Lab#SE01-2: Maven/Gradle Person and Account stored in JSON

Java SE Lab

javase
lab
composition
factory
JSON
Java SE Lab 01
Author

albertprofe

Published

Tuesday, June 1, 2021

Modified

Friday, November 1, 2024

Create a Maven/Gradle Java SE Project with three classes and Junit to test objects and operations. From here you should add new features: factory pattern, JSON parser and save this JSON on local storage.

💻 Lab#SE01-2: Maven/Gradle Person and Account stored in JSON

Context

This project is the Lab#SE#01-2 (go Lab#SE01-1), you will need to have a basic understanding of the Java programming language, as well as some familiarity with Maven or Gradle for managing dependencies and building the project.

Overall, this project will provide an opportunity for you to learn and apply the basics of Java programming, as well as gain experience with Maven or Gradle, JUnit, user input via the console and data-storage.

By completing this project, you will have a staring foundation in these technologies and be able to build more complex and sophisticated Java applications in the future: singleton, factory, maven, JSON

Goal

The goal of this project is to create three classes in Java (Person, Account and Manager) that implement different algorithms or data structures, and to test them using JUnit.

Now, it this version v2.0 you will storage the data on local JSON and use the factory pattern. For that, your will need to create the Account interface and two subclasses: SavingsAccount and CheckingAccount.

Use de Lombok dependency to write getters and setters.

Tasks

The tasks involved in this project include:

  1. The goal of this project is to create three classes in Java (Person, Account and Manager) that implement different algorithms or data structures, test them using JUnit.
  2. Implementing as well two basic pattern-designs: singleton and factory.
  3. Creating Account interface and two subclasses: SavingsAccount and CheckingAccount.
  4. Writing JUnit tests to verify that the classes work as expected.
  5. Creating a StorageManger class o similar, Utilities package, to storage the data in local JSON.
  6. You should attach the JUnit Test HTML results to documentation.

You should control your versions with GitHub or similar.

Optional

As an optional task, you could also consider allowing the user to input data via the console, rather than using hard-coded test data in your JUnit tests. This would add dynamism and be able to interact with the classes.

Add Credit Card class and create the new feature buy Credit Card in AccountManager.

1 Solving discussion

1.1 Base Classes: factory

Here is an example of how you could create a Lombok Java class for a Person and Account using the factory pattern:

import lombok.AllArgsConstructor;
import lombok.Data;

@Data
@AllArgsConstructor
public class Person {
    private String firstName;
    private String lastName;
}
public interface Account {
    void deposit(double amount);
    void withdraw(double amount);
}

public class SavingsAccount implements Account {
    private double balance;

    public SavingsAccount(double balance) {
        this.balance = balance;
    }

    @Override
    public void deposit(double amount) {
        this.balance += amount;
    }

    @Override
    public void withdraw(double amount) {
        this.balance -= amount;
    }
}
public class CheckingAccount implements Account {
    private double balance;

    public CheckingAccount(double balance) {
        this.balance = balance;
    }

    @Override
    public void deposit(double amount) {
        this.balance += amount;
    }

    @Override
    public void withdraw(double amount) {
        this.balance -= amount;
    }
}
public class AccountManager {
    public static Account createAccount(String accountType, double balance) {
        if (accountType.equalsIgnoreCase("savings")) {
            return new SavingsAccount(balance);
        } else if (accountType.equalsIgnoreCase("checking")) {
            return new CheckingAccount(balance);
        }
        return null;
    }
}

You can then use these classes as follows:

Person john = new Person("John", "Doe");
Account savingsAccount = AccountManager.createAccount("savings", 100.00);
Account checkingAccount = AccountManager.createAccount("checking", 50.00);

The AccountManager class uses the factory pattern to create Account objects based on the specified accountType. This allows you to create different types of accounts without having to specify the exact class to use, and makes it easier to add new types of accounts in the future.

1.2 Base Classes: local storage-JSON

Here is an example of what a Lombok-based Person class and Account class might look like in Java:

import lombok.Data;

@Data
public class Person {
  private String name;
  private int age;
  private String address;
}

@Data
public class Account {
  private int accountNumber;
  private double balance;
  private Person owner;
}

The @Data annotation is a **Lombok* annotation that automatically generates getters and setters for all non-static fields, as well as equals(), hashCode(), and toString() methods. This can help reduce boilerplate code and make your classes more concise and readable.

To save data to a local JSON file, you could use a JSON library like Jackson to convert the objects to JSON strings, and then write those strings to a file. Here is an example of how you might do that:

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class AccountManager {
  private ObjectMapper objectMapper = new ObjectMapper();

  public void saveAccount(Account account) throws JsonProcessingException {
    String json = objectMapper.writeValueAsString(account);
    // write the JSON string to a file
  }
}

How to save an object as a JSON string to a file on your local storage (in this case, c:/data/accounts.json) using Java SE:

import java.io.FileWriter;
import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class AccountManager {
  private ObjectMapper objectMapper = new ObjectMapper();

  public void saveAccount(Account account) throws JsonProcessingException, IOException {
    String json = objectMapper.writeValueAsString(account);

    FileWriter fileWriter = new FileWriter("c:/data/accounts.json");
    fileWriter.write(json);
    fileWriter.close();
  }
}

2 Step-by-step

  1. Create interface Account
  2. Create subclasses SavingsAccount and CheckingAccount
  3. Create AccountManger
  4. Check factory
  5. Parse Account objects to String-JSON
  6. Save String on local .json file
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