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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.

How can i change "Curso" class to print in other class?

I got 2 classes
class Curso{
private String name;
public Curso(String nome){
this.name = nome;
}
public String getName(){
return this.name;
}
}
and
public class testaCurso{
public static void main(String[] args){
Course c1 = new Course("Computer Science");
c1.addDisciplina("AlgProgII");
c1.addDisciplina("SO");
c1.addDisciplina ("Grafos");
System.out.println(c1);
}
}
i gotta modify the Course class so that it can store the names of the Disciplina that make up the course and work for the test above with the output as shown. Consider that a course will not have a maximum of 50 subjects.
output:
Course: Computer Science,
Disciplinas:{ AlgProgII SO Grafos }

class Curso {
private String name;
// Add an list field containg the disciplinas
private final List<String> disciplinas = new ArrayList<>();
public Curso(String name){
this.name = name;
}
public String getName(){
return this.name;
}
// Add a `addDisciplina` method
public void addDisciplina(String name) {
disciplinas.add(name);
}
// Override the `toString` method
#Override
public String toString() {
return "Course: " + name + ", Disciplinas: + ", disciplinas;
}
}

We can implement toString() like the following:
public class Course {
private final String name;
private final List<String> disciplinas;
public Course(String name){
this.name = name;
this.disciplinas = new ArrayList<>();
}
public Course(String name, List<String> disciplinas){
this.name = name;
this.disciplinas = new ArrayList<>(disciplinas);
}
public void addDisciplinas(String discplina){
this.disciplinas.add(discplina);
}
#Override
public String toString() {
return "Course: " + name + ", Disciplinas: {" + disciplinas.stream().collect(Collectors.joining(" ")) +"}";
}
}
Usage:
Course course = new Course("Computer Science", Arrays.asList("AlgProgII", "SO", "Grafos"));
System.out.println(course);
Output:
Course: Computer Science, Disciplinas: {AlgProgII SO Grafos}

Java not showing the output im looking for (Beginner)

Hi guys i am fairly new to Java but ive come across a problem that i cant seem to fix, the problem is in the 'WashingMachine' Class its not displaying the 'spinSpeed' details , any answers will be appreciated
here are my codes:
enter code here
package test;
public class Client {
private String Name;
private String PhoneNo;
Client () {
Name = null;
PhoneNo= null;
}
Client (String N, String P){
Name = N;
PhoneNo = P;
}
public void setName(String N){
Name = N;
}
public void setPhoneNo(String P) {
PhoneNo = P;
}
public String getName(){
return Name;
}
public String setPhoneNo() {
return PhoneNo;
}
public String toString() {
return "\nName: "+ Name + "\nPhoneNo:"+ PhoneNo.toString();
}
}
enter code here
package test;
public class Machine {
private String Make;
private double Price;
private Client Cust;
public Machine(String make, double price, Client cust)
{
Make = make;
Price = price;
Cust = cust;
}
#Override
public String toString() {
return "\n" +"Make of machine: " + Make + "\n" + "Price: " + Price + "\n" + Cust.toString();
}
public String getMake() {
return Make;
}
public double getprice() {
return Price;
}
public Client getcust() {
return Cust;
}
}
enter code here
package test;
public class WashingMachine extends Machine {
private int spinSpeed;
public WashingMachine (String make, double price, Client cust, int spinSpeed){
super(make, price, cust);
}
#Override
public String toString() {
return "WashingMachine [spinSpeed=" + spinSpeed + ", spinSpeed()=" + spinSpeed() + "]";
}
public int spinSpeed() {
return spinSpeed;
}
enter code here
package test;
import java.util.ArrayList;
public class MachinePurchaseTestVerC {
public static void main(String [] args) {
ArrayList<Machine> gadgets = new ArrayList<Machine> ();
Client mCust2 = new Client("Paul", "0487654321");
Client mCust3 = new Client("Chandra", "0487651234");
Client wCust1 = new Client("Catherine", "0412345678");
Client wCust4 = new Client("Mike", "0412348756");
gadgets.add(new WashingMachine("Bosch", 549.50, wCust1, 3500));
gadgets.add(new Machine("Samsung", 678.50, mCust2));
gadgets.add(new Machine("Electrolux", 449.25, mCust3));
gadgets.add(new WashingMachine("LG", 500.00, wCust4, 3200));
for(int i = 0; i<gadgets.size(); i++){
System.out.println(gadgets.get(i).toString());
System.out.println("----------------------------------");
}
}
}

