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How do I leverage a json mapping file to convert from one pojo to another pojo?

I have two POJOs (Person.java and User.java) that contain similar information. See below:
public class Person {
private String first_name;
private String last_name;
private Integer age;
private Integer weight;
private Integer height;
public String getFirst_name() {
return first_name;
}
public void setFirst_name(String first_name) {
this.first_name = first_name;
}
public String getLast_name() {
return last_name;
}
public void setLast_name(String last_name) {
this.last_name = last_name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Integer getWeight() {
return weight;
}
public void setWeight(Integer weight) {
this.weight = weight;
}
public Integer getHeight() {
return height;
}
public void setHeight(Integer height) {
this.height = height;
}
}
public class User {
private String name_first;
private String name_last;
private Integer my_age;
private Integer my_weight;
private String social_security;
public String getName_first() {
return name_first;
}
public void setName_first(String name_first) {
this.name_first = name_first;
}
public String getName_last() {
return name_last;
}
public void setName_last(String name_last) {
this.name_last = name_last;
}
public Integer getMy_age() {
return my_age;
}
public void setMy_age(Integer my_age) {
this.my_age = my_age;
}
public Integer getMy_weight() {
return my_weight;
}
public void setMy_weight(Integer my_weight) {
this.my_weight = my_weight;
}
public String getSocial_security() {
return social_security;
}
public void setSocial_security(String social_security) {
this.social_security = social_security;
}
}
I have defined a mapping.json file as shown below using GSON.
{
"columnMap": [
{
"userColumn": "name_first",
"personColumn": "first_name"
},
{
"userColumn": "last_first",
"personColumn": "first_last"
},
{
"userColumn": "my_age",
"personColumn": "age"
},
{
"userColumn": "my_weight",
"personColumn": "weight"
}
]
}
public class Mapping {
private ArrayList<Pair> columnMap;
public Mapping(){
columnMap = new ArrayList<>();
}
public ArrayList<Pair> getColumnMap() {
return columnMap;
}
public void setColumnMap(ArrayList<Pair> columnMap) {
this.columnMap = columnMap;
}
}
I am writing a utility class helper function that converts between a Person and User object the mapped pairs.
public class Pair {
private String userColumn;
private String personColumn;
public String getUserColumn() {
return userColumn;
}
public void setUserColumn(String userColumn) {
this.userColumn = userColumn;
}
public String getPersonColumn() {
return personColumn;
}
public void setPersonColumn(String personColumn) {
this.personColumn = personColumn;
}
public static void main(String args[]){
}
}
My question is below:
As you can see the returnVal object is being set by me (the programmer) to convert from a User POJO to a Person POJO. How do I leverage the pre-defined mapping.json to do this? The reason I am asking is in the future, the mapping.json file may change (maybe the weight mapping no longer exists). So I am trying to avoid re-programming this Utility.userToPerson() function. How can I achieve this? I am thinking Java reflection is the way to go, but I would like to hear back from the Java community.
public class Utility {
public static Person userToPerson(User u){
Person returnVal = new Person();
returnVal.setAge(u.getMy_age()); // <-- Question How do I leverage mapping.json here?
returnVal.setFirst_name(u.getName_first());
returnVal.setLast_name(u.getName_last());
returnVal.setWeight(u.getMy_weight());
return returnVal;
}
}

