README.md

MongoDB CRUD Project with Spring Boot 3.4.0 and Java 21

Project Overview

This is a simple CRUD (Create, Read, Update, Delete) project that demonstrates how to use MongoDB as the database with Spring Boot 3.4.0 and Java 21. The application allows you to register, update, retrieve, and delete pet records. It's designed to be beginner-friendly project.

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Technologies Used

• Java: Version 21
• Spring Boot: Version 3.4.0
• MongoDB: NoSQL Database version 8.0
• Maven: Dependency Management

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Key Notes

Deprecation of @MockBean

As of Spring Boot 3.4.0, the @MockBean annotation for tests has been deprecated, and it will be removed in 3.6.0 . The replacement is the @MockitoBean annotation provided by org.springframework.test.context.bean.override.mockito.MockitoBean.

Example:

// Deprecated
@MockBean
private MyService myService;

// Replacement
@MockitoBean
private MyService myService;

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Advantages of NoSQL Databases

1. Schema Flexibility: MongoDB allows you to store data without a fixed schema, making it easier to adapt to changing application requirements.
2. Horizontal Scalability: NoSQL databases like MongoDB scale out easily by adding more servers.
3. High Performance: Optimized for read and write operations, especially for large volumes of unstructured data.
4. Support for Complex Data Types: MongoDB natively handles hierarchical relationships and embedded documents.
5. Cost Efficiency: Open-source nature and flexibility often reduce infrastructure costs compared to traditional databases.

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Relational vs. MongoDB Command Comparison

Operation	Relational Database	MongoDB
Find	SELECT * FROM table WHERE id = ?	db.collection.find({ _id: value })
Insert	INSERT INTO table (columns) VALUES (?)	db.collection.insertOne({ field: value })
Update	UPDATE table SET field = ? WHERE id = ?	db.collection.updateOne({ _id: value }, { $set: { field: value } })
Delete	DELETE FROM table WHERE id = ?	db.collection.deleteOne({ _id: value })
Join	SELECT * FROM A JOIN B ON A.key = B.key	MongoDB uses $lookup for joins: { $lookup: { from: "B", localField: "key", foreignField: "key", as: "joinedData" } }

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How to Run

Prerequisites

1. Java 21 installed
2. MongoDB running locally or in a Docker container
3. Maven installed

Steps

1. Clone the repository:

   git clone https://github.com/lmaruyama/mongodb-crud.git

2. Navigate to the project directory:

   cd mongodb-crud

3. Run the application:

   ./mvnw spring-boot:run

4. The application will be available at http://localhost:8080/api/v1/pets.

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API Endpoints

Method	Endpoint	Description
POST	/api/v1/pets	Create a new pet
GET	/api/v1/pets	Get all pets
GET	/api/v1/pets/{id}	Get a pet by ID
GET	/api/v1/pets/{type}/type	Get a pet by type [DOG or CAT]
PUT	/api/v1/pets/{id}	Update a pet by ID
DELETE	/api/v1/pets/{id}	Delete a pet by ID

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Testing

The application includes unit tests for the controller layer. Mocking is handled using the new @MockitoBean annotation.

To run tests:

./mvnw test

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Why MongoDB?

MongoDB is an excellent choice for modern applications due to its scalability, performance, and flexibility. It fits particularly well in applications where the data structure evolves frequently or hierarchical relationships are common.