Quick start Spring

You can use the aws-serverless-java-container library to run a Spring application in AWS Lambda. You can use the library within your Lambda handler to load your Spring application and proxy events to it.

In the repository we have included a sample Spring application to get you started.

Maven archetype

You can quickly create a new serverless Spring application using our Maven archetype. First, make sure Maven is installed in your environment and available in your PATH. Next, using a terminal or your favorite IDE create a new application, the archetype groupId is com.amazonaws.serverless.archetypes and the artifactId is aws-serverless-spring-archetype;

mvn archetype:generate -DgroupId=my.service -DartifactId=my-service -Dversion=1.0-SNAPSHOT \
       -DarchetypeGroupId=com.amazonaws.serverless.archetypes \ 
       -DarchetypeArtifactId=aws-serverless-spring-archetype \
       -DarchetypeVersion=1.0.2 

The archetype sets up a new maven project. The pom.xml includes the dependencies you will need to build a basic Spring API. The generated code includes a StreamLambdaHandler class, the main entry point for AWS Lambda; a SpringApiConfig class that defines a basic Spring application; a controller package with a /ping resource; and a set of unit tests that exercise the application.

The project also includes a file called sam.yaml. This is a SAM template that you can use to quickly test your application in local or deploy it to AWS. Open the README.md file in the project root folder for instructions on how to use SAM Local to run your Serverless API or deploy it to AWS.

Manual setup / Converting existing projects

1. Import dependencies

The first step is to import the Spring implementation of the library:

<dependency>
    <groupId>com.amazonaws.serverless</groupId>
    <artifactId>aws-serverless-java-container-spring</artifactId>
    <version>[0.8,)</version>
</dependency>

This will automatically also import the aws-serverless-java-container-core and aws-lambda-java-core libraries.

Dependency injection with Spring can have a significant impact on your function's cold start time. To address this, you can include the spring-context-indexer dependency to generate a list of candidate components at compile time.

2. Create the Lambda handler

In your application package declare a new class that implements Lambda's RequestStreamHandler interface. If you have configured API Gateway with a proxy integration, you can use the built-in POJOs AwsProxyRequest and AwsProxyResponse.

The next step is to declare the container handler object. The library exposes a utility static method that configures a SpringLambdaContainerHandler object for AWS proxy events. The method receives a class annotated with Spring's @Configuration that defines your application. The object should be declared as a class property and be static. By doing this, Lambda will re-use the instance for subsequent requests.

The handleRequest method of the class can use the handler object we declared in the previous step to send requests to the Spring application.

public class StreamLambdaHandler implements RequestStreamHandler {
    private static SpringLambdaContainerHandler<AwsProxyRequest, AwsProxyResponse> handler;
    static {
        try {
            handler = SpringLambdaContainerHandler.getAwsProxyHandler(PetStoreSpringAppConfig.class);
        } catch (ContainerInitializationException e) {
            // if we fail here. We re-throw the exception to force another cold start
            e.printStackTrace();
            throw new RuntimeException("Could not initialize Spring framework", e);
        }
    }

    @Override
    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context)
            throws IOException {
        handler.proxyStream(inputStream, outputStream, context);

        // just in case it wasn't closed by the mapper
        outputStream.close();
    }
}

In our sample application The PetStoreSpringAppConfig class contains the configuration.

@Configuration
@ComponentScan("com.amazonaws.serverless.sample.spring")
public class PetStoreSpringAppConfig {
}

3. Publish your Lambda function

You can follow the instructions in AWS Lambda's documentation on how to package your function for deployment.

Spring profiles

You can enable Spring Profiles (as defined with the @Profile annotation) by using the SpringLambdaContainerHandler.activateSpringProfiles(String...) method - common drivers of this might be the AWS Lambda stage that you're deployed under, or stage variables. See @Profile documentation for details.