【Java超入門】ファイル同期アプリを自作！WatchServiceで簡単リアルタイム更新対応

"It's a pain to copy folders manually every time."
"I want to sync locally without using USB or the cloud."
The solution to such problems isA custom file synchronization app using Javais.

Specify the folder to be synchronized,Automatically copy new and updated files onlyBy doing so,
You can have your own backup app.

In this article,A file sync app that anyone can easily createof,
We will explain it in an easy-to-understand manner with actual code.

table of contents

What is a file sync app?
1. A handy tool to automate your daily manual copying
Understand the basic configuration of the sync app
1. There are three required features:
The foundation of synchronization: FileUtils.java
Implementation of the main process: FileSyncApp.java
Common errors and how to fix them
1. How to make the app not crash due to errors
Adding application functions makes it even more practical
1. Version control and logging are also possible.
Summary of the final configuration
Summary: Efficient file management with Java

What is a file sync app?

A handy tool to automate your daily manual copying

Conclusion: It is a system that automatically copies files in a folder to another folder.

Manual backups are tedious and error-prone.
If you have a file sync app,Monitor updates and creations in specific folders and copy them automaticallyThey will do it for you.

The Ministry of Internal Affairs and Communications' Information and Communications White Paper also states:Data preservation, automation, and efficiencyThe importance of has been suggested.
(Source: https://www.soumu.go.jp/johotsusintokei/whitepaper/ja/r05/html/)

Understand the basic configuration of the sync app

There are three required features:

Conclusion: You can create a simple sync app with just these three things:

Specifying the folder to be monitored
Detecting new and changed files
Reflection process to destination folder

Configuration diagram:

The foundation of synchronization: FileUtils.java

Implementation of the main process: FileSyncApp.java

1	`);` `(` `; } } }`

Common errors and how to fix them

How to make the app not crash due to errors

File is locked and copy fails
Solution: Wait a few seconds and retry
If the folder does not exist, an exception is thrown.
Solution:Files.createDirectories()Generate it in advance with
It stops at an event that is not included
Solution:event.kind() Log and ignore unnecessary ones.

Adding application functions makes it even more practical

Version control and logging are also possible.

Dated backup saves
Writing to a log file
ENTRY_DELETEMonitor and delete
Full synchronization periodically using a timer (method that does not use WatchService)