You can introspect the beans (i.e. User and Person) for the field names and call corresponding getter from User to fetch the value. Later call corresponding setter in Person.
Here I have taken userToPersonFieldsMap for mapping the field, you can load mapping from JSON file and construct the map accordingly.
Important code section is the for loop, where it dynamically calls getter and setter and does the job.
import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
public class UserToPersonMapper {
public static void main(String[] args) throws IntrospectionException, InvocationTargetException, IllegalAccessException {
Map<String, String> userToPersonFieldsMap = new HashMap<>();
userToPersonFieldsMap.put("name_first", "first_name");
userToPersonFieldsMap.put("last_first", "first_last");
userToPersonFieldsMap.put("age", "personAge");
//existing user
User user = new User("Tony", "Stark", 20);
//new person - to be initialised with values from user
Person person = new Person();
for (Map.Entry<String, String> entry : userToPersonFieldsMap.entrySet()) {
Object userVal = new PropertyDescriptor(entry.getKey(), User.class).getReadMethod().invoke(user);
new PropertyDescriptor(entry.getValue(), Person.class).getWriteMethod().invoke(person, userVal);
}
System.out.println(user);
System.out.println(person);
}
}
class User {
private String name_first;
private String last_first;
private int age;
public User(String name_first, String last_first, int age) {
this.name_first = name_first;
this.last_first = last_first;
this.age = age;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName_first() {
return name_first;
}
public String getLast_first() {
return last_first;
}
public void setName_first(String name_first) {
this.name_first = name_first;
}
public void setLast_first(String last_first) {
this.last_first = last_first;
}
#Override
public String toString() {
return "User{" +
"name_first='" + name_first + '\'' +
", last_first='" + last_first + '\'' +
", age=" + age +
'}';
}
}
class Person {
private String first_name;
private String first_last;
private int personAge;
public void setFirst_name(String first_name) {
this.first_name = first_name;
}
public void setFirst_last(String first_last) {
this.first_last = first_last;
}
public String getFirst_name() {
return first_name;
}
public String getFirst_last() {
return first_last;
}
public int getPersonAge() {
return personAge;
}
public void setPersonAge(int personAge) {
this.personAge = personAge;
}
#Override
public String toString() {
return "Person{" +
"first_name='" + first_name + '\'' +
", first_last='" + first_last + '\'' +
", personAge=" + personAge +
'}';
}
}
You can tweak and try it out this example to make it more align with your requirement.
Note:
This solution uses reflection.

Age filter in Java with ArrayList

I want to make a method that tells me who is the oldest person in the ArrayList and who is the youngest person. The method will receive the arraylist that i want to apply the method, i have 3 in my code, each one is an contact list.
The method is suppose to return the name of the person, but i don't know how to do it. Familia, Profissional and Amigos are my arraylists and "idade" = age and "nome" = name.
package com.company;
public class Contato {
public String nome;
public int idade;
public String sexo;
public String profissao;
public String telefone;
public String email;
public Contato(String nome, int idade, String sexo, String profissao, String telefone, String email) {
this.nome = nome;
this.idade = idade;
this.sexo = sexo;
this.profissao = profissao;
this.telefone = telefone;
this.email = email;
}
#Override
public String toString() {
return "" +
nome + ',' +
idade + " anos de idade, " +
"do sexo " + sexo + ',' +
profissao + ',' +
" telefone nº " + telefone + ", " +
"e-mail:" + email;
}
public String getNome() {
return nome;
}
public void setNome(String nome) {
this.nome = nome;
}
public int getIdade() {
return idade;
}
public void setIdade(int idade) {
this.idade = idade;
}
public String getSexo() {
return sexo;
}
public void setSexo(String sexo) {
this.sexo = sexo;
}
public String getProfissao() {
return profissao;
}
public void setProfissao(String profissao) {
this.profissao = profissao;
}
public String getTelefone() {
return telefone;
}
public void setTelefone(String telefone) {
this.telefone = telefone;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
package com.company;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
public class GestaoContatos extends Contato {
ArrayList<Contato> Familia = new ArrayList();
ArrayList<Contato> Amigos = new ArrayList();
ArrayList<Contato> Profissional = new ArrayList();
public GestaoContatos(Contato c) {
super(c.nome, c.idade, c.sexo, c.profissao, c.telefone, c.email);
}
public void adicionaContato(String nomeAgenda, Contato contato) {
if( nomeAgenda == "Familia"){
Familia.add(contato);
} else
if(nomeAgenda == "Amigos"){
Amigos.add(contato);
} else
if(nomeAgenda == "Profissional") {
Profissional.add(contato);
} else
System.out.println("Indispnível");
}
public void eliminaContato(String nomeContato) {
for(int i = 0; i < Familia.size(); i++) {
if(getFamilia().contains(nomeContato)) {
Familia.remove(nomeContato);
}
}
}
public void printaLista(String nomeAgenda){
if(nomeAgenda.equals("Familia")) {
Familia.forEach(System.out::println);
}
if(nomeAgenda.equals("Amigos")) {
Amigos.forEach(System.out::println);
}
if(nomeAgenda.equals("Profissional")) {
Profissional.forEach(System.out::println);
}
else {
throw new RuntimeException("Opcao invalida");
}
}
public void tooString() {
var contatos = new ArrayList<Contato>();
Familia.forEach(it -> contatos.add(it));
Amigos.forEach(it -> contatos.add(it));
Profissional.forEach(it -> contatos.add(it));
System.out.println(contatos.toString());
}
public void olderPerson(String nomeAgenda){
int i = 0;
if (nomeAgenda.equals("Amigos")) {
for (i = 0; Familia.size(); i++) {
Familia.stream().filter();
}
}
}
public void geraListaBinaria() throws IOException {
var file = new File("C:\\Users\\Jorge Luiz\\Desktop\\contatos.txt");
var writer = new FileWriter(file.getName());
writer.write(this.getProfissional().toString());
writer.write(this.getFamilia().toString());
writer.write(this.getProfissional().toString());
writer.close();
}
public ArrayList<Contato> getFamilia() {
return Familia;
}
public void setFamilia(ArrayList<Contato> familia) {
Familia = familia;
}
public ArrayList<Contato> getAmigos() {
return Amigos;
}
public void setAmigos(ArrayList<Contato> amigos) {
Amigos = amigos;
}
public ArrayList<Contato> getProfissional() {
return Profissional;
}
public void setProfissional(ArrayList<Contato> profissional) {
Profissional = profissional;
}
}

