boot-data-multipledatasources

Multiple Datasource's with Parallel Data Fetching

This Spring Boot application demonstrates how to work with multiple datasources and implement efficient parallel data fetching.

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Features

• Multiple database connections (PostgreSQL and MySQL)
• Parallel data fetching using CompletableFuture
• Database migrations using both Liquibase and Flyway
• Exception handling with Problem Details
• Virtual Threads support
• Swagger API documentation

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Architecture

Database Setup

• PostgreSQL Database: Stores member information
  • Managed by Liquibase migrations
  • Uses sequence-based ID generation
• MySQL Database: Stores cardholder information
  • Managed by Flyway migrations
  • Uses identity-based ID generation

Key Components

• DetailsService: Implements parallel data fetching
  • Uses CompletableFuture for asynchronous operations
  • Implements timeout handling (5 seconds)
  • Provides comprehensive error handling
• Data Models:
  • Member: Core member information (PostgreSQL)
  • CardHolder: Card-related information (MySQL)
• Exception Handling:
  • CustomServiceException: For service-layer errors
  • MemberNotFoundException: For missing member scenarios
  • Problem Details support for standardized error responses

Configuration

PostgreSQL Configuration

spring.datasource.url=jdbc:postgresql://localhost:5432/memberdb
spring.datasource.username=postgres
spring.datasource.password=postgres

MySQL Configuration

app.datasource.cardholder.url=jdbc:mysql://localhost:3306/cardholderdb
app.datasource.cardholder.username=user
app.datasource.cardholder.password=password

Getting Started

1. Start PostgreSQL and MySQL databases
2. Configure database connections in application.properties
3. Run the application: The databases will be automatically initialized
4. Access Swagger UI: http://localhost:8080/swagger-ui.html

Implementation Notes

• Database migrations run automatically on startup
• Data bootstrapping occurs via ApplicationReadyEvent
• Parallel data fetching implemented using Spring's @Qualifier("applicationTaskExecutor")
• Virtual Threads enabled for improved scalability
• HikariCP connection pooling with optimized settings
• Automatic commit disabled for better transaction control

API Endpoints

• GET /api/details/{memberId}: Fetches member details from both databases in parallel
  • Returns combined information from both datasource's
  • Implements timeout handling (5 seconds)
  • Returns standardized error responses using Problem Details

Testing

• Integration tests demonstrate concurrent request handling
• MockMvcTester used for API testing
• Testcontainers with parallel startup for database testing