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QUARKUS - MicroProfile REST Client: add a custom, not mapped field

I am following this article https://quarkus.io/guides/rest-client to build a REST Client to parse the output from the restcountries.eu service.
Here the class holding the model:
public class Country {
public String name;
public String alpha2Code;
public String capital;
public List<Currency> currencies;
public static class Currency {
public String code;
public String name;
public String symbol;
}
}
Now, suppose I would like to add a custom fields such as timestamp, to record the instant when this object has been created. I imagine, I would go ahead and add another field like below:
public class Country {
public String name;
public String alpha2Code;
public String capital;
public List<Currency> currencies;
public Instant timestamp; //<--------- added attribute
[....]
My question is: how do I tell the client to populate that field? Normally, I would have done it in the constructor. However, I could not find docs that explain this part.
Thanks for your help
Simone

You can actually do this in the default constructor. Frameworks like JSONB or Jackson expect POJOs to have a default constructor. They will call it when they create an instance of Country.
Use the #JsonbTransient or #JsonIgnore annotations to mark that attribute of your POJO as ignorable in order to avoid the unmarshaller complaining about attributes that cannot be found in the response.
#Data
public class Country {
private String name;
private String alpha2Code;
private String capital;
private List<Currency> currencies;
#JsonbTransient // if you're using JSONB (default in Quarkus)
#JsonIgnore // if you're using Jackson
private Instant timestamp;
public Country() {
this.timestamp = Instant.now();
}
PS The #Data annotation is something you should consider using. Encapsulation is not a bad thing but creating getters/setters is tedious. But Project Lombok certainly helps here.

.net json property conversion in java - #JsonProperty

Need some help here! I have a Java Rest API which is getting data from a .net endpoint and passing it on to the UI. The JSON properties are in capital case and I want to convert them in JAVA before sending it to the UI. Any pointers on this?
In java, I have a class like below:
public class Person {
#JsonProperty("Name")
private String name;
#JsonProperty("Age")
private int age;
}
I am using #JsonProperty as keys in .net are starting with capitalCase. How can I convert this back before sending it to the UI in Java?
Thanks for the help!

Create another class with the same structure and use there other names that you want. Something like this:
// Class to read .NET object
public class Person {
#JsonProperty("Name")
private String name;
#JsonProperty("Age")
private int age;
}
// Class to represent the object in Java REST API
public class Person {
#JsonProperty("name")
private String name;
#JsonProperty("age")
private int age;
}
// Class to represent the object in Java REST API,
// in case you use some standard library that
// uses property names for JSON as is
public class Person {
private String name;
private int age;
}
Of course you should put these classes into different packages.
Your code can look as follows:
xxx.dotnet.Person dotnetPerson = doSomethingViaDotNet(...);
yyy.rest.Person restPerson = new yyy.rest.Person();
restPerson.setName(dotnetPerson.getName());
restPerson.setAge(dotnetPerson.getAge());
...
return restPerson;
If you decide to use MapStruct, your code may looks as follows:
#Mapper
public interface PersonMapper {
PersonMapper INSTANCE = Mappers.getMapper( PersonMapper.class );
yyy.rest.Person dotnetToRest(xxx.dotnet.Person dotnetPerson);
}
Since all attributes have the same names and types you don't need anything else in your mapper.
MapStruct will generate a class that implements this interface. Usage will be as follows:
restPerson = PersonMapper.INSTANCE.dotnetToRest(dotnetPerson);

How to correctly implement properties in complex objects

I have the following models:
class IdNamePair
{
protected int id;
protected String name;
public IdNamePair()
{
id = 0;
name = "";
}
}
class Voyage extends IdNamePair
{
//Several string and int variables
}
class Employee extends IdNamePair
{
//Several string and int variables
}
class Vessel extends IdNamePair
{
//Some string and int variables
}
class Details
{
//Several string and int variables
}
class Summary
{
protected Vessel vessel;
protected Employee chief;
protected Employee operator;
protected List<Details> details
}
class Update
{
protected LocalDateTime created;
protected LocalDateTime modified;
List<Summary> summaries;
//Some string and int variable.
}
I fail to understand how to create a complex Object with several Lists, Maps and instances of other classes. I can replace existing types of fields with corresponding property types (String to StringProperty, double to DoubleProperty, etc.) but how do I handle complex types (List<Summary>, HashMap<String, Vessel>, List<Details>)?
The other question is if I want to support properties, should I convert existing objects or do I need to create new ones. I can replace
class IdNamePair
{
protected int id;
protected String name;
}
with
class IdNamePair
{
protected IntegerProperty id;
protected StringProperty name;
}
or I can provide a new type
class IdNamePairEx
{
protected IntegerProperty id;
protected StringProperty name;
public IdNamePairEx(IdNamePair idNamePair);
///to simple object
public IdNamePair toIdNamePair();
///from simple object
public void fromIdNamePair(IdNamePair idNamePair);
}
and use it when dealing with GUI code. This approach would provide backward compatibility with existing code (JSON serialization, JDBC) but would effectively double the amount of my model classes. What is a preferred way?
Update:
I have a program that communicates to PostgreSQL and executes various CRUD operations. Corresponding classes exist for each table in the database.
I need to develop a new module that would make use of existing classes and I would like to implement GUI updates via bindings and properties.
Do I need to replace each type of variable with it's corresponding property type (String -> StringProperty) or is it better to create similar classes that operate via properties and provide conversion methods (class Vessel -> class VesselWithPropertiesInteadOfRawTypes)?

