📂 FileSentry

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About FileSentry

FileSentry is a lightweight, cross-platform Java library for monitoring file changes in real time.
It provides a simple API built on Java NIO’s WatchService, with built-in debouncing and event callbacks.

Supports Windows, Linux, and macOS.

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✨ Features

✅ Watch any file for changes in real time
✅ Get notified when a file is modified
✅ Easy to integrate into Swing, JavaFX, or command-line apps
✅ Minimal dependencies (pure Java)
✅ Automatically stops when you’re done
✅ Suitable for:

• Text editors (live reload)
• Log viewers
• Developer tools
• Custom synchronization utilities

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🚀 Getting Started

📦 Installation

Maven:

<dependency>
  <groupId>io.github.raghul-tech</groupId>
  <artifactId>filesentry</artifactId>
  <version>1.0.0</version>
</dependency>

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💡 Example Usage

Below is a complete example that:

• Watches sample.txt

• Prints a message when the file changes

• Automatically stops when the program ends

import io.github.raghultech.filesentry.FileWatcher;

import java.io.File;
import java.lang.ref.WeakReference;

/**
 * Example of using FileSentry to monitor file changes.
 */
public class ExampleFileWatcher {

    private FileWatcher fileWatcher;
    private transient WeakReference<Thread> fileWatcherThread;
    private File currentFile = new File("sample.txt"); 

    public void watchFileForChanges() {
        stopFileWatcher(); // Stop previous watcher if running

        if (currentFile == null || !currentFile.exists()) {
            System.out.println("File not found: " + currentFile.getAbsolutePath());
            return;
        }

        fileWatcher = new FileWatcher(currentFile);
        
        // 1️⃣ Simple modify/create/delete awareness
        fileWatcher.setFileModifyListener(changed -> {
            if (changed) {
                System.out.println(" Simple: File changed.");
                // your reload logic 
            }
        });

        // 2️⃣ State listener: existence
        fileWatcher.setFileStateListener(exists -> {
            if (exists) {
                System.out.println(" State: File exists (create/modify).");
            } else {
                System.out.println(" State: File deleted.");
            }
        });

        // 3️⃣ Detailed change type
        fileWatcher.setFileChangeListener(type -> {
            switch (type) {
                case CREATED -> System.out.println(" Detailed: File CREATED.");
                case MODIFIED -> System.out.println("️ Detailed: File MODIFIED.");
                case DELETED -> System.out.println(" Detailed: File DELETED.");
            }
        });

        Thread watcherThread = new Thread(fileWatcher, "FileWatcher-Thread");
        watcherThread.setDaemon(true); // Allow JVM to exit if only daemon threads remain
        fileWatcherThread = new WeakReference<>(watcherThread);
        watcherThread.start();
    }

    public void stopFileWatcher() {
        if (fileWatcher != null) {
            fileWatcher.stopWatching();
        }

        Thread watcherThread = fileWatcherThread != null ? fileWatcherThread.get() : null;
        if (watcherThread != null && watcherThread.isAlive()) {
            watcherThread.interrupt();
            try {
                watcherThread.join(1000); // Wait for thread to exit
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }

    public static void main(String[] args) {
        ExampleFileWatcher watcher = new ExampleFileWatcher();
        watcher.watchFileForChanges();

        // Keep the main thread alive for demonstration
        try {
        	 System.out.println(" Watching file for 60 seconds...");
            Thread.sleep(60000); // Run for 60 seconds
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }

        watcher.stopFileWatcher();
         System.out.println(" Stopped watching.");
    }
}

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📝 Clarify listener behaviors in the Features section

• Just a short note describing exactly what each listener returns, so no confusion (since you had that question earlier):

📝 Note about Listeners

• FileModifyListener: always true on any event (create, modify, delete)
• FileStateListener: true if it is modified or created or file currently exists, false if deleted
• FileChangeListener: returns a FileChangeType enum (CREATED, MODIFIED, DELETED)

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🖥️ How to Run

✅ Using Command Line

1. Compile:

javac -cp filesentry-1.0.0.jar ExampleFileWatcher.java

2.Run:

java -cp .;filesentry-1.0.0.jar ExampleFileWatcher

(On Linux or mac, replace ; with :)

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🧭 Where to Use

• Command-line tools: watch logs or configuration files.

• GUI applications: detect when a file changes and prompt the user to reload.

• Development tools: implement live-reload behavior.

• Scripting: monitor scripts or data files.

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🛠️ Why Use FileSentry?

• Zero configuration: Just point it to a file.

• Cross-platform: Works on Windows, Linux, macOS.

• Small footprint: No heavy dependencies.

• Easy to stop: Clean shutdown with stopWatching().

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✅ Good to Know

• FileSentry uses Java NIO’s WatchService internally.

• To avoid memory leaks, always stop your watcher when you no longer need it.

• You can integrate it into larger apps (editors, tools) by starting/stopping in your app lifecycle hooks.

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🆕 Changelog:

• View all releases on the Releases Page.
• For a detailed log of all changes, refer to the CHANGELOG.md file.

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🤝 Contributing

• We welcome contributions of all kinds:

  • 🛠️ Bug fixes

  • 🌟 Feature suggestions

  • 📚 Documentation improvements

  • 🧪 More usage examples

Please check the Contributing Guide before starting.

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🐞 Report a Bug

• If you've encountered a bug, please report it by clicking the link below. This will guide you through the bug-reporting process: ➡️ Click here to report a bug

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📄 License

• This project is licensed under the MIT License.

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📬 Contact

Email: raghultech.app@gmail.com

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☕ Support

If you find this project useful, consider buying me a coffee!