Java REST API Client with JDK Http Client and JUnit Tests

Overview

This project demonstrates how to interact with a REST API using the JDK Http Client and how to write JUnit test cases to verify the functionality of the API client. We use a sample Todo API from https://jsonplaceholder.typicode.com/todos to showcase the concepts.

Project Structure

The project is structured as follows:

• Application.java: Contains the main application logic to interact with the Todo API.
• TodoClient.java: The client class responsible for making HTTP requests to the Todo API.
• Todo.java: A record class representing a Todo item.
• TodoNotFoundException.java: A custom exception thrown when a Todo item is not found.
• TodoClientTest.java: JUnit test cases for testing the TodoClient class.

Dependencies

• Jackson: For JSON parsing and serialization.
• JUnit 5: For unit testing.

Code Explanation

Todo.java

A simple record class that represents a Todo item with four fields:

• userId: The ID of the user associated with the Todo.
• id: The ID of the Todo item.
• title: The title of the Todo item.
• completed: A boolean indicating if the Todo item is completed.

TodoClient.java

This class contains methods to interact with the Todo API:

• findAll(): Retrieves a list of all Todo items.
• findById(int id): Retrieves a single Todo item by its ID.
• create(Todo todo): Creates a new Todo item.
• update(Todo todo): Updates an existing Todo item.
• delete(Todo todo): Deletes a Todo item by its ID.

Application.java

The main class that demonstrates how to use TodoClient to fetch and print Todo items. It also prints a message indicating it's time to check the tests.

TodoNotFoundException.java

A custom exception thrown when a Todo item is not found by its ID.

TodoClientTest.java

JUnit test cases for the TodoClient class:

• findAll(): Tests retrieving all Todo items.
• shouldReturnTodoGivenValidId(): Tests retrieving a Todo item by a valid ID.
• shouldThrowNotFoundExceptionGivenInvalidId(): Tests that a TodoNotFoundException is thrown for an invalid ID.
• shouldCreateNewTodo(): Tests creating a new Todo item.
• shouldUpdateExistingNewTodo(): Tests updating an existing Todo item.
• shouldDeleteExistingNewTodo(): Tests deleting a Todo item.