diwang01/spring-mcp-server

Spring MCP Server

A modern Model Context Protocol (MCP) server implementation using Spring Framework and Java 21.

Features

• ✨ Java 21: Leverages latest Java features (records, sealed classes, pattern matching, switch expressions)
• 🚀 Spring Boot 3.3+: Modern Spring Framework with full dependency injection
• 🔧 MCP Protocol: Implements tools, resources, and prompts
• 🧪 Well-Tested: Comprehensive unit tests with JUnit 5
• 📦 Maven Build: Easy dependency management and building

Architecture

Clean Code Principles Applied

1. Records for Immutability: All DTOs use Java records for concise, immutable data structures
2. Sealed Classes: Type-safe hierarchies with compile-time exhaustiveness
3. Functional Programming: Optional, Stream API, and functional error handling
4. SOLID Principles: Single responsibility, dependency injection, interface segregation
5. Modern Switch Expressions: Pattern matching for cleaner conditional logic

Project Structure

src/main/java/com/example/mcp/
├── McpServerApplication.java          # Main application entry point
├── config/
│   └── McpServerConfig.java          # MCP server configuration
├── tool/
│   ├── EchoTool.java                 # Example tool: echo messages
│   └── DateTimeTool.java             # Example tool: date/time operations
├── resource/
│   └── SystemInfoResource.java       # Example resource: system information
└── prompt/
    └── TemplatePromptProvider.java   # Example prompts: code review templates

Components

Tools

• EchoTool: Demonstrates string manipulation with optional parameters
• DateTimeTool: Shows timezone handling and date formatting with error handling

Resources

• SystemInfoResource: Provides JVM and system runtime information using sealed classes

Prompts

• TemplatePromptProvider: Code review and explanation templates with functional composition

Building

mvn clean package

Running

mvn spring-boot:run

Testing

mvn test

Java 21 Features Used

Records

public record EchoInput(String message, String prefix) {}

Sealed Classes

public sealed interface SystemInfo permits JavaInfo, RuntimeInfo, MemoryInfo {}

Pattern Matching

return switch (info) {
    case JavaInfo java -> formatJava(java);
    case RuntimeInfo rt -> formatRuntime(rt);
    case MemoryInfo mem -> formatMemory(mem);
};

Text Blocks

String template = """
    Please review the following code:
    {{code}}
    """;

Dependencies

• Spring Boot 3.3.5
• Spring AI MCP (Milestone)
• Java 21
• JUnit 5
• AssertJ

Best Practices

1. Null Safety: Using Optional for nullable values
2. Immutability: Records and List.copyOf() for defensive copying
3. Error Handling: Functional error handling without exceptions where possible
4. Thread Safety: Immutable data structures by default
5. Dependency Injection: Constructor injection with Spring
6. Testing: Parameterized tests for comprehensive coverage

License

MIT License