Getting Groovy with JHipster and Micronaut

GETTINGGROOVY
WITH MICRONAUT & JHIPSTER

Web and JVM developer with a decade of
experience
Husband of Dad of
OSS contributor
2GM Team Member at OCI
ABOUTME
ZACHARY KLEIN, SENIOR SOFTWARE ENGINEER
ZACHARY KLEIN - APACHECON @HOME - SEPTEMBER 30, 2020
💇 🙆 👸 👶🙋

AGENDA

WHATISMICRONAUT?
• A framework for microservice & serverless applications
• Leverages Ahead Of Time (AOT) for DI, AOP, and
configuration injection
• Reactive HTTP layer built on Netty
• Declarative HTTP Client
• “Natively Cloud Native”
• Accompanied by a suite of official and community-
contributed integrations and libraries

WHATCANYOUBUILDWITHMICRONAUT?
• Microservices
• Serverless Applications
• Message-Driven Applications with Kafka/Rabbit
• CLI Applications
• Android Applications
• Anything with static void main(String..args)

WHATMAKESMICRONAUTDIFFERENT?
• Ahead of Time (AOT) Compilation
• No Reflection, Runtime Proxies, or Dynamic Classloading
• Optimized for GraalVM (and standard JVM)
• Natively Reactive
• Capable of running in low-memory environments with sub
second startup time
• Polyglot: supports Java, Kotlin, and Groovy

WHATMAKESMICRONAUTDIFFERENT?
• Configurations oﬀered for…
• Cloud platforms (AWS, Google Cloud, Microsoft Azure)
• Messaging frameworks (Kafka, RabbitMQ, nats.io)
• Data access (MongoDB, Neo4j, Redis, SQL/JDBC, Cassandra
• Open API documentation (Swagger)
• Metrics libraries (Micrometer, rate limiting libraries)
• Server-side view rendering

MICRONAUTANDGROOVY
• First-class support for Groovy
• Controllers, filters, beans, factories, configuration
• @MicronautTest for Spock
• AST Transformations
• Static Compilation
• Interoperability

DEPENDENCYINJECTION&AOP
• Full Featured Dependency Injection (DI) Container
• JSR-330 Compliant
• Minimizes Runtime Reflection
• AOP APIs

Generated Bytecode resides in
the same package as your source
code - your code is never altered
by Micronaut

import javax.inject.Singleton
@Singleton
class MessageHelper {
String createMessage() { // … }
}
Mind the package!

import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import javax.inject.Inject
@Controller("/")
class HelloController {
@Inject
MessageHelper messageHelper
// ...
}

@Controller("/")
class HelloController {
MessageHelper messageHelper
public HelloController(MessageHelper messageHelper) {
this.messageHelper = messageHelper
}
// ...
}

CONFIGURATION
• Configuration formats: YML (default), Groovy, JSON, Java
Properties
• Environment detection and env-specific config
• Configuration injection via annotations or
@ConfigurationProperties
info.demo.string = "demo string"
info.demo.number = 123
info.demo.map = [key: 'value',
other_key: 123]
application.groovy

CONTROLLERS
package example
@Controller('/')
class GroovyHelloController {
@Get('/hello/{name}')
String hello(String name) {
"Hello $name From Groovy"
}
}

CLIENTS
package example
@Client(‘/') // or (id = ‘service-id’)
class GroovyHelloClient {
@Get('/hello/{name}')
String hello(String name)
}

MANAGEMENTENDPOINTS
• Provided by the micronaut-management library
• Similar conceptually to Actuator endpoints in Spring
Boot/Grails
• Endpoints can be defined as sensitive (requiring
authentication)
• Support GET, POST, and DELETE requests
• Can be exposed via JMX
• Custom endpoints supported

/beans Returns information about the loaded bean definitions in
the application
/info Returns static information from the state of the
application
/health Returns information about the "health" of the application
/metrics Return the application metrics. Requires the micrometer-
core configuration on the classpath
/refresh Refreshes bean state
/routes Returns information about URIs available to be called for
your application
/stop Shuts down the application server (disabled by default)
/loggers View and mutate logging configuration (e.g, POST to change
log levels at runtime)
/env Returns all currently resolved configuration properties
DEFAULT MANAGEMENT ENDPOINTS

MICRONAUT&GROOVY
• Groovy is a 1st class language in Micronaut!
• Applications can be generated with Groovy
as the default language (e.g, code-gen for
controllers, clients, Application class, etc)
• Groovy supported as configuration syntax
• Compile-time DI/AOP provided using Groovy
AST Transformations
• Groovy classes can also be used within Java
Micronaut apps (e.g, Spock tests, helper/util
classes)
❤

MICRONAUT&GROOVY
• Groovy can be used for:
• Controllers & Clients
• Filters
• All bean types
• AOP advice
• Configuration
• Serverless functions
❤

“ADEVELOPMENTPLATFORMTO
QUICKLYGENERATE,DEVELOP,&
DEPLOYMODERNWEBAPPLICATIONS
&MICROSERVICEARCHITECTURES.”
HTTPS://WWW.JHIPSTER.TECH

WHATISJHIPSTER?
• Project generator for modern JVM web apps
• Originally designed for Spring Boot and Angular
• Now supports React and Vue.js frontends, and Micronaut as a
backend via the Hipster blueprint
• Provides user admin UI, management UI, and “scaﬀolding” views for
database entities
• Oﬀers features to easily enable OAuth2 authentication
• JDL (JHipster Domain Language) can be used to define the domain
model (and project options) for your app

JHIPSTER&MICRONAUT
• Development sponsored by Object Computing, Inc
• Custom Blueprint supplies a Micronaut backend
• Still in active development!
• Features currently supported include:
• Maven (default) or Gradle
• MySQL, Postgres, H2
• JWT or OAuth 2.0 authentication
• Angular or React client app

CREATINGAJHIPSTERAPPLICATION
1. Install MHipster
◦ npm install -g generator-jhipster-micronaut
2. Create a new folder for your application
3. Start MHipster
◦ mhipster

JHIPSTER/MICRONAUT+GROOVY!
• JHipster projects use Java only by default, :( however…
• Groovy can be added to the project with fairly minimal build
configuration! :)
• Groovy can be used for project configuration (?)
• Micronaut’s joint-compilation support for Groovy allows
bidirectional DI within your app

DEMO!DEMO!DEMO!

WRAPUP
• Micronaut is a powerful, performant framework for JVM apps -
including Groovy!
• JHipster allows you to quickly bootstrap a full-featured
application with Micronaut with very little coding
• With a bit of custom config, you can take advantage of Groovy
and Micronaut’s support for the Groovy language within your
JHipster project
• Approach is applicable to any Micronaut project (not just
JHipster)
❤

QUESTIONS?

THANKYOU
ZACHARY KLEIN
SENIOR SOFTWARE ENGINEER
GRAILS & MICRONAUT CORE TEAM MEMBER
KLEINZ@OBJECTCOMPUTING.COM
@ZACHARYAKLEIN
https://micronaut.io
https://objectcomputing.com/resources/events
SAMPLE CODE: HTTPS://GITHUB.COM/ZACHARYKLEIN/GROOVY-JHIPSTER

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