Framework Micronaut - datastaxdevs/awesome-astra GitHub Wiki

🏠 Back to home | Written by Cedrick Lunven, Last Update 2/10/2021

This guide was built base on the Micronaut Cassandra Guide

📋 On this page

A - Overview
B - Prerequisites
C - Configuration over CQL with Datastax Drivers

A - Overview

Micronaut is a modern, JVM-based, full stack Java framework designed for building modular, easily testable JVM applications with support for Java, Kotlin, and Groovy. Micronaut is developed by the creators of the Grails framework and takes inspiration from lessons learnt over the years building real-world applications from monoliths to microservices using Spring, Spring Boot and Grails. For more information refer to the user guide

The micronaut-cassandra module includes support for integrating Micronaut services with Cassandra.

B - Prerequisites

You should have an Astra account
You should Create and Astra Database
You should Have an Astra Token
You should Download your Secure bundle
You should install a Java JDK 1.8+ and Apache Maven

C - Configuration

You can find a working sample here

✅ Step 1: Create your project

To create a micronaut project and CLI mn is provided. You can install it using sdkman as describe in the doc

#Download SDKMan
curl -s https://get.sdkman.io | bash

#Setup SDKMan
source "$HOME/.sdkman/bin/sdkman-init.sh"

#Download Micronaut
sdk install micronaut

To generate a new project use mn create-app adding the feature cassandra

mn create-app astra-todo-micronaut --features cassandra

Notice that in your pom.xml you now have the following

<dependency>
   <groupId>io.micronaut.cassandra</groupId>
   <artifactId>micronaut-cassandra</artifactId>
   <scope>compile</scope>
</dependency>

✅ Step 2: Setup your project

All configuration of your project will be defined in application.yaml in src/main/resources. The module is clever enough to load all properties as if it was the driver configuration file.

You can defined multiple profiles and each profile will be identified with key cassandra.${profile_name}. There is a default profile. In the following sample file we provide 2 profiles one for local and one for Astra. There is no extra code needed, simply configuration.

cassandra:
  default:
    basic:
      session-keyspace: micronaut
      contact-points:
        - "localhost:9042"
      load-balancing-policy:
        local-datacenter: datacenter1
  astra:
    basic:
      request:
        timeout: 5 seconds
        consistency: LOCAL_QUORUM
        page-size: 5000
      session-keyspace: micronaut
      cloud:
        secure-connect-bundle: /Users/cedricklunven/Downloads/secure-connect-workshops.zip
    advanced:
      auth-provider:
        class: PlainTextAuthProvider
        username: token
        password: "AstraCS:blahblahblah"
      connection:
        init-query-timeout: 10 seconds          
        set-keyspace-timeout: 10 seconds
      control-connection.timeout: 10 seconds

✅ Step 3: Application Startup

At startup you may want create the different tables needed for you application. In Astra you can only create keyspaces from the devops API or the user interface..

To enable content at startup simple implement ApplicationEventListener<ServiceReadyEvent> as shown below

@Singleton
public class TodoApplicationStartup  implements ApplicationEventListener<ServiceReadyEvent> {

    /** Logger for the class. */
    private static final Logger LOGGER = LoggerFactory.getLogger(TodoApplicationStartup.class);
    
    @Property(name = "todo.cassandra.create_schema", defaultValue="false")
    private boolean createTable;
    
    @Inject 
    private CqlSession cqlSession;
    
    /** {@inheritDoc} */
    @Override
    public void onApplicationEvent(final ServiceReadyEvent event) {
        LOGGER.info("Startup Initialization");
        if (createTable) {
            TodoServiceCassandraCql.createTableTodo(cqlSession);
            LOGGER.info("+ Table TodoItems created if needed.");
        }
        LOGGER.info("[OK]");
    }
}

✅ Step 4: Use Cassandra

To use Cassandra you will reuse the CqlSession from the Datastax drivers. You can simply inject it where you needed as shown in this sample code

@Validated
@Controller("/api/v1")
public class TodoRestController {
    
    /** Logger for our Client. */
    private static final Logger LOGGER = LoggerFactory.getLogger(TodoRestController.class);
    
    /** CqlSession initialized from application.yaml */
    @Inject
    private CqlSession cqlSession;

Happy coding.