
this.address = address;
}
}
My OrderItem class
package com.cbd.backend.model;
import org.springframework.data.annotation.Id;
public class OrderItem {
#Id
private String id;
private String itemId;
private String count;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
unit Test that blows up
public String getItemId() {
return itemId;
}
public void setItemId(String itemId) {
this.itemId = itemId;
}
public String getCount() {
return count;
}
public void setCount(String count) {
this.count = count;
}
}
Unit test to demonstrate issue
package com.cbd.backend.model;
import com.google.gson.Gson;
import org.junit.Test;
import static org.junit.Assert.*;
public class OrderTest {
Gson gson = new Gson();
#Test
public void gsonToOrder() {
Order order = gson.fromJson( a, Order.class );
assertNotNull(order);
assertNotNull(order.getOrderItems()[0]);
}
private final String a = "{ \"order\": { \"address\": { \"city\": \"seattle\" },\"orderItem\":[{ \"itemId\":\"lkasj\", \"count\":2 }, { \"itemId\":\"ldka\", \"count\":3 } ] } }";
}
Should I be using something other than gson or am i constructing this incorrectly

There are two problems in your code:
The root element of your JSON is "order", but the class does not have a property with this name. Try changing you model or just removing the element from the JSON.
There is a mismatch in the name of the "orderItem" property. It is plural in the class, but singular in the JSON.
To sum it up, the following JSON will work without any changes to the code.
{
"address":{
"city":"seattle"
},
"orderItems":[
{
"itemId":"lkasj",
"count":2
},
{
"itemId":"ldka",
"count":3
}
]
}
Also, "count" as it appears in the JSON seems to be numeric, so you might want to change the type of OrderItem.count to int or java.lang.Integer.