422 lines
15 KiB
HTML
422 lines
15 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="en">
|
|
<head>
|
|
<meta charset="UTF-8">
|
|
<!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]-->
|
|
<meta name="viewport" content="width=device-width, initial-scale=1.0">
|
|
<meta name="generator" content="Asciidoctor 1.5.8">
|
|
<title>Comparing Functional with Traditional Bean Definitions</title>
|
|
<link rel="stylesheet" href="css/spring.css">
|
|
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
|
|
|
|
<style>
|
|
.hidden {
|
|
display: none;
|
|
}
|
|
|
|
.switch {
|
|
border-width: 1px 1px 0 1px;
|
|
border-style: solid;
|
|
border-color: #7a2518;
|
|
display: inline-block;
|
|
}
|
|
|
|
.switch--item {
|
|
padding: 10px;
|
|
background-color: #ffffff;
|
|
color: #7a2518;
|
|
display: inline-block;
|
|
cursor: pointer;
|
|
}
|
|
|
|
.switch--item:not(:first-child) {
|
|
border-width: 0 0 0 1px;
|
|
border-style: solid;
|
|
border-color: #7a2518;
|
|
}
|
|
|
|
.switch--item.selected {
|
|
background-color: #7a2519;
|
|
color: #ffffff;
|
|
}
|
|
</style>
|
|
<script src="https://cdnjs.cloudflare.com/ajax/libs/zepto/1.2.0/zepto.min.js"></script>
|
|
<script type="text/javascript">
|
|
function addBlockSwitches() {
|
|
$('.primary').each(function() {
|
|
primary = $(this);
|
|
createSwitchItem(primary, createBlockSwitch(primary)).item.addClass("selected");
|
|
primary.children('.title').remove();
|
|
});
|
|
$('.secondary').each(function(idx, node) {
|
|
secondary = $(node);
|
|
primary = findPrimary(secondary);
|
|
switchItem = createSwitchItem(secondary, primary.children('.switch'));
|
|
switchItem.content.addClass('hidden');
|
|
findPrimary(secondary).append(switchItem.content);
|
|
secondary.remove();
|
|
});
|
|
}
|
|
|
|
function createBlockSwitch(primary) {
|
|
blockSwitch = $('<div class="switch"></div>');
|
|
primary.prepend(blockSwitch);
|
|
return blockSwitch;
|
|
}
|
|
|
|
function findPrimary(secondary) {
|
|
candidate = secondary.prev();
|
|
while (!candidate.is('.primary')) {
|
|
candidate = candidate.prev();
|
|
}
|
|
return candidate;
|
|
}
|
|
|
|
function createSwitchItem(block, blockSwitch) {
|
|
blockName = block.children('.title').text();
|
|
content = block.children('.content').first().append(block.next('.colist'));
|
|
item = $('<div class="switch--item">' + blockName + '</div>');
|
|
item.on('click', '', content, function(e) {
|
|
$(this).addClass('selected');
|
|
$(this).siblings().removeClass('selected');
|
|
e.data.siblings('.content').addClass('hidden');
|
|
e.data.removeClass('hidden');
|
|
});
|
|
blockSwitch.append(item);
|
|
return {'item': item, 'content': content};
|
|
}
|
|
|
|
function globalSwitch() {
|
|
$('.switch--item').each(function() {
|
|
$(this).off('click');
|
|
$(this).on('click', function() {
|
|
selectedText = $(this).text()
|
|
selectedIndex = $(this).index()
|
|
$(".switch--item").filter(function() { return ($(this).text() === selectedText) }).each(function() {
|
|
$(this).addClass('selected');
|
|
$(this).siblings().removeClass('selected');
|
|
selectedContent = $(this).parent().siblings(".content").eq(selectedIndex)
|
|
selectedContent.removeClass('hidden');
|
|
selectedContent.siblings().addClass('hidden');
|
|
});
|
|
});
|
|
});
|
|
}
|
|
|
|
$(addBlockSwitches);
|
|
$(globalSwitch);
|
|
|
|
</script>
|
|
|
|
</head>
|
|
<body class="book toc2 toc-left">
|
|
<div id="header">
|
|
<div id="toc" class="toc2">
|
|
<div id="toctitle">Table of Contents</div>
|
|
<ul class="sectlevel1">
|
|
<li><a href="#_comparing_functional_with_traditional_bean_definitions">Comparing Functional with Traditional Bean Definitions</a></li>
|
|
<li><a href="#_limitations_of_functional_bean_declaration">Limitations of Functional Bean Declaration</a></li>
|
|
<li><a href="#_testing_functional_applications">Testing Functional Applications</a></li>
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
<div id="content">
|
|
<div id="preamble">
|
|
<div class="sectionbody">
|
|
<div class="paragraph">
|
|
<p>Spring Cloud Function supports a "functional" style of bean declarations for small apps where you need fast startup. The functional style of bean declaration was a feature of Spring Framework 5.0 with significant enhancements in 5.1.</p>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_comparing_functional_with_traditional_bean_definitions"><a class="link" href="#_comparing_functional_with_traditional_bean_definitions">Comparing Functional with Traditional Bean Definitions</a></h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph">
|
|
<p>Here’s a vanilla Spring Cloud Function application from with the
|
|
familiar <code>@Configuration</code> and <code>@