Overview

Java SDK for the Model Context Protocol enables standardized integration between AI models and tools.

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Features

• MCP Client and MCP Server implementations supporting:
  • Protocol version compatibility negotiation
  • Tool discovery, execution, list change notifications
  • Resource management with URI templates
  • Roots list management and notifications
  • Prompt handling and management
  • Sampling support for AI model interactions
• Multiple transport implementations:
  • Default transports (included in core mcp module, no external web frameworks required):
    • Stdio-based transport for process-based communication
    • Java HttpClient-based SSE client transport for HTTP SSE Client-side streaming
    • Servlet-based SSE server transport for HTTP SSE Server streaming
  • Optional Spring-based transports (convenience if using Spring Framework):
    • WebFlux SSE client and server transports for reactive HTTP streaming
    • WebMVC SSE transport for servlet-based HTTP streaming
• Supports Synchronous and Asynchronous programming paradigms

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Architecture

The SDK follows a layered architecture with clear separation of concerns:

• Client/Server Layer (McpClient/McpServer): Both use McpSession for sync/async operations, with McpClient handling client-side protocol operations and McpServer managing server-side protocol operations.
• Session Layer (McpSession): Manages communication patterns and state using DefaultMcpSession implementation.
• Transport Layer (McpTransport): Handles JSON-RPC message serialization/deserialization via:
  • StdioTransport (stdin/stdout) in the core module
  • HTTP SSE transports in dedicated transport modules (Java HttpClient, Spring WebFlux, Spring WebMVC)

The MCP Client is a key component in the Model Context Protocol (MCP) architecture, responsible for establishing and managing connections with MCP servers. It implements the client-side of the protocol.

The MCP Server is a foundational component in the Model Context Protocol (MCP) architecture that provides tools, resources, and capabilities to clients. It implements the server-side of the protocol.

Key Interactions:

• Client/Server Initialization: Transport setup, protocol compatibility check, capability negotiation, and implementation details exchange.
• Message Flow: JSON-RPC message handling with validation, type-safe response processing, and error handling.
• Resource Management: Resource discovery, URI template-based access, subscription system, and content retrieval.

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Dependencies

Add the following Maven dependency to your project:

<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp</artifactId>
</dependency>

<!-- Optional: Spring WebFlux-based SSE client and server transport -->
<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp-spring-webflux</artifactId>
</dependency>

<!-- Optional: Spring WebMVC-based SSE server transport -->
<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp-spring-webmvc</artifactId>
</dependency>

<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp</artifactId>
</dependency>

<!-- Optional: Spring WebFlux-based SSE client and server transport -->
<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp-spring-webflux</artifactId>
</dependency>

<!-- Optional: Spring WebMVC-based SSE server transport -->
<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp-spring-webmvc</artifactId>
</dependency>

dependencies {
  implementation platform("io.modelcontextprotocol.sdk:mcp")
  //...
}

// Optional: Spring WebFlux-based SSE client and server transport
dependencies {
  implementation platform("io.modelcontextprotocol.sdk:mcp-spring-webflux")
}

// Optional: Spring WebMVC-based SSE server transport
dependencies {
  implementation platform("io.modelcontextprotocol.sdk:mcp-spring-webmvc")
}

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Bill of Materials (BOM)

The Bill of Materials (BOM) declares the recommended versions of all the dependencies used by a given release. Using the BOM from your application’s build script avoids the need for you to specify and maintain the dependency versions yourself. Instead, the version of the BOM you’re using determines the utilized dependency versions. It also ensures that you’re using supported and tested versions of the dependencies by default, unless you choose to override them.

Add the BOM to your project:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>io.modelcontextprotocol.sdk</groupId>
            <artifactId>mcp-bom</artifactId>
            <version>0.9.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>io.modelcontextprotocol.sdk</groupId>
            <artifactId>mcp-bom</artifactId>
            <version>0.9.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

dependencies {
  implementation platform("io.modelcontextprotocol.sdk:mcp-bom:0.9.0")
  //...
}

Replace the version number with the version of the BOM you want to use.

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Available Dependencies

The following dependencies are available and managed by the BOM:

• Core Dependencies
  • io.modelcontextprotocol.sdk:mcp - Core MCP library providing the base functionality and APIs for Model Context Protocol implementation, including default STDIO and SSE client and server transport implementations. No external web frameworks required.
• Optional Transport Dependencies (convenience if using Spring Framework)
  • io.modelcontextprotocol.sdk:mcp-spring-webflux - WebFlux-based Server-Sent Events (SSE) transport implementation for reactive applications.
  • io.modelcontextprotocol.sdk:mcp-spring-webmvc - WebMVC-based Server-Sent Events (SSE) transport implementation for servlet-based applications.
• Testing Dependencies
  • io.modelcontextprotocol.sdk:mcp-test - Testing utilities and support for MCP-based applications.