If you want to return oldest person in one list:
public Contato oldestPerson(String nomeAgenda){
return Familia.stream()
.filter(c -> c.getNome().equals(nomeAgenda)) // contatos named nomeAgenda
.max(Comparator.comparingInt(Contato::getIdade)) // take oldest
.get();
}
For all lists you can do:
public Contato oldestPerson(){
return Stream.of(Familia, Amigos, Profissional)
.flatMap(Collection::stream) // flatting to one long stream
.filter(c -> c.getNome().equals(nomeAgenda)) // contatos named nomeAgenda
.max(Comparator.comparingInt(Contato::getIdade))
.get();
}
EDIT
Based on the comment, we should change a couple of things to achieve what you want. First, we should define a Map<String, List<Contato>> and populate it in the constructor:
private Map<String, List<Contato>> contatoGroups;
private static final String familiaKey = "Familia";
private static final String amogisKey = "Amigos";
private static final String profissionalKey = "Profissional";
public GestaoContatos(Contato c) {
super(c.nome, c.idade, c.sexo, c.profissao, c.telefone, c.email);
contatoGroups.put(familiaKey, new ArrayList<>());
contatoGroups.put(amogisKey, new ArrayList<>());
contatoGroups.put(profissionalKey, new ArrayList<>());
}
(Consider using enum instead of String as key in the map)
Then wherever you want to get a group, for example: Familia, you should do:
List<Contato> contatoes = contatoGroups.get(familiaKey);
And then we should change the oldestPerson() like this:
public Contato oldestPerson(String nomeAgenda){ // nomeAgenda could be "Familia", "Amigos"...
List<Contato> selectedGroup = contatoGroups.get(nomeAgenda);
return selectedGroup.stream()
.max(Comparator.comparingInt(Contato::getIdade)) // take oldest
.get();
}

