Onjava

This repository contains two main projects demonstrating Java and React integration: a Spring Boot backend and a React frontend.

Projects

Jar (Java Spring Boot Application)

A Spring Boot application with REST endpoints, security configuration, and a message repository.

• Location: jar/
• Main Class: com.jar.jar.JarApplication
• Features:
  • REST API with HelloController
  • User authentication and security (JWT)
  • Message model and repository (JPA)

My React App

A React application that interacts with the Java backend via REST API.

• Location: my-react-app/
• Features:
  • React components
  • API service using Axios for backend communication

Prerequisites

Backend (Jar)

• Java: JDK 21 (or compatible version)
• Maven: 3.6+ (or use included mvnw wrapper)
• Database: H2 (in-memory by default), or MongoDB/SQLite for alternatives

Frontend (My React App)

• Node.js: 16+ (includes npm)
• npm: 7+ (comes with Node.js)

Installation and Setup

Backend Setup

1. Install Java and Maven:

   • Download and install JDK 21 from Adoptium or Oracle.
   • Maven can be installed from maven.apache.org, or use the included mvnw script.

2. Navigate to the backend directory:

   cd jar

3. Build the application (optional, as Spring Boot handles it):

   ./mvnw clean install

Frontend Setup

1. Install Node.js and npm:

   • Download from nodejs.org.

2. Navigate to the frontend directory:

   cd my-react-app

3. Install dependencies:

   npm install

Running Locally

Start the Backend

1. Ensure you're in the jar directory.
2. Run the application:

   ./mvnw spring-boot:run

   • The app will start on http://localhost:8080.
   • H2 console available at http://localhost:8080/h2-console (login with JDBC URL: jdbc:h2:mem:testdb, username: sa, password: empty).

Start the Frontend

1. Ensure you're in the my-react-app directory.
2. Start the development server:

   npm start

   • The app will open at http://localhost:3000.

Database Configuration

Local In-Memory Database (H2 - Default)

The application uses H2 in-memory database by default. No additional setup required. Data is lost on restart.

Switching to SQLite (Local File-Based)

1. Add SQLite dependency to pom.xml:

   <dependency>
       <groupId>org.xerial</groupId>
       <artifactId>sqlite-jdbc</artifactId>
       <version>3.42.0.0</version>
   </dependency>

2. Update application.properties:

   spring.datasource.url=jdbc:sqlite:database.db
   spring.datasource.driverClassName=org.sqlite.JDBC
   spring.jpa.database-platform=org.hibernate.community.dialect.SQLiteDialect
   spring.h2.console.enabled=false

3. Create the database file (optional, JPA will create it).

Switching to MongoDB (Cloud/Local)

1. Add MongoDB dependency to pom.xml:

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-mongodb</artifactId>
   </dependency>

   Remove H2 dependency if not needed.

2. Update application.properties:

   spring.data.mongodb.uri=mongodb://localhost:27017/yourdb
   # For cloud MongoDB Atlas, use:
   # spring.data.mongodb.uri=mongodb+srv://username:password@cluster.mongodb.net/yourdb

3. For local MongoDB:

   • Install MongoDB from mongodb.com.
   • Start MongoDB service.

4. For cloud MongoDB:

   • Sign up at MongoDB Atlas.
   • Create a cluster and get the connection string.

Note: Switching to MongoDB requires changing the repository from JPA to MongoRepository if using document-based storage.

API Endpoints

• GET /api/hello - Hello endpoint
• Other endpoints as defined in controllers.

Contributing

Feel free to contribute to either project. Ensure both frontend and backend are tested locally before submitting PRs.