Unlike applications congenital appliance acceptable JVM frameworks, Micronaut has 100% compile-time, reﬂection free, annex bang and AOP. Thus, Micronaut applications are baby and accept a low anamnesis footprint. With Micronaut, you can advance a big brace or a baby action which can be deployed AWS Lambda. You are not accountable by the framework.
Micronaut additionally integrates billow technologies into the framework, and microservice patterns such as account discovery, broadcast tracing, ambit breaker are broiled into the framework.
Micronaut was appear as open-source in May 2018, and is appointed to absolution its 1.0.0 adaptation by the end of 2018. You can try Micronaut today, as ceremony and absolution applicant versions are available.
Micronaut development aggregation is the aforementioned accumulation behind Grails Framework. Grails, who afresh accomplished its 10th year anniversary, continues to advice developers to ability web applications with abounding abundance boosters. Grails 3 is congenital on top of Spring Boot. As you will anon discover, Micronaut has an accessible acquirements ambit for developers advancing from both frameworks, Grails and Spring Boot.
In this alternation of articles, we are activity to actualize an appliance composed by several microservices:
The aing diagram illustrates the app, you will build:
The easiest way to actualize Micronaut apps is to use its command band interface (Micronaut CLI) which can be installed via calmly With SDKMan.
Micronaut applications can be accounting in Java, Kotlin and Groovy. Let us actualize a Adequate Micronaut app ﬁrst:
mn create-app example.micronaut.books –lang adequate .
The antecedent command creates an app named books with a absence amalgamation of example.micronaut.
Micronaut is analysis framework-agnostic. It selects a absence testing framework based on the accent you use. By absence for Java, JUnit is used. If you baddest Groovy, by default, Spock is used. You can mix altered languages and testing frameworks. For example, a Java micronaut app activated with Spock.
Moreover, Micronaut is body apparatus agnostic. You can use Maven or Gradle. By default, Gradle will be used.
The generated app includes a non-blocking HTTP server based on Netty.
Create a ambassador to betrayal your ﬁrst Micronaut endpoint:
Several things are account acknowledgment in the antecedent code.
The antecedent ambassador uses an interface and a POGO:
Micronaut affairs up at abridge time a bean implementing the BooksRepository interface.
For this app, we actualize a singleton, which we deﬁne with the javax.inject.Singleton annotation.
Functional tests add the best amount back they analysis the appliance in its entirety. However, with added frameworks, anatomic and affiliation tests are hardly used. Mostly, because back they absorb the alpha of the accomplished application, they are slow.
However, autograph anatomic tests in Micronaut is a joy. Because they are fast; absolutely fast.
A anatomic analysis for the antecedent ambassador is listed below:
Several things are account advertence from the antecedent test:
Run the aing command to actualize addition microservice called account . This time, we use Kotlin as the language.
mn create-app example.micronaut.inventory –lang kotlin
This new microservice controls the banal of anniversary book.
Create a Kotlin Data Class to abbreviate the domain:
Create a Ambassador which allotment a book’s stock.
Create a Java aperture app which consumes both books and inventory microservices.
mn create-app example.micronaut.gateway
Java is best by absence if you do not specify the lang ﬂag.
Inside the aperture microservice, actualize one declarative HTTP Client to acquaint with the books microservice.
First actualize an interface:
Then actualize a allegorical HTTP Client; an interface annotated with @Client.
Micronaut allegorical HTTP Applicant methods will be implemented for you at abridge time, abundantly simplifying the conception of HTTP clients.
Also, Micronaut supports the abstraction of application environment. In the antecedent cipher listing, you can see how accessible is to attenuate the loading of some beans for a accurate ambiance with @Requires annotation.
Moreover, as you can see from the antecedent cipher sample non blocking types are ﬁrst chic citizens in Micronaut. The BooksClient::fetchBooks() adjustment returns Flowable<Book> where Book is a Java POJO:
Create addition allegorical HTTP Applicant to acquaint with the inventory microservice.
First actualize an interface:
Then, an HTTP allegorical client:
Now, actualize a ambassador which injects both beans and creates a acknowledging response.
Before we can actualize a anatomic analysis for the controller, we charge to actualize bean implementations for ( BooksFetcher and InventoryFetcher) at the analysis environment.
Create a bean which conforms to BooksFetcher interface, alone accessible for the analysis environment; see @Requires annotation.
Create a bean which conforms to InventoryFetcher interface, alone accessible for the analysis environment.
Create a anatomic test. In the Adequate microservice we wrote a Spock test, this time we address JUnit analysis instead.
We are activity to conﬁgure our micronaut microservice to annals with Consul Service discovery.
Consul is a broadcast account cobweb to connect, secure, and conﬁgure casework beyond any runtime belvedere and accessible or clandestine cloud
Integrating Micronaut and Delegate is simple.
First add to every microservice books, inventory and gateway the discovery-client dependency:
We charge to do some conﬁguration changes to anniversary app so that back the appliance starts, it registers with Consul.
Each account use the property micronaut.application.name as a account id back they annals in Consul. That it is why we use those exact names in the previous @Client annotation.
The antecedent cipher listings allegorize addition affection of Micronaut, ambiance capricious departure with absence ethics in conﬁguration ﬁles. See:
Also, in Micronaut you can accept ambiance speciﬁc conﬁguration ﬁles. We are activity to actualize a ﬁle named application-test.yml in anniversary of the environments to delegate allotment in the analysis phase.
The easiest way to alpha appliance Delegate is via Docker. Now, run a Docker instance.
docker run -p 8500:8500 consul
Create a multi-project build with Gradle. Actualize a settings.gradle book in the basis folder:
Now you can run anniversary app in parallel. Gradle has a accessible ﬂag ( -parallel ) for that:
./gradlew -parallel run
Each microservice starts in the conﬁgured ports: 8080, 8081 and 8082.
Consul comes with a HTML UI. Open http://localhost:8500/ui in your browser you will see:
Each Micronaut micro account has registered with delegate .
You can adjure the aperture microservice with the aing cURL command:
Congratulations you accept created your ﬁrst Micronaut arrangement of microservices!
During this tutorial you accept created three microservices with altered languages: Java, Kotlin and Groovy. You accept additionally abstruse how accessible it is to absorb added microservices with the Micronaut HTTP Client, and how to actualize anatomic tests that run fast. Moreover, you created aggregate adequate abounding reﬂection-free Annex Bang and AOP.
Join me for allotment two of the series, advancing soon. In the meantime, amuse feel chargeless to ask questions via the comments area below.
Sergio del Amo Caballero is a developer specialized in the development of adaptable buzz apps ( iOS, Android) powered by Grails / Micronaut backends. Back 2015, Sergio del Amo writes a newsletter, Adequate Calamari, about the Adequate Ecosystem and Microservices. Groovy, Grails, Micronaut, Gradle,…
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