In your WashingMachine class, you forgot to set the speed in your constructor
public WashingMachine (String make, double price, Client cust, int spinSpeed){
super(make, price, cust);
this.spinSpeed = spinSpeed;
}
hope that helps :)

Java Store multiple phone number for one user

Question: Store more than 1 user data with id, name, weight, age, and phone number (can have multiple phone number)
How do I store multiple phone number for one user?
I facing an error "Exception in thread "main" java.lang.NullPointerException at Store_User.main(Store_User.java:29). Anyone can solve it?
import java.util.List;
public class User {
private int usrid;
private String name;
private double weight;
private int age;
private List<String> Pnum;
public User(int usrid, String name, double weight, int age, List<String> Pnum){
this.usrid = usrid;
this.name = name;
this.weight = weight;
this.age = age;
}
public void setUsrid(int usrid) {
this.usrid = usrid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public List<String> getPnum() {
return Pnum;
}
public void setPnum(List<String> pnum) {
Pnum = pnum;
}
int getUID(){
return usrid;
}
}
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
public class Store_User {
public static void main(String[] args) {
User usr1 = new User(1,"Mark", 55.5, 26, Arrays.asList("0140392812", "0123456789"));
User usr2 = new User(2, "Ken", 54.7, 33, Arrays.asList("0129876543"));
User usr3 = new User(3, "Callie", 62.3, 34, Arrays.asList("06123456", "0987654322", "01798654321"));
ArrayList<User> ulist = new ArrayList<User>();
ulist.add(usr1);
ulist.add(usr2);
ulist.add(usr3);
Iterator itr=ulist.iterator();
while(itr.hasNext()){
User usr = (User)itr.next();
System.out.println(usr.getUID() +", " + usr.getName() +", " + usr.getAge() +", " + usr.getWeight());
String out ="";
for(String number: usr.getPnum()){
out += number + ";";
}
System.out.println(out);
}
}
}
Chat conversation end

EDIT: Phone numbers are stored as an ArrayList of Strings and are "linked" to the usrId since they are non-static members of the same class, hence each User object will have it's own id and list of numbers. You can access the phone numbers of a user using:
usr.getPnum()
where usr is an instance of User.java, this will return a ArrayList<String> representing the phone numbers, if you want a specific number you can access the list by index like so:
usr.getPnum().get(0) //The index in this case is 0
User.java
import java.util.List;
public class User {
private int usrid;
private String name;
private double weight;
private int age;
private List<String> Pnum;
public User(int usrid, String name, double weight, int age, List<String> Pnum){
this.usrid = usrid;
this.name = name;
this.weight = weight;
this.age = age;
this.Pnum = Pnum;
}
public void setUsrid(int usrid) {
this.usrid = usrid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public List<String> getPnum() {
return Pnum;
}
public void setPnum(List<String> pnum) {
Pnum = pnum;
}
int getUID(){
return usrid;
}
}
Store_User.java
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
public class Store_User {
public static void main(String[] args) {
User usr1 = new User(1,"Tee Ting Ong", 55.5, 26, Arrays.asList("00000000", "00000000", "00000000"));
User usr2 = new User(2, "Tee Soon Teh", 54.7, 33, Arrays.asList("00000000", "00000000"));
User usr3 = new User(3, "Tee Ting Ken", 62.3, 34, Arrays.asList("00000000"));
ArrayList<User> ulist = new ArrayList<User>();
ulist.add(usr1);
ulist.add(usr2);
ulist.add(usr3);
Iterator itr=ulist.iterator();
while(itr.hasNext()){
User usr = (User)itr.next();
System.out.println(usr.getUID() +", " + usr.getName() +", " + usr.getAge() +", " + usr.getWeight());
//This print out the numbers
String out = "";
for(String number : usr.getPnum()){
out += number + ";";
}
System.out.println(out);
}
}
}

