Java Filesystem & Web MCP Server

This project implements a Model Context Protocol (MCP) server that provides filesystem operations and web access tools for Large Language Model (LLM) agents. It enables AI assistants to interact with both the local filesystem and web resources through a set of well-defined operations.

Features

The server provides the following operations:

Filesystem Operations

• Reading Files: Read the complete contents of a file with proper encoding detection
• Writing Files: Create or overwrite files with new content
• Editing Files: Make line-based edits with git-style diff generation
• Searching Files: Recursively search for files and directories using glob patterns
• Listing Directories: Get detailed listings of directory contents
• Directory Creation: Create directories and nested directory structures
• Grep Files: Search for text patterns within files with line numbers and context, similar to Unix grep command
• Bash Command: Execute bash commands in the system shell and capture their output

Web Operations

• Web Page Fetching: Retrieve content from web pages with configurable timeouts
• HTML Content Extraction: Extract text content from HTML documents

These operations are exposed as tools for Large Language Models using the Model Context Protocol (MCP), allowing AI systems to safely interact with the filesystem and access web resources.

Example of the MCP Java tool with DevoxxGenie

Getting Started

Prerequisites

• Java 17 or higher
• Maven 3.6+
• Spring Boot 3.3.6
• Spring AI MCP Server components

Building the Project

Build the project using Maven:

mvn clean package

Running the Server

The server supports two transport modes:

SSE Mode (HTTP-based, default)

Run the server for SSE-based communication:

java -jar target/devoxx-filesystem-0.0.1-SNAPSHOT.jar

This starts an HTTP server on port 8081 with the SSE endpoint at /sse.

STDIO Mode (for MCP clients like Claude Desktop or DevoxxGenie)

For STDIO-based communication (required by most MCP clients):

java -Dspring.ai.mcp.server.stdio=true \
     -Dspring.main.web-application-type=none \
     -Dspring.main.banner-mode=off \
     -Dlogging.pattern.console= \
     -jar target/devoxx-filesystem-0.0.1-SNAPSHOT.jar

Important flags for STDIO mode:

• -Dspring.ai.mcp.server.stdio=true - Enables STDIO transport
• -Dspring.main.web-application-type=none - Disables the web server
• -Dspring.main.banner-mode=off - Disables Spring Boot banner (required to avoid corrupting JSON-RPC communication)
• -Dlogging.pattern.console= - Disables console logging

Tool Services

Filesystem Tools

ReadFileService

readFile(String fullPathFile)

Reads the complete contents of a file from the file system. Handles various text encodings and provides detailed error messages if the file cannot be read.

WriteFileService

writeFile(String path, String content)

Creates a new file or completely overwrites an existing file with new content. Creates parent directories if they don't exist.

EditFileService

editFile(String path, String edits, Boolean dryRun)

Makes line-based edits to a text file. Each edit replaces exact line sequences with new content. Returns a git-style diff showing the changes made. The dryRun parameter allows viewing changes without applying them.

SearchFilesService

searchFiles(String path, String pattern)

Recursively searches for files and directories matching a pattern. Searches through all subdirectories from the starting path. The search is case-insensitive and matches partial names.

ListDirectoryService

listDirectory(String path)

Gets a detailed listing of all files and directories in a specified path. Results clearly distinguish between files and directories with additional metadata.

GrepFilesService

grepFiles(String directory, String pattern, String fileExtension, Boolean useRegex, Integer contextLines, Integer maxResults, Boolean ignoreCase)

Searches for text patterns within files. Returns matching files with line numbers and context. Similar to the Unix 'grep' command but with additional features for context display. Supports regex patterns, case-insensitive search, and context lines before/after matches.

CreateDirectoryService

createDirectory(List<String> directories)

Creates new directories or ensures that directories exist. Can create multiple directories in one operation. If a directory already exists, the operation succeeds silently. Perfect for setting up directory structures for projects or ensuring required paths exist.

BashService

executeBash(String command, String workingDirectory, Integer timeoutSeconds)

Execute a Bash command in the system shell and return the output. This tool allows running system commands and capturing their standard output and error streams. Use with caution as some commands may have system-wide effects.

Web Tools

FetchWebpageService

fetchWebpage(String url, Integer timeoutMs)

Fetches or reads a webpage from a URL and returns its content. The service uses jsoup to connect to the webpage and retrieve its content. The optional timeoutMs parameter allows setting a custom connection timeout.

Testing

Running Unit Tests

A comprehensive set of unit tests is provided for all service classes. Run them using:

mvn test

The tests use JUnit 5 and Mockito for mocking external dependencies like the jsoup library for web requests.

