A Simple Localstack and Spring Integration

About Localstack

LocalStack is a fully functional local AWS cloud stack. It provides an easy-to-use test/mocking framework for developing Cloud applications. Currently, the focus is primarily on supporting the AWS cloud stack.

You can checkout more about here.

Distribution

This library is distributed under Apache 2.0 license and it is available as an artifact in Maven Central. You can just simply add the following dependency to your project.

Maven:

<dependency>
	<groupId>xyz.fabiano</groupId>  
	<artifactId>spring-localstack</artifactId>  
	<version>0.0.7</version>
</dependency>

Gradle:

compile 'xyz.fabiano:spring-localstack:0.0.7'

Requirements

Before you get up and running, you must meet the following requirements:

• Java (1.8 or greater)
• Spring (Starting from 4.x)
• Docker (service running)

Spring Boot Configuration

To activate the auto-configuration with Spring Boot, just add the following property:

spring.localstack.enabled=true  

When you get your application running, this property will get up a docker image with Localstack and instantiate beans for each AWS client already with the needed configuration for use them with Localstack. Then, you can just inject them like this:

@Component
public class MyComponent {
	@Autowired  
	private AmazonS3 amazonS3;

	...
	
	public uploadFileToS3(File file) {
		PutObjectRequest request = new PutObjectRequest("my-bucket", "my-data", file);  
		amazonS3.putObject(request);
	}
}

Below, you can check it out all available configuration options for this library:

##
#   Enables Localstack auto-configuration and runs it when getting Spring up.
#   The auto-configuration already creates all the AWS clients with the endpoint configuration,
#   so you do not need to instantiate or configure then, just inject it.
##
spring.localstack.enabled=true

##
#   Enables Async clients and creates it in the Spring Context
##
spring.localstack.async-clients.enabled=true

##
#   This tells the application for always look for a new Docker image if available.
##
spring.localstack.pull-new-image=true

##
#   With this option you can specify which services you want to run with Localstack.
#   This makes the Localstack container more lightweight.
##
spring.localstack.services=sqs,sns

##
#   Enable randoms ports for the Localstack container. It's a nice option to avoid port conflicts.
#   If you use the client beans, you do not need to worry about the endpoints and ports,
#   it will already configured with the random ports.
##
spring.localstack.random-ports=true

##
#   You can specify which is the Docker host for the container to use.
##
spring.localstack.external-host=localhost

##
#   You can specify is container will be removed after stop. Default: true
##
spring.localstack.auto-remove=false

##
#   You can specify the extra-options for the container.
##
spring.localstack.extra-options=

##
#   You can specify which is the region. Default: us-east-1
##
spring.localstack.region=sa-east-1

Testing with JUnit Runner

Warning: This option is for testing and you should use it when you do NOT have Localstack integrated with Springboot. if you are using Springboot integrated with Localstack you should use the SpringRunner.class.

This option will fit you if you wish to get Spring Context and the Localstack container at the same time for this particular test. The class SpringLocalstackDockerRunner is a JUnit runner with the purpose of testing integrated with Localstack and Spring. With this runner, we can compound with @SpringLocalstackProperties for more extensible configuration. Check it out:

@RunWith(SpringLocalstackDockerRunner.class)
@SpringLocalstackProperties(services = { S3 })
@ContextConfiguration(classes = SpringTestContext.class)
public class SpringWithLocalstackExampleTest {
	@Autowired
	private AmazonS3 amazonS3;

	@Test
	public void testIfHas10Files() {
	    ...
	    
	    ObjectListing listing = amazonS3.listObjects("my-bucket", "a-preffix");
	    assertThat(listing.getObjectSummaries().size(), is(10));
	}
}

And the context configuration:

@Configuration
public class SpringTestContext {

    @Bean
    public AmazonDockerClientsHolder amazonDockerClientsHolder() {
        return new AmazonDockerClientsHolder(LocalstackDocker.getLocalstackDocker());
    }

    @Bean
    public AmazonS3 amazonS3(AmazonDockerClientsHolder amazonDockerClientsHolder) {
        return amazonDockerClientsHolder.amazonS3();
    }
}