spring-cloud-function/aws-intro.html

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<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#_notes_on_jar_layout">Notes on JAR Layout</a></li>
<li><a href="#_upload">Upload</a></li>
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<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>The adapter has a couple of generic request handlers that you can use. The most generic is <code>SpringBootStreamHandler</code>, which uses a Jackson <code>ObjectMapper</code> provided by Spring Boot to serialize and deserialize the objects in the function. There is also a <code>SpringBootRequestHandler</code> 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).</p>
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<div class="paragraph">
<p>If your app has more than one <code>@Bean</code> of type <code>Function</code> etc. then you can choose the one to use by configuring <code>function.name</code> (e.g. as <code>FUNCTION_NAME</code> environment variable in AWS). The functions are extracted from the Spring Cloud <code>FunctionCatalog</code> (searching first for <code>Function</code> then <code>Consumer</code> and finally <code>Supplier</code>).</p>
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<div class="sect1">
<h2 id="_notes_on_jar_layout"><a class="link" href="#_notes_on_jar_layout">Notes on JAR Layout</a></h2>
<div class="sectionbody">
<div class="paragraph">
<p>You don&#8217;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 <code>aws</code> classifier for deploying in Lambda, and one executable (thin) jar that includes <code>spring-cloud-function-web</code> at runtime. Spring Cloud Function will try and locate a "main class" for you from the JAR file manifest, using the <code>Start-Class</code> attribute (which will be added for you by the Spring Boot tooling if you use the starter parent). If there is no <code>Start-Class</code> in your manifest you can use an environment variable <code>MAIN_CLASS</code> when you deploy the function to AWS.</p>
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<div class="sect1">
<h2 id="_upload"><a class="link" href="#_upload">Upload</a></h2>
<div class="sectionbody">
<div class="paragraph">
<p>Build the sample under <code>spring-cloud-function-samples/function-sample-aws</code> and upload the <code>-aws</code> jar file to Lambda. The handler can be <code>example.Handler</code> or <code>org.springframework.cloud.function.adapter.aws.SpringBootStreamHandler</code> (FQN of the class, <em>not</em> a method reference, although Lambda does accept method references).</p>
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<div class="listingblock">
<div class="content">
<pre>./mvnw -U clean package</pre>
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<div class="paragraph">
<p>Using the AWS command line tools it looks like this:</p>
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<div class="listingblock">
<div class="content">
<pre>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</pre>
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<div class="paragraph">
<p>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:</p>
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<div class="listingblock">
<div class="content">
<pre>{
  "value": "test"
}</pre>
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<div class="admonitionblock note">
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<td class="icon">
<i class="fa icon-note" title="Note"></i>
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<td class="content">
The AWS sample app is written in the "functional" style (as an <code>ApplicationContextInitializer</code>). This is much faster on startup in Lambda than the traditional <code>@Bean</code> style, so if you don&#8217;t need <code>@Beans</code> (or <code>@EnableAutoConfiguration</code>) it&#8217;s a good choice. Warm starts are not affected.
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