To define an object in a constructor in Serializable class

I have a JSON response like below image, and I have made a serializable class named as Project
In the image, I have two objects (emergency_contact, and secondary_owner) inside my an array of one object. I'm trying to figure out whether what to do in order to define the object, since I want that details to be present inside my constructor.
I have done this so far:
public class Project implements Serializable {
public int id;
public String name;
public String additional_information;
//Now what to do Emergency contact
public Project(int id, String name, String additional_information){
}
}
I have thought of doing this, public EmergencyContact emergency = new EmergencyContact(param1, param2).
And make a new class named as EmergencyContact, and do a getter and setter for the params. But after doing this, I'm still confused, how would I define it my constructor?
I know I'm close, but I need some help on that.

Sure. You need to have a:
public class EmergencyContact implements Serializable {
public String name;
public String number;
public EmergencyContact(String name, String number){
// assign fields
}
}
and one for the owner:
public class EmergencyOwner implements Serializable {
public String name;
public String number;
public EmergencyOwner(String name, String number){
// assign the fields
}
}
then in your Project class you can add fields of these classes:
public class Project implements Serializable {
public int id;
public String name;
public String additional_information;
public EmergencyContact emergency_contact;
public EmergencyOwner emergency_owner;
public Project(int id, String name, String additional_information, EmergencyContact emergency_contact, EmergencyOwner emergency_owner){
// assign the fields here as well
}
}
that's it. If that's an answer to the question consider to delete this question as it is a duplicated on a 100% :)

As a note, to be correctly from the point of clean code parameters, the fields should be private in a class, and use setters / getters to set/retrieve values from/to those fields.
public class Project implements Serializable {
private int id;
private String name;
private String additional_information;
private EmergencyContact emergency_contact;
private SecondaryOwner secondary_owner;
public Project(int id, String name, String additional_information, EmergencyContact emergencyContact, SecondaryOwner secondaryOwner){
this.id = id;
this.name = name;
this.additional_information = additional_information;
this.emergency_contact = emergencyContact;
this.secondary_owner = secondaryOwner;
}
}
You will define the other two classes the same way. Now, you are probably confused about the constructor of EmergencyContact & SecondaryOwner classes.. You can device both default constructors (without parameters) and a custom one(with parameters to it, just as the one above). If you use the default constructor, make sure to set values to the fields in the object, as following :
EmergencyContact emergencyContact = new EmergencyContact();
emergencyContact.setName("the name");
emergencyContact.setNumber("a number");
then you can use this object in the constructor of Project class
I hope it was clear enough, for any other clarifications feel free to ask.
Happy coding <3

Complex POJO mapping using Dozer

I am new to Dozer, and have done flat mapping from one POJO to another using Dozer xml mapping.But now I want to map complex POJO which is given below and I am stucked how to do it.
// -----------------------Source Classes-----------------------------
public class Source{
public String sourceId;
public Product product;
public List<Item> items;
}
public class Product{
public Integer productId;
public String productName;
}
public class Item{
public Integer id;
public Integer qty;
public String desc;
}
// -----------------------Destination Classes-------------------
public class Destination{
public String destId;
public DestProduct destProduct;
public List<DestItem> destItems;
}
public class DestProduct{
public Integer nProductId;
public String sProductName;
}
public class DestItem{
public Integer nId;
public Integer nQty;
public String sDesc;
}
How do I tell Dozer to map Source to Destination?

You should check Dozer documentation. It has everything you need to map your classes.
I think you are worried mainly for below mappings:
1. Map custom object fields and wrapper classes fields:
Check the Basic property mapping in dozer documentation. Many data type coversions are performed automatically by the Dozer mapping engine. Check the below link for more info.
http://dozer.sourceforge.net/documentation/simpleproperty.html
2. List fields containing custom object mappings:
This is explained at the below link:
http://dozer.sourceforge.net/documentation/collectionandarraymapping.html#
For cases where a feature isn't supported out of the box, you can also write a custom converter:
http://dozer.sourceforge.net/documentation/customconverter.html
Also, It will help to first write simple standalone programs to understand/test a particular mapping before jumping with implementation in your project.