JSON Lab

Learning Goals

Work with JSON files in Java.

Instructions

Reusing the CustomerDriver and FavoriteCustomer classes from the CSV lab, modify the code to read and write JSON formatted files instead of CSV formatted files. The JSON file format would look like this:

[
  {
    "firstName": "Leslie",
    "lastName": "Knope",
    "mealChoice": "waffles with whipped cream"
  }
]

To implement the reading and writing of a JSON file, consider the following instructions and tips:

Add the Jackson library to the module.
Write the method to write to a JSON file.
- Use the ObjectMapper class to write to a JSON file.
  - Refer back to the JSON lesson.
Write the method to read from a JSON file.
- Either add a default constructor to the FavoriteCustomer class or add Jackson annotations to an existing constructor.
- Use the ObjectMapper class to read from a JSON file.
  - Refer back to the JSON lesson.
  - Read in an array of FavoriteCustomer objects.
- Return a String to print out to the console the FavoriteCustomer objects that were read in from the JSON.
  - The output should look like:
    - Leslie Knope always orders the waffles with whipped cream
Remove the @Disabled annotation from the unit tests and ensure that the tests pass successfully still. Refactor as necessary. 12345678910111213141516171819202122232425262728293031323334353637383940404143454

Starter Code

Consider the following starter code:

public class FavoriteCustomer {
    private String firstName;
    private String lastName;
    private String mealChoice;

    public FavoriteCustomer(String firstName, String lastName, String mealChoice) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.mealChoice = mealChoice;
    }

    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 String getMealChoice() {
        return mealChoice;
    }

    public void setMealChoice(String mealChoice) {
        this.mealChoice = mealChoice;
    }

    @Override
    public String toString() {
        return String.format("%s %s always orders the %s",
                firstName,
                lastName,
                mealChoice);
    }
}

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class CustomerDriver {

    public static void main(String[] args) {
        List<FavoriteCustomer> customers = new ArrayList<FavoriteCustomer>();
        Scanner scanner = new Scanner(System.in);
        String input = "";
        do {
            System.out.println("What is the first name of the favorite customer?");
            String firstName = scanner.nextLine();
            System.out.println("What is the last name of the favorite customer?");
            String lastName = scanner.nextLine();
            System.out.println("What is the meal choice of the favorite customer?");
            String mealChoice = scanner.nextLine();
            customers.add(new FavoriteCustomer(firstName, lastName, mealChoice));
            System.out.println("Add another customer? (type \"no\" to exit)");
            input = scanner.nextLine();
            System.out.println();
        } while(!input.equalsIgnoreCase("no"));

        writeFile("customer.json", customers);
        System.out.println(readFile("customer.json"));
    }

    public static String readFile(String filepath) {
        // Write your code here!
    }

    public static void writeFile(String filepath, List<FavoriteCustomer> customers) {
        // Write your code here!
    }
}

Unit Tests

Consider the following unit tests to help you implement the writeFile() and readFile() methods:

import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

import static org.junit.jupiter.api.Assertions.*;

class CustomerDriverTest {

    FavoriteCustomer ron;
    FavoriteCustomer leslie;
    FavoriteCustomer ben;
    List<FavoriteCustomer> customers;

    @BeforeEach
    void setUp() {
        ron = new FavoriteCustomer(
                "Ron",
                "Swanson",
                "four-horse meals of the egg-pork-alypse"
        );
        leslie = new FavoriteCustomer(
                "Leslie",
                "Knope",
                "waffles with whipped cream"
        );
        ben = new FavoriteCustomer(
                "Ben",
                "Wyatt",
                "calzone"
        );

        customers = new ArrayList<FavoriteCustomer>();
    }

    @AfterEach
    void tearDown() {
    }

    @Disabled
    @Test
    void testReadOneCustomer() {
        String filename = "test-customer1.json";
        assertEquals(ron.toString(), CustomerDriver.readFile(filename));
    }

    @Disabled
    @Test
    void testReadMultipleCustomers() {
        String filename = "test-customer2.json";
        String expectedOutput = String.format("%s%n%s%n%s", ron.toString(), leslie.toString(), ben.toString());
        assertEquals(expectedOutput, CustomerDriver.readFile(filename));
    }

    @Disabled
    @Test
    void testReadNoCustomers() {
        String filename = "test-customer3.json";
        CustomerDriver.writeFile(filename, customers);
        assertEquals("", CustomerDriver.readFile(filename));
    }

    @Disabled
    @Test
    void testWriteOneCustomer() {
        Path path = Paths.get("test-customer4.json");
        customers.add(ben);
        CustomerDriver.writeFile(path.toString(), customers);
        String expectedOutput = "[ {\n" +
                "  \"firstName\" : \"Ben\"," +
                "\n  \"lastName\" : \"Wyatt\"," +
                "\n  \"mealChoice\" : \"calzone\"" +
                "\n} ]";
        try {
            assertEquals(expectedOutput, Files.readString(path));
        } catch (IOException ioException) {
            fail("Caught exception in testWriteOneCustomer - fail test.");
        }
    }

    @Disabled
    @Test
    void testWriteMultipleCustomers() {
        Path path = Paths.get("test-customer5.json");
        customers.add(ben);
        customers.add(leslie);
        customers.add(ron);
        CustomerDriver.writeFile(path.toString(), customers);
        String expectedOutput = "[ {\n" +
                "  \"firstName\" : \"Ben\"," +
                "\n  \"lastName\" : \"Wyatt\"," +
                "\n  \"mealChoice\" : \"calzone\"" +
                "\n}, {\n" +
                "  \"firstName\" : \"Leslie\"," +
                "\n  \"lastName\" : \"Knope\"," +
                "\n  \"mealChoice\" : \"waffles with whipped cream\"" +
                "\n}, {\n" +
                "  \"firstName\" : \"Ron\"," +
                "\n  \"lastName\" : \"Swanson\"," +
                "\n  \"mealChoice\" : \"four-horse meals of the egg-pork-alypse\"" +
                "\n} ]";
        try {
            assertEquals(expectedOutput, Files.readString(path));
        } catch (IOException ioException) {
            fail("Caught exception in testWriteMultipleCustomers - fail test.");
        }
    }

    @Disabled
    @Test
    void testWriteNoCustomers() {
        Path path = Paths.get("test-customer6.json");
        CustomerDriver.writeFile(path.toString(), customers);
        try {
            assertEquals("[ ]", Files.readString(path));
        } catch (IOException ioException) {
            fail("Caught exception in testWriteNoCustomers - fail test.");
        }
    }
}

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JSON Lab

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Unit Tests

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