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This project provides an adapter layer for a Spring Cloud Function application onto AWS Lambda. You can write an app with a single `@Bean` of type `Function`, `Consumer` or `Supplier` and it will be deployable in AWS if you get the JAR file laid out right. The best way to make it work is to include `spring-cloud-function-context` as a dependency, but not the higher level adapters (e.g. `spring-cloud-function-stream`).
The adapter has a couple of generic request handlers that you can use. The most generic is `SpringBootStreamHandler`, which uses a Jackson `ObjectMapper` provided by Spring Boot to serialize and deserialize the objects in the function. There is also a `SpringBootRequestHandler` which you can extend, and provide the input and output types as type parameters (enabling AWS to inspect the class and do the JSON conversions itself).
If your app has more than one `@Bean` of type `Function` etc. then you can choose the one to use by configuring `function.name` (e.g. as `FUNCTION_NAME` environment variable in AWS). The functions are extracted from the Spring Cloud `FunctionCatalog` (searching first for `Function` then `Consumer` and finally `Supplier`).
== Notes on JAR Layout
You don't need the Spring Cloud Function Web or Stream adapter at runtime in Lambda, so you might need to exclude those before you create the JAR you send to AWS. A Lambda application has to be shaded, but a Spring Boot standalone application does not, so you can run the same app using 2 separate jars (as per the sample). The sample app creates 2 jar files, one with an `aws` classifier for deploying in Lambda, and one executable (thin) jar that includes `spring-cloud-function-web` at runtime. Spring Cloud Function will try and locate a "main class" for you from the JAR file manifest, using the `Start-Class` attribute (which will be added for you by the Spring Boot tooling if you use the starter parent). If there is no `Start-Class` in your manifest you can use an environment variable `MAIN_CLASS` when you deploy the function to AWS.
== Upload
Build the sample under `spring-cloud-function-samples/function-sample-aws` and upload the `-aws` jar file to Lambda. The handler can be `example.Handler` or `org.springframework.cloud.function.adapter.aws.SpringBootStreamHandler` (FQN of the class, _not_ a method reference, although Lambda does accept method references).
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./mvnw -U clean package
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Using the AWS command line tools it looks like this:
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aws lambda create-function --function-name Uppercase --role arn:aws:iam::[USERID]:role/service-role/[ROLE] --zip-file fileb://function-sample-aws/target/function-sample-aws-2.0.0.BUILD-SNAPSHOT-aws.jar --handler org.springframework.cloud.function.adapter.aws.SpringBootStreamHandler --description "Spring Cloud Function Adapter Example" --runtime java8 --region us-east-1 --timeout 30 --memory-size 1024 --publish
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The input type for the function in the AWS sample is a Foo with a single property called "value". So you would need this to test it:
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{
"value": "test"
}
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NOTE: The AWS sample app is written in the "functional" style (as an `ApplicationContextInitializer`). This is much faster on startup in Lambda than the traditional `@Bean` style, so if you don't need `@Beans` (or `@EnableAutoConfiguration`) it's a good choice. Warm starts are not affected.
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