JHRJava

Java Hot Reload / docs

Save. Recompile. Restart. Automatically.

Overview

JHR (Java Hot Reload) watches your source tree, recompiles when .java files change, and restarts your program automatically. It is designed for tight feedback loops during development.

InfoJHR uses javac/java directly and shows a desktop overlay window whenever compilation fails.

What it does

Watches your source directory with debouncing to avoid rebuild storms.
Compiles updated files with javac on every save.
Restarts the running process so changes are reflected immediately.
Shows errors in an always-on-top Swing overlay window.

Installation

Download Release Setup

Download the latest release Setup

Download latest releaseFile: JavaHotReloaderSetup.exe

Run the installer and follow the prompts

Run the binary

powershell
jhr --help

Download Release Binary

Download the latest release ZIP

Download latest releaseFile: JavaHotReloader.zip

Extract the files into a folder
Add the folder to your PATH

Run the binary

powershell
jhr --help

Build from source

bash
git clone https://github.com/JasnRathore/jhr
cd jhr

powershell
buildjar.ps1

This produces target/jhr.jar and the target/jhr launcher script.

powershell
buildexe.ps1

This produces release/jhr.exe and the required files in release

powershell
cd release
./jhr.exe --help

Quick Start

From your Java project directory, initialize a config file and start JHR:

bash
jhr init

ini
root = src
main_class = com.example.Main
classpath = src
delay = 1000

bash
jhr

Configuration

Key	Default	Description
root	src	Source directory to watch
watch_dirs	.	Comma-separated subdirectories to watch
watch_exts	.java	File extensions that trigger rebuild
exclude_dirs	.git,tmp,vendor,target,build	Directories to ignore
main_class	Demo	Fully-qualified main class to run
classpath	src	Classpath for javac/java
javac_flags	(empty)	Extra javac flags
jvm_args	(empty)	JVM flags like -Xmx
delay	1000	Debounce delay in ms
build_cmd	(empty)	Optional custom build command
log_level	info	debug \| info \| warn \| error

TipUse build_cmd for multi-module projects that need custom build steps.

Commands

Command	Description
jhr	Start hot-reload using .jhr.conf
jhr init	Generate a default .jhr.conf
jhr version	Print version info
jhr help	Show usage

Error Overlay

When compilation fails, JHR opens an always-on-top Swing window with the full javac output. Once you fix the error and save, the overlay dismisses automatically.

Shows the file and line that failed to compile.
Displays full stderr output in a scrollable panel.
Auto-hides on the next successful rebuild.

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