spring-cloud-function/intro.html

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<body class="book">
<div id="header">
</div>
<div id="content">
<div id="preamble">
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<div class="paragraph">
<p>Spring Cloud Function is a project with the following high-level goals:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Promote the implementation of business logic via functions.</p>
</li>
<li>
<p>Decouple the development lifecycle of business logic from any specific runtime target so that the same code can run as a web endpoint, a stream processor, or a task.</p>
</li>
<li>
<p>Support a uniform programming model across serverless providers, as well as the ability to run standalone (locally or in a PaaS).</p>
</li>
<li>
<p>Enable Spring Boot features (auto-configuration, dependency injection, metrics) on serverless providers.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>It abstracts away all of the transport details and
infrastructure, allowing the developer to keep all the familiar tools
and processes, and focus firmly on business logic.</p>
</div>
<div class="paragraph">
<p>Here&#8217;s a complete, executable, testable Spring Boot application
(implementing a simple string manipulation):</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootApplication
public class Application {

  @Bean
  public Function&lt;Flux&lt;String&gt;, Flux&lt;String&gt;&gt; uppercase() {
    return flux -&gt; flux.map(value -&gt; value.toUpperCase());
  }

  public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
  }
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>It&#8217;s just a Spring Boot application, so it can be built, run and
tested, locally and in a CI build, the same way as any other Spring
Boot application. The <code>Function</code> is from <code>java.util</code> and <code>Flux</code> is a
<a href="https://www.reactive-streams.org/">Reactive Streams</a> <code>Publisher</code> from
<a href="https://projectreactor.io/">Project Reactor</a>. The function can be
accessed over HTTP or messaging.</p>
</div>
<div class="paragraph">
<p>Spring Cloud Function has 4 main features:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Wrappers for <code>@Beans</code> of type <code>Function</code>, <code>Consumer</code> and
<code>Supplier</code>, exposing them to the outside world as either HTTP
endpoints and/or message stream listeners/publishers with RabbitMQ, Kafka etc.</p>
</li>
<li>
<p>Compiling strings which are Java function bodies into bytecode, and
then turning them into <code>@Beans</code> that can be wrapped as above.</p>
</li>
<li>
<p>Deploying a JAR file containing such an application context with an
isolated classloader, so that you can pack them together in a single
JVM.</p>
</li>
<li>
<p>Adapters for <a href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-aws">AWS Lambda</a>, <a href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-azure">Azure</a>, <a href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-openwhisk">Apache OpenWhisk</a> and possibly other "serverless" service providers.</p>
</li>
</ol>
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