
Java Docker
- 235 installs
- 40 repo stars
- Updated January 5, 2026
- pluginagentmarketplace/custom-plugin-java
Containerize Java apps with optimized Dockerfiles, JVM tuning, health checks, and multi-stage builds for repeatable staging and production deployments.
About
Covers Dockerizing Java applications end-to-end: efficient multi-stage images, JVM tuning in containers, health probes, and deployment-ready configs for cloud or on-prem runtimes.
- Multi-stage Java Dockerfile templates
- JVM heap and GC container tuning
- Health-check and graceful shutdown hooks
- Layer caching and image slimming tactics
- Orchestrator-ready compose configurations
Java Docker by the numbers
- 235 all-time installs (skills.sh)
- +4 installs in the week ending Aug 4, 2026 (Skillselion tracking)
- Ranked #371 of 1,435 DevOps & CI/CD skills by installs in the Skillselion catalog
- Data as of Aug 4, 2026 (Skillselion catalog sync)
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| Installs | 235 |
|---|---|
| repo stars | ★ 40 |
| Last updated | January 5, 2026 |
| Repository | pluginagentmarketplace/custom-plugin-java ↗ |
What it does
Containerize Java apps with optimized Dockerfiles, JVM tuning, health checks, and multi-stage builds for repeatable staging and production deployments.
Files
Java Docker Skill
Containerize Java applications with optimized Dockerfiles and JVM settings.
Overview
This skill covers Docker best practices for Java including multi-stage builds, JVM container settings, security hardening, and layer optimization.
When to Use This Skill
Use when you need to:
- Create optimized Java Dockerfiles
- Configure JVM for containers
- Implement security best practices
- Reduce image size
- Set up health checks
Topics Covered
Dockerfile Optimization
- Multi-stage builds
- Layer caching strategy
- Spring Boot layered JARs
- Dependency caching
JVM Container Settings
- UseContainerSupport
- MaxRAMPercentage
- GC selection
- Exit on OOM
Security
- Non-root users
- Read-only filesystem
- Vulnerability scanning
- Secrets handling
Quick Reference
# Multi-stage optimized Dockerfile
FROM eclipse-temurin:21-jdk-alpine AS builder
WORKDIR /app
# Cache dependencies
COPY pom.xml .
COPY .mvn .mvn
RUN mvn dependency:go-offline -B
# Build and extract layers
COPY src ./src
RUN mvn package -DskipTests && \
java -Djarmode=layertools -jar target/*.jar extract
# Runtime stage
FROM eclipse-temurin:21-jre-alpine
# Security: non-root user
RUN addgroup -S app && adduser -S app -G app
USER app
WORKDIR /app
# Copy layers in order of change frequency
COPY --from=builder /app/dependencies/ ./
COPY --from=builder /app/spring-boot-loader/ ./
COPY --from=builder /app/snapshot-dependencies/ ./
COPY --from=builder /app/application/ ./
# JVM container settings
ENV JAVA_OPTS="-XX:+UseContainerSupport \
-XX:MaxRAMPercentage=75.0 \
-XX:+ExitOnOutOfMemoryError \
-XX:+UseG1GC"
EXPOSE 8080
HEALTHCHECK --interval=30s --timeout=3s --start-period=30s \
CMD wget -qO- http://localhost:8080/actuator/health/liveness || exit 1
ENTRYPOINT ["sh", "-c", "java $JAVA_OPTS org.springframework.boot.loader.launch.JarLauncher"]JVM Container Flags
# Recommended production settings
JAVA_OPTS="
-XX:+UseContainerSupport
-XX:MaxRAMPercentage=75.0
-XX:InitialRAMPercentage=50.0
-XX:+ExitOnOutOfMemoryError
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/tmp/heapdump.hprof
-XX:+UseG1GC
-Djava.security.egd=file:/dev/./urandom
"Base Image Comparison
| Image | Size | Security | Use Case |
|---|---|---|---|
