Nextsync – Native Nextcloud Sync Service with jextract

This project implements a Java-based file synchronization service for Nextcloud using native libraries via the Foreign Function & Memory API (FFM API). Native interactions with libcurl are exposed in Java through automatically generated bindings using jextract.

Overview

• Java 22 with Foreign Function & Memory API
• Native C library (libsync.so) using libcurl and libxml2
• REST API built with Quarkus
• Folder watcher that uploads files on change
• Uses jextract for generating Java bindings (no JNI)

Project Structure

native-worker/ # C source code (sync.c, sync.h) quarkus-service/ # Quarkus-based Java REST service src/main/java/ # jextract-generated Java bindings libsync.so # Compiled native shared library

Features

• Upload local files to Nextcloud via HTTP PUT
• List remote folders using WebDAV PROPFIND
• REST endpoints to trigger upload or folder listing
• File watcher that observes a local directory
• Fully JNI-free native integration using jextract and the FFM API

Building the Project

1. Compile the native library

cd native-worker gcc -fPIC -shared -o libsync.so src/sync.c -lcurl -lxml2

Make sure libsync.so is discoverable via the JVM (e.g., by setting LD_LIBRARY_PATH or placing it in the project root).

### Run jextract

jextract --source \
  --target-package com.nativecloud.sync \
  --output src/main/java \
  -I include \
  include/sync.h

or use the run script run.sh

Start the quarkus service

cd quarkus-service ./mvnw compile quarkus:dev

Environment Variables

The service reads the following environment variables:

Example:

export NEXTCLOUD_URL="https://cloud.example.com/remote.php/dav/files/admin/"
export NEXTCLOUD_USER="admin"
export NEXTCLOUD_PASSWORD="secret"
export WATCH_DIR="/home/user/sync-folder"