Ninja can easily be extended by modules. This page contains popular modules available for Ninja. Usually the linked pages contain a short description how to setup stuff:
Google AppEngine Support
Undertow standalone - alternative to Jetty
Rythm templates
Mustache templates
Jade4Ninja (Jade) templates
Rocker templates
Pebble templates
EBean RDBMS ORM support (for EBean versions <= 7.2.3)
EBean RDBMS ORM support (for EBean versions > 7.2.3)
MongoDB/Morphia Integration
Cassandra
Auth0 (authentication SaaS) integration
Activity support - light-weight workflow and Business Process Management (BPM)
Camunda BPMN Integration - Camunda Workflow, Business Process, and Decision Management
Executors and critical long lived tasks
Prometheus (metrics and exporter)
Redis (cache and pooling)
RabbitMQ (pooling and sessions)
Hazelcast Cache Implementation
Quartz Scheduler Integration
Sitemap Generator