Java Development Bench

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

./scripts/build-layer.sh

This will:

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

2. Start the Container

./setup.sh

3. Open in VS Code

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