| temurin:21-jre | ~200MB | Good | General use |
| temurin:21-jre-alpine | ~100MB | Good | Size-optimized |
| distroless/java21 | ~80MB | Best | Production |
Security Best Practices
# Non-root user
RUN addgroup -S app && adduser -S app -G app
USER app
# Read-only filesystem
# (Configure at runtime with --read-only)
# No shell access with distroless
FROM gcr.io/distroless/java21-debian12
# Health check
HEALTHCHECK --interval=30s --timeout=3s \
CMD wget -qO- localhost:8080/actuator/health || exit 1Troubleshooting
Common Issues
| Problem | Cause | Solution |
|---|---|---|
| OOMKilled | Heap > limit | Set MaxRAMPercentage |
| Slow startup | Large image | Multi-stage build |
| Permission denied | Root required | Fix file permissions |
| No memory info | Old JVM | Update to Java 11+ |
Debug Checklist
□ Check container memory limits
□ Verify JVM sees container limits
□ Review health check configuration
□ Scan image for vulnerabilities
□ Test with resource constraintsUsage
Skill("java-docker")Related Skills
java-maven-gradle- Build integrationjava-microservices- K8s deployment
# java-docker Configuration
# Category: containers
# Generated: 2025-12-30
skill:
name: java-docker
version: "1.0.0"
category: containers
settings:
# Default settings for java-docker
enabled: true
log_level: info
# Category-specific defaults
validation:
strict_mode: false
auto_fix: false
output:
format: markdown
include_examples: true
# Environment-specific overrides
environments:
development:
log_level: debug
validation:
strict_mode: false
production:
log_level: warn
validation:
strict_mode: true
# Integration settings
integrations:
# Enable/disable integrations
git: true
linter: true
formatter: true
FROM eclipse-temurin:21-jdk AS builder
WORKDIR /app
COPY . .
RUN ./mvnw package -DskipTests
FROM eclipse-temurin:21-jre
COPY --from=builder /app/target/*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]
{
"$schema": "http://json-schema.org/draft-07/schema#",
"title": "java-docker Configuration Schema",
"type": "object",
"properties": {
"skill": {
"type": "object",
"properties": {
"name": {
"type": "string"
},
"version": {
"type": "string",
"pattern": "^\\d+\\.\\d+\\.\\d+$"
},
"category": {
"type": "string",
"enum": [
"api",
"testing",
"devops",
"security",
"database",
"frontend",
"algorithms",
"machine-learning",
"cloud",
"containers",
"general"
]
}
},
"required": [
"name",
"version"
]
},
"settings": {
"type": "object",
"properties": {
"enabled": {
"type": "boolean",
"default": true
},
"log_level": {
"type": "string",
"enum": [
"debug",
"info",
"warn",
"error"
]
}
}
}
},
"required": [
"skill"
]
}Java Docker Guide
Overview
This guide provides comprehensive documentation for the java-docker skill in the custom-plugin-java plugin.
Category: Containers
Quick Start
Prerequisites
- Familiarity with containers concepts
- Development environment set up
- Plugin installed and configured
Basic Usage
# Invoke the skill
claude "java-docker - [your task description]"
# Example
claude "java-docker - analyze the current implementation"Core Concepts
Key Principles
1. Consistency - Follow established patterns 2. Clarity - Write readable, maintainable code 3. Quality - Validate before deployment
Best Practices
- Always validate input data
- Handle edge cases explicitly
- Document your decisions
- Write tests for critical paths
Common Tasks
Task 1: Basic Implementation
# Example implementation pattern
def implement_java_docker(input_data):
"""
Implement java-docker functionality.