Running Integration Tests

Integration tests verify the STDIO transport by spawning the server as a subprocess. First build the JAR, then run integration tests:

mvn package -DskipTests
mvn test -Pintegration-tests

Test Clients

Test clients are provided to demonstrate MCP protocol usage:

• ClientStdio.java - Demonstrates STDIO transport communication
• ClientSse.java - Demonstrates SSE transport communication

Configuration

The application is configured via application.properties:

spring.main.web-application-type=none
spring.main.banner-mode=off
logging.pattern.console=

spring.ai.mcp.server.name=filesystem-server
spring.ai.mcp.server.version=0.0.1

logging.file.name=,/JavaFileSystemMCP/target/filesystem-server.log

Project Structure

JavaFileSystemMCP/
  src/
    main/
      java/
        com/
          devoxx/
            mcp/
              filesystem/
                tools/
                  EditFileService.java
                  ReadFileService.java
                  WriteFileService.java
                  SearchFilesService.java
                  FetchWebpageService.java
                  ListDirectoryService.java
                  CreateDirectoryService.java
                  GrepFilesService.java
                  BashService.java
                McpServerApplication.java
      resources/
        application.properties
    test/
      java/
        com/
          devoxx/
            mcp/
              filesystem/
                tools/
                  ReadFileServiceTest.java
                  WriteFileServiceTest.java
                  EditFileServiceTest.java
                  SearchFilesServiceTest.java
                  FetchWebpageServiceTest.java
                  ListDirectoryServiceTest.java
                  CreateDirectoryServiceTest.java
                  GrepFilesServiceTest.java
                ClientStdio.java
  pom.xml
  README.md

Dependencies

The project uses:

• Spring Boot 3.3.6
• Spring AI MCP Server Components
• Jackson for JSON processing
• jsoup for HTML parsing and web content retrieval
• JUnit 5 and Mockito for testing

Implementation Notes

• The server is designed to operate using the STDIO transport mechanism
• Banner mode and console logging are disabled to allow the STDIO transport to work properly
• Error handling provides detailed information about issues encountered during operations
• Each tool service includes comprehensive error handling and returns results in a standardized JSON format
• The EditFileService includes sophisticated diff generation for tracking changes
• The SearchFilesService supports glob patterns for flexible file matching
• The FetchWebpageService includes configurable timeouts and robust error handling for web requests

Integration with DevoxxGenie MCP Support

This server can be easily integrated with DevoxxGenie using the MCP (Model Context Protocol) support. Here's how to set it up:

Configuration in DevoxxGenie

1. In DevoxxGenie, access the MCP Server configuration screen
2. Configure the server with the following settings:

   • Name: JavaFilesystem (or any descriptive name)

   • Transport Type: STDIO

   • Command: Full path to your Java executable (e.g., /Library/Java/JavaVirtualMachines/liberica-jdk-23.jdk/Contents/Home/bin/java)

   • Arguments:

     -Dspring.ai.mcp.server.stdio=true
     -Dspring.main.web-application-type=none
     -Dspring.main.banner-mode=off
     -Dlogging.pattern.console=
     -jar
     ~/JavaFileSystemMCP/target/devoxx-filesystem-0.0.1-SNAPSHOT.jar
     

     Enter each argument on a new line. You may need to change the path for -jar to point to where you've built the jar.

     Important: The -Dspring.main.banner-mode=off flag is required to disable the Spring Boot banner, which would otherwise interfere with the JSON-RPC communication over STDIO.

Usage with DevoxxGenie

Once configured, DevoxxGenie will automatically discover the tools provided by this MCP server. The AI assistant can then use these tools to:

1. Read and write files on the local system
2. Search for files and directories
3. List directory contents
4. Make edits to existing files
5. Search for text patterns within files (grep)
6. Create directories and nested directory structures
7. Execute bash commands in the system shell
8. Fetch web pages and extract content

All operations will be performed with the permissions of the user running the DevoxxGenie application.

Using with Claude Desktop

Edit your claude_desktop_config.json file with the following:

{
  "mcpServers": {
    "filesystem": {
      "command": "/Library/Java/JavaVirtualMachines/liberica-jdk-23.jdk/Contents/Home/bin/java",
      "args": [
        "-Dspring.ai.mcp.server.stdio=true",
        "-Dspring.main.web-application-type=none",
        "-Dspring.main.banner-mode=off",
        "-Dlogging.pattern.console=",
        "-jar",
        "~/JavaFileSystemMCP/target/devoxx-filesystem-0.0.1-SNAPSHOT.jar"
      ]
    }
  }
}

You may need to change the path for -jar to point to where you've built the jar.

Important: The -Dspring.main.banner-mode=off flag is required to disable the Spring Boot banner, which would otherwise interfere with the JSON-RPC communication over STDIO.

Security Considerations

When using this server, be aware that:

• The LLM agent will have access to read and write files on the host system
• The agent can execute bash commands with the permissions of the user running the application
• The agent can fetch content from any accessible web URL
• Consider running the server with appropriate permissions and in a controlled environment
• The server does not implement authentication or authorization mechanisms
• Consider network firewall rules if restricting web access is required