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GitHub - opensoft/javaBench: heavy Java container for Java Development

A comprehensive Java development environment using layered Docker containers.

Features

Java Development Stack

  • OpenJDK 21 (LTS version)
  • Maven - Dependency management and build tool
  • Gradle 8.5 - Modern build automation
  • Spring Boot CLI - Spring application scaffolding
  • SDKMan - Java version management

Development Tools

  • Git, Docker, and common development utilities (from base layer)
  • VS Code Java extension pack support
  • Maven and Gradle caching for faster builds
  • Persistent M2 repository at /workspace/m2repo

Ports

  • 8080 - Spring Boot default port
  • 8081 - Alternative web application port
  • 5005 - Java remote debugging port
  • 9090 - Metrics/Actuator endpoints

Quick Start

1. Build the Image

This will:

  • Check for devbench-base:${USER} (build if needed)
  • Build the Java-specific layer (java-bench:${USER})

2. Start the Container

3. Open in VS Code

Then select "Reopen in Container" from the command palette.

Architecture

Layered Build System

  • Layer 1 (devbench-base): Common development tools
  • Layer 2 (java-bench): Java-specific packages and tools

Benefits:

  • Faster rebuilds (only Layer 2 changes)
  • Shared base across all benches
  • Better Docker layer caching

Usage

Maven Projects

# Create new Maven project
mvn archetype:generate -DgroupId=com.example -DartifactId=my-app

# Build and package
mvn-package  # alias for: mvn clean package

# Run tests
mvn-test

Gradle Projects

# Create new Gradle project
gradle init

# Build project
gradle-build  # alias for: gradle build

# Run tests
gradle-test

Spring Boot Projects

# Create new Spring Boot project
spring init --dependencies=web,data-jpa my-spring-app

# Run Spring Boot application
spring-run  # alias for: ./mvnw spring-boot:run

SDKMan

# List available Java versions
sdk list java

# Install a specific Java version
sdk install java 17.0.9-tem

# Switch Java version
sdk use java 17.0.9-tem

Directory Structure

/workspace/
├── projects/      # Your Java projects
├── m2repo/        # Maven repository cache
└── .gradle/       # Gradle cache

Configuration

Maven Settings

Maven is configured to use /workspace/m2repo for the local repository, persisting dependencies across container restarts.

Environment Variables

  • JAVA_HOME: /usr/lib/jvm/java-21-openjdk-amd64
  • GRADLE_HOME: /opt/gradle/gradle-8.5
  • MAVEN_OPTS: -Dmaven.repo.local=/workspace/m2repo

Useful Aliases

  • mvn-clean - Clean Maven project
  • mvn-package - Clean and package
  • mvn-install - Clean and install
  • mvn-test - Run tests
  • gradle-build - Build Gradle project
  • gradle-clean - Clean Gradle project
  • gradle-test - Run Gradle tests
  • spring-run - Run Spring Boot app

Troubleshooting

Container won't start

# Check if image exists
docker images | grep java-bench

# Rebuild if needed
./scripts/build-layer.sh

Maven dependencies not downloading

# Check Maven settings
cat ~/.m2/settings.xml

# Clear cache if needed
rm -rf /workspace/m2repo/*

Java version issues

# Verify Java version
java -version

# Check JAVA_HOME
echo $JAVA_HOME

Version Information

  • Container Version: 1.0.0
  • Base Image: devbench-base
  • JDK Version: OpenJDK 21
  • Maven Version: (from apt)
  • Gradle Version: 8.5
  • Spring Boot CLI: 3.2.0