Using Bytebuddy to intercept setter

lets asume i have a Interface like that:
public interface User extends Element {
String getName();
String getPassword();
}
and a implementing class like that:
public class BaseUser implements User {
#Override
public String getId() {
return id;
}
#Override
public String getName() {
return name;
}
#Override
public String getPassword() {
return password;
}
public void setId(String id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
System.out.println("Set name to " + name);
}
public void setPassword(String password) {
this.password = password;
}
private String id;
private String name;
private String password;
}
Now i want to use bytebuddy to create a interceptor/proxy which catches the call onto the setter, store the changed value and call the real method also.
At the end i want to "ask" the interceptor/proxy for the called setter and the changed values.
I tried a lot considering also the tutorials but up to now i found no working solution. Maybe someone could help me pls.
And here is the Interceptor:
public class GenericInterceptor implements InvocationHandler {
#Override
#RuntimeType
public Object invoke(#This Object proxy, #Origin Method method, #AllArguments Object[] args) throws Throwable {
if (isSetter(method, args)) {
intercept(proxy, method, args);
}
return method.invoke(proxy, args);
}
}
Here is my current 'test' code:
public static void main(String[] args) {
final ByteBuddy bb = new ByteBuddy();
final GenericInterceptor interceptor = new GenericInterceptor();
bb.subclass(BaseUser.class)
.method(isDeclaredBy(BaseUser.class).and(isSetter()))
.intercept(MethodDelegation.to(interceptor))
.make()
.load(BaseUser.class.getClassLoader(), ClassLoadingStrategy.Default.WRAPPER);
final BaseUser user = new BaseUser();
user.setName("my name");
}
EDIT:
public interface Element {
String getId();
}
public class GenericInterceptor<T extends Element> {
public GenericInterceptor(Class<T> type) {
this.type = type;
}
public Map<String, Object> getChanges(T obj) {
final String id = obj.getId();
return changes.get(id);
}
#RuntimeType
public void invoke(#This T proxy, #Origin Method method, #AllArguments Object[] args) throws Throwable {
System.out.println("invoke " + method.getName() + " " + Arrays.toString(args));
intercept(proxy, method, args);
}
private Object getCurrentValue(T proxy, final Field field) {
try {
return field.get(proxy);
} catch (IllegalArgumentException | IllegalAccessException e) {
return null;
}
}
private Field getSetterField(Method setter) {
final String setterName = setter.getName();
Field f = assignedFields.get(setterName);
if (f != null) return f;
final String fieldName = Character.toLowerCase(setterName.charAt(3)) + setterName.substring(4);
try {
f = type.getDeclaredField(fieldName);
if (f == null) return null;
f.setAccessible(true);
assignedFields.put(setterName, f);
return f;
} catch (NoSuchFieldException | SecurityException e) {
return null;
}
}
private void intercept(T proxy, Method setter, Object[] args) {
final Field field = getSetterField(setter);
if (field == null)
return;
final Object currentValue = getCurrentValue(proxy, field);
final Object newValue = args[0];
System.out.println("Set from " + currentValue + " to " + newValue);
final String id = proxy.getId();
Map<String, Object> changeMap = changes.get(id);
if (changeMap == null) {
changeMap = new HashMap<>();
}
changeMap.put(field.getName(), currentValue);
changes.put(id, changeMap);
}
private final Map<String, Field> assignedFields = new HashMap<>();
private final Map<String, Map<String, Object>> changes = new LinkedHashMap<>();
private final Class<T> type;
}

