MCP Server Postgres

MCP Server PostgreSQL

A Model Context Protocol (MCP) server for PostgreSQL built with Spring Boot and Spring AI. This server provides read-only access to PostgreSQL databases through dynamic connections.

✅ Project Status

COMPLETED: The MCP server is fully functional with the following features:

• ✅ Spring Boot 3.4.1 + Spring AI 1.0.0 + Java 21
• ✅ Dynamic PostgreSQL connections (no hardcoded credentials)
• ✅ Read-only query validation and security
• ✅ Complete test suite with Testcontainers
• ✅ Docker Compose setup with sample data
• ✅ Production-ready Dockerfile
• ✅ Comprehensive documentation

Features

• Dynamic Database Connections: Connect to any PostgreSQL database with runtime parameters
• Read-Only Operations: Ensures database safety by only allowing SELECT queries
• MCP Tools:
  • list_schemas: List all schemas in a database
  • list_tables: List all tables in a specific schema
  • select: Select rows from a table with optional conditions and ordering
  • execute_query: Execute read-only SQL queries
• Built with Modern Stack: Spring Boot 3.4.1, Spring AI 1.0.0, Java 21

Quick Start

Prerequisites

• Java 21
• Maven 3.9+
• Docker & Docker Compose (for testing)

Running the Server

1. Clone and build the project:

   git clone https://github.com/luanvuhlu/mcp-server-postgres.git
   cd mcp-server-postgres
   mvn clean compile
   

2. Start test PostgreSQL database:

   docker-compose up -d
   

3. Run the MCP server:

   mvn spring-boot:run
   

The MCP server will start and be ready to accept connections via the Model Context Protocol.

Testing with Sample Data

The Docker Compose setup includes a PostgreSQL instance with sample data:

• Host: localhost
• Port: 5432
• Database: postgres
• Username: postgres
• Password: your_name

Sample schemas and tables are automatically created:

• public schema: users, products
• sales schema: orders, order_items
• inventory schema: stock

Using with MCP Clients

This server can be used with any MCP-compatible client. Here are some examples:

Claude Desktop

Add the following to your Claude Desktop configuration file:

{
  "mcpServers": {
    "postgres": {
      "command": "java",
      "args": ["-jar", "target/mcp-server-postgres-1.0.0-SNAPSHOT.jar"]
    }
  }
}

Other MCP Clients

The server implements the standard MCP protocol and can be used with any compatible client by running:

java -jar target/mcp-server-postgres-1.0.0-SNAPSHOT.jar

MCP Tools Usage

List Schemas

List all schemas in a PostgreSQL database:

{
  "name": "list_schemas",
  "arguments": {
    "host": "localhost",
    "database": "postgres", 
    "username": "postgres",
    "password": "your_name"
  }
}

List Tables

List all tables in a specific schema:

{
  "name": "list_tables",
  "arguments": {
    "host": "localhost",
    "database": "postgres",
    "username": "postgres", 
    "password": "your_name",
    "schema": "public"
  }
}

Select

Select rows from a table with optional conditions and ordering:

{
  "name": "select",
  "arguments": {
    "host": "localhost",
    "database": "postgres",
    "username": "postgres", 
    "password": "your_name",
    "table": "users",
    "schema": "public",
    "conditions": "id > 1",
    "orderBy": "username ASC",
    "limit": 10
  }
}

Execute Query

Execute a read-only SQL query:

{
  "name": "execute_query",
  "arguments": {
    "host": "localhost",
    "database": "postgres",
    "username": "postgres",
    "password": "your_name", 
    "query": "SELECT * FROM users LIMIT 10"
  }
}

Security

• Read-Only: Only SELECT, WITH, SHOW, EXPLAIN, DESCRIBE queries are allowed
• Dynamic Connections: No hardcoded database credentials
• Input Validation: Queries are validated before execution
• Error Handling: Proper error messages without exposing sensitive information

Configuration

Application Properties

Configure the MCP server in src/main/resources/application.yml:

spring:
  ai:
    mcp:
      server:
        enabled: true
        port: 3000

Database Connections

All database connections are dynamic and provided per request. No default database connection is configured.

MCP Server Protocol

This server implements the Model Context Protocol (MCP) specification and communicates via JSON-RPC over stdio or TCP. The server registers the following tools that can be called by MCP-compatible clients.

Development

Project Structure

src/main/java/com/luanvv/mcp/
├── McpServerPostgresApplication.java    # Main application
├── config/
│   └── McpServerConfig.java            # MCP configuration
├── model/
│   └── DatabaseConnection.java         # Connection model
├── service/
│   └── PostgresService.java           # Database operations
└── tools/
    ├── ListSchemaTool.java            # List schemas tool
    ├── ListTablesTool.java           # List tables tool
    ├── SelectTool.java               # Select queries tool
    └── ExecuteQueryTool.java         # Execute query tool

Building

# Compile
mvn clean compile

# Run tests
mvn test

# Package
mvn clean package

# Run
mvn spring-boot:run

Docker

Build and run with Docker:

# Build image
docker build -t mcp-server-postgres .

# Run container
docker run -p 3000:3000 mcp-server-postgres

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests
5. Submit a pull request

License

This project is licensed under the MIT License.

Support

For issues and questions, please use the GitHub issue tracker.