Adding Items to my inventory in Java

I am making a text-based game on JavaFX, and after I hit a tree, I want to get Oak logs.
I have already built my inventory, and I have put default items in it such as Water, Bread, etc.
I am trying to add my Oak Logs to my inventory, but nothing is working.
Here is a part of my code:
Item ItemList[] = {new Bread(), new OakLog()};
Optional<ButtonType> result = alert.showAndWait();
if(result.get() == buttonTypeOak) {
woodcuttingXP = woodcuttingXP + oakXP;
dialogue.appendText("You swing at an Oak tree. + " + oakXP + "XP.\n");
dialogue.appendText("You gathered 1 log.\n");
mainCharacter.getInventory().add(new OakLog());
}
Here is my Item Class:
package game;
public class Item {
private String name;
private int weight;
private int quantity;
private int value;
private String description;
public Item(String name, int value, String description) {
this.name = name;
this.value = value;
this.description = description;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public int getQuantity() {
return quantity;
}
public void setQuantity(int quantity) {
this.quantity = quantity;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String toString() {
return getName();
}
}
And finally, here is my Character class:
package game;
import java.util.ArrayList;
import beverages.Water;
import items.OakLog;
import rawFood.Bread;
public class Character {
private String name;
private int hydrationLevel;
private int healthLevel;
private int hungerLevel;
private int woodcuttingLevel;
public int getWoodcuttingLevel() {
return woodcuttingLevel;
}
public void setWoodcuttingLevel(int woodcuttingLevel) {
this.woodcuttingLevel = woodcuttingLevel;
}
public int getHungerLevel() {
return hungerLevel;
}
public void setHungerLevel(int hungerLevel) {
this.hungerLevel = hungerLevel;
}
private ArrayList<Item> inventory = new ArrayList<Item>();
public ArrayList<Item> getInventory() {
return inventory;
}
public void setInventory(ArrayList<Item> inventory) {
this.inventory = inventory;
}
//creates a person with two basic items
public Character(String name){
this.name = name;
this.hydrationLevel = 100;
this.healthLevel = 100;
this.hungerLevel = 100;
this.woodcuttingLevel = 1;
addToInventory (new Bread());
addToInventory (new OakLog());
addToInventory (new Water());
}
//GETTERS AND SETTERS
public String getName() {
return name;
}
public int getHydrationLevel() {
return hydrationLevel;
}
public void setHydrationLevel(int hydrationLevel) {
this.hydrationLevel = hydrationLevel;
}
public int getHealthLevel() {
return healthLevel;
}
public void setHealthLevel(int healthLevel) {
this.healthLevel = healthLevel;
}
//END GETTERS AND SETTERS
/*Method Name: eat()
*Method Inputs: a piece of food
*Method Purpose: Will allow the user to eat food
*/
public Item getItemFromInventory(int index){
Item item = inventory.get(index);
return item;
}
public void addToInventory(Item item){
if(inventory.contains(item)){
item.setQuantity(item.getQuantity()+1);
}
else{
item.setQuantity(1);
inventory.add(item);
}
}
public String toString(){
return "Character Stats:\nName:" + getName() + "\nHydration: " + getHydrationLevel() + "\nHealth: " + getHealthLevel() + "\nWoodcutting: " + getWoodcuttingLevel();
}
}

In your code, you have:
if(inventory.contains(item)){
item.setQuantity(item.getQuantity()+1);
}
This just updates the quantity of the local variable item in the method, not the item in the inventory.