You can call orignal method using MethodDelegation.to(...).andThen(SuperMethodCall.INSTANCE).
public class ByteBuddyTest {
public static void main(String[] args) throws IllegalAccessException, InvocationTargetException, InstantiationException {
GenericInterceptor interceptor = new GenericInterceptor ();
Class<?> clazz = new ByteBuddy()
.subclass(BaseUser.class)
.method(ElementMatchers.isDeclaredBy(BaseUser.class).and(ElementMatchers.isSetter()))
.intercept(SuperMethodCall.INSTANCE.andThen(MethodDelegation.to(interceptor))))
.make()
.load(ByteBuddyTest.class.getClassLoader())
.getLoaded();
BaseUser user1 = (BaseUser) clazz.getConstructors()[0].newInstance();
BaseUser user2 = (BaseUser) clazz.getConstructors()[0].newInstance();
user1.setName("user1");
user1.setPassword("password1");
user2.setName("user2");
user2.setPassword("password2");
System.out.println(interceptor.getInterceptedValue("user1", "name"));
System.out.println(interceptor.getInterceptedValue("user1", "password"));
System.out.println(interceptor.getInterceptedValue("user2", "name"));
System.out.println(interceptor.getInterceptedValue("user2", "password"));
user1.setPassword("password2");
user1.setPassword("password3");
}
public static class GenericInterceptor {
private Map<String, Object> interceptedValuesMap = new HashMap();
public void set(String obj, #This User user, #Origin Method setter) {
// assume that user name is unique so we can use it as a key in values map.
// or define equals/hashcode in GenericUser object and use it as a key directly
String setterName = setter.getName();
String propertyName = setterName.substring(3, setterName.length()).toLowerCase();
String key = user.getName() + "_" + propertyName;
System.out.println("Setting " + propertyName + " to " + obj);
System.out.println("Previous value " + interceptedValuesMap.get(key));
interceptedValuesMap.put(key, obj);
}
public Object getInterceptedValue(String userName, String fieldName) {
return interceptedValuesMap.get(userName + "_" + fieldName);
}
}
public static interface User {
String getName();
String getPassword();
}
public static class BaseUser implements User {
#Override
public String getName() {
return name;
}
#Override
public String getPassword() {
return password;
}
public void setName(String name) {
this.name = name;
}
public void setPassword(String password) {
this.password = password;
}
private String name;
private String password;
}
}

Created add() method to insert objects into an array and all i get are null values

this is a class called Doglist to add the object to an array.
public class DogList {
private int numItems;
private DogItem[] dogListArray;
private int position;
DogList () {
numItems=0;
position = 0;
dogListArray = new DogItem[10];
}
public void add (DogItem item) {
dogListArray[numItems++]= new DogItem(item.getName(),
item.getBreed(),
item.getWeight(),
item.getOwner1(),
item.getOwner2()
);
}
public String toString() {
String result = "";
for (int i=0; i<numItems; i++) {
result += dogListArray[i].toString() + "\n";
}
return result;
}
public DogItem searchForDogItem (DogItem gi) {
System.out.println("Here is your obj value: " + gi );
return null;
}//This is the one im having trouble with.
}
I have all the setters and getters in the DogItem class.
and this is from the UI where i get the dog info(name, breed, weight, owners1&2 names)
public void searchForItem (String name ) {
DogItem gi = new DogItem (name);
gi = gl.searchForDogItem(gi);
if (gi==null) {
msgTextField.setText("Dog Not Found");
} else {
nameTextField.setText(String.valueOf(gi.getName()));
breedTextField.setText(String.valueOf(gi.getBreed()));
weightTextField.setText(String.valueOf(gi.getWeight()));
owner1TextField.setText(String.valueOf(gi.getOwner1()));
owner2TextField.setText(String.valueOf(gi.getOwner2()));
}
}
Ill try and clear things up as i go.
this is the output i get
Here is your obj value: null null 0.0 null null

Ok so here is what it probably should look like instead. Just from what I saw wrong already. However you'd probably want to override the toString() method of DogItem.
Main method example of this:
public class Main {
public static void main(String[] args) {
DogItem dogItem = new DogItem("Spot", "Dalmation", "45", "Bob", "Sandy");
DogItem.add(dogItem);
DogItem result = DogItem.searchForItem("Spot");
if (result == null) {
System.out.println("Dog not found");
// GUI error output goes here
} else {
System.out.println("Here is your obj value: " + result);
// Where your GUI stuff goes
}
}
}
DogItem example of this:
public class DogItem {
private static DogItem[] dogListArray = new DogItem[100];
private static int numItems = 0;
private String name;
private String breed;
private String weight;
private String owner1;
private String owner2;
public DogItem(String name, String breed, String weight, String owner1, String owner2) {
this.name = name;
this.breed = breed;
this.weight = weight;
this.owner1 = owner1;
this.owner2 = owner2;
}
public static void add(DogItem dogItem) {
dogListArray[numItems++] = dogItem;
}
public static DogItem searchForItem(String name) {
DogItem dogItem = null;
for (DogItem result : dogListArray) {
if (result != null) {
if (result.getName() == name) {
dogItem = result;
}
}
}
return dogItem;
}
#Override
public String toString() {
String result = name + ", " + breed + ", " + weight + ", " + owner1 + " " + owner2;
return result;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getBreed() {
return breed;
}
public void setBreed(String breed) {
this.breed = breed;
}
public String getWeight() {
return weight;
}
public void setWeight(String weight) {
this.weight = weight;
}
public String getOwner1() {
return owner1;
}
public void setOwner1(String owner1) {
this.owner1 = owner1;
}
public String getOwner2() {
return owner2;
}
public void setOwner2(String owner2) {
this.owner2 = owner2;
}
}
These would be recommended changes from me though:
private static ArrayList<String> owners;
private static ArrayList<DogItem> dogsList;
public DogItem(String name, String breed, String weight, String owner) {
this.name = name;
this.breed = breed;
this.weight = weight;
this.owners.add(owner);
}
public void init() {
owners = new ArrayList<String>();
dogsList = new ArrayList<DogItem>();
}
public void addDog(DogItem dogItem) {
dogsList.add(dogItem);
}
public DogItem searchForItem(String name) {
DogItem dogItem = null;
for (DogItem result : dogsList) {
if (result != null) {
if (result.getName() == name) {
dogItem = result;
}
}
}
return dogItem;
}
public void addOwner(String owner) {
owners.add(owner);
}
public String getOwner() {
return owners.get(owners.size() - 1);
}

how to populate jcombobox with arrays that match specific criteria

When i try my code below the list isn't be populated with the specific arrays please help i'm pretty new to coding GUI in netbeans
private void bookingListJCBActionPerformed(java.awt.event.ActionEvent evt) {
for(int i = 0;i<dataSource.getBookingList().size();i++){
Bookings tempBooking = dataSource.getBookingList().get(i);
boolean tempFinish = tempBooking.getFinish();
String tempMechanic = tempBooking.getMechanic();
String tempClerk = tempBooking.getClerk();
String tempService = tempBooking.getService();
if(tempFinish == true){
bookingListJCB.addItem(tempBooking);
mechanicJTF.setText(tempMechanic);
seriveceClerkJTF.setText(tempMechanic);
serviceJTF.setText(""+tempService );
finishJTF.setText(""+tempFinish);
}
}
// TODO add your handling code here:
}
Here is the Bookings class how i don't know why the combo box isn't displaying anything
public class Bookings {
private String vehicle;
private String clerk;
private String service;
private String mechanic;
private boolean finish;
public Bookings() {
}
public Bookings(String vehicle, String clerk, String service, String mechanic, boolean finish) {
this.vehicle = vehicle;
this.clerk = clerk;
this.service = service;
this.mechanic = mechanic;
this.finish = finish;
}
public String getVehicle() {
return vehicle;
}
public void setVehicle(String vehicle) {
this.vehicle = vehicle;
}
public String getClerk() {
return clerk;
}
public void setClerk(String clerk) {
this.clerk = clerk;
}
public String getService() {
return service;
}
public void setService(String service) {
this.service = service;
}
public String getMechanic() {
return mechanic;
}
public void setMechanic(String mechanic) {
this.mechanic = mechanic;
}
public boolean getFinish() {
return finish;
}
public void setFinish(boolean finish) {
this.finish = finish;
}
#Override
public String toString() {
return "Bookings{" + "vehicle=" + vehicle + ", clerk=" + clerk + ", service=" + service + ", mechanic=" + mechanic + ", finish=" + finish + '}';
}
}