Args:
input_data: Input to process
Returns:
Processed result
"""
# Validate input
if not input_data:
raise ValueError("Input required")
# Process
result = process(input_data)
# Return
return resultTask 2: Advanced Usage
For advanced scenarios, consider:
- Configuration customization via
assets/config.yaml - Validation using
scripts/validate.py - Integration with other skills
Troubleshooting
Common Issues
| Issue | Cause | Solution |
|---|---|---|
| Skill not found | Not installed | Run plugin sync |
| Validation fails | Invalid config | Check config.yaml |
| Unexpected output | Missing context | Provide more details |
Related Resources
- SKILL.md - Skill specification
- config.yaml - Configuration options
- validate.py - Validation script
---
Last updated: 2025-12-30
Java Docker Patterns
Design Patterns
Pattern 1: Input Validation
Always validate input before processing:
def validate_input(data):
if data is None:
raise ValueError("Data cannot be None")
if not isinstance(data, dict):
raise TypeError("Data must be a dictionary")
return TruePattern 2: Error Handling
Use consistent error handling:
try:
result = risky_operation()
except SpecificError as e:
logger.error(f"Operation failed: {e}")
handle_error(e)
except Exception as e:
logger.exception("Unexpected error")
raisePattern 3: Configuration Loading
Load and validate configuration:
import yaml
def load_config(config_path):
with open(config_path) as f:
config = yaml.safe_load(f)
validate_config(config)
return configAnti-Patterns to Avoid
❌ Don't: Swallow Exceptions
# BAD
try:
do_something()
except:
pass✅ Do: Handle Explicitly
# GOOD
try:
do_something()
except SpecificError as e:
logger.warning(f"Expected error: {e}")
return default_valueCategory-Specific Patterns: Containers
Recommended Approach
1. Start with the simplest implementation 2. Add complexity only when needed 3. Test each addition 4. Document decisions
Common Integration Points
- Configuration:
assets/config.yaml - Validation:
scripts/validate.py - Documentation:
references/GUIDE.md
---
Pattern library for java-docker skill
#!/usr/bin/env python3
"""
Validation script for java-docker skill.
Category: containers
"""
import os
import sys
import yaml
import json
from pathlib import Path
def validate_config(config_path: str) -> dict:
"""
Validate skill configuration file.
Args:
config_path: Path to config.yaml
Returns:
dict: Validation result with 'valid' and 'errors' keys
"""
errors = []
if not os.path.exists(config_path):
return {"valid": False, "errors": ["Config file not found"]}
try:
with open(config_path, 'r') as f:
config = yaml.safe_load(f)
except yaml.YAMLError as e:
return {"valid": False, "errors": [f"YAML parse error: {e}"]}
# Validate required fields
if 'skill' not in config:
errors.append("Missing 'skill' section")
else:
if 'name' not in config['skill']:
errors.append("Missing skill.name")
if 'version' not in config['skill']:
errors.append("Missing skill.version")
# Validate settings
if 'settings' in config:
settings = config['settings']
if 'log_level' in settings:
valid_levels = ['debug', 'info', 'warn', 'error']
if settings['log_level'] not in valid_levels:
errors.append(f"Invalid log_level: {settings['log_level']}")
return {
"valid": len(errors) == 0,
"errors": errors,
"config": config if not errors else None
}
def validate_skill_structure(skill_path: str) -> dict:
"""
Validate skill directory structure.
Args:
skill_path: Path to skill directory
Returns:
dict: Structure validation result
"""
required_dirs = ['assets', 'scripts', 'references']
required_files = ['SKILL.md']
errors = []
# Check required files
for file in required_files:
if not os.path.exists(os.path.join(skill_path, file)):
errors.append(f"Missing required file: {file}")
# Check required directories
for dir in required_dirs:
dir_path = os.path.join(skill_path, dir)
if not os.path.isdir(dir_path):
errors.append(f"Missing required directory: {dir}/")
else:
# Check for real content (not just .gitkeep)
files = [f for f in os.listdir(dir_path) if f != '.gitkeep']
if not files:
errors.append(f"Directory {dir}/ has no real content")
return {
"valid": len(errors) == 0,
"errors": errors,
"skill_name": os.path.basename(skill_path)
}
def main():
"""Main validation entry point."""
skill_path = Path(__file__).parent.parent
print(f"Validating java-docker skill...")
print(f"Path: {skill_path}")
# Validate structure
structure_result = validate_skill_structure(str(skill_path))
print(f"\nStructure validation: {'PASS' if structure_result['valid'] else 'FAIL'}")
if structure_result['errors']:
for error in structure_result['errors']:
print(f" - {error}")
# Validate config
config_path = skill_path / 'assets' / 'config.yaml'
if config_path.exists():
config_result = validate_config(str(config_path))
print(f"\nConfig validation: {'PASS' if config_result['valid'] else 'FAIL'}")
if config_result['errors']:
for error in config_result['errors']:
print(f" - {error}")
else:
print("\nConfig validation: SKIPPED (no config.yaml)")
# Summary
all_valid = structure_result['valid']
print(f"\n==================================================")
print(f"Overall: {'VALID' if all_valid else 'INVALID'}")
return 0 if all_valid else 1
if __name__ == "__main__":
sys.exit(main())