java-tutorials/microservices-modules/lagom

Lagom

This module contains articles about the Lagom framework.

Relevant articles

• Guide to Reactive Microservices Using Lagom Framework

Steps to setup from scratch

1. Create sbt build file "build.sbt"

2. Create plugins file project/plugins.sbt

3. Create build properties file project/build.properties

4. Run sbt command from project root to generate project directories, generated projects at target/lagom-dynamic-projects Service Locator project: lagom-internal-meta-project-service-locator cassandra project: lagom-internal-meta-project-cassandra

5. Create folders in all projects to follow maven like directory structure layout for project source code: src/main/java and src/main/java/resources and test folders.

6. Weather microservice a) WeatherService Interface with method: weatherStatsForToday() b) WeatherServiceImpl to return weatherstats from a random list of weather stats

7. Greeting Microservice GreetingService Interface: handleGreetFrom(String user)

   a) Reply back to user with greeting message("Hello") along with weather stats fetched from weather microservice b) Update the greeting message("Hello Again") for an existing user.

8. GreetingEntity: PersistentEntity<GreetingCommand, GreetingEvent, GreetingState> a) handles ReceivedGreetingCommand b) Stores ReceivedGreetingEvent events to cassandra c) Processes ReceivedGreetingEvent to update GreetingState("Hello" to "Hello Again") if required.

9. Register modules with lagom using application.conf files.

10. Run project: sbt lagom:runAll

Sample Run:

$ curl http://localhost:9000/api/greeting/Nikhil;
Hello Nikhil! Today's weather stats: Going to be very humid, Take Water

$ curl http://localhost:9000/api/greeting/Nikhil;
Hello Again Nikhil! Today's weather stats: Going to Rain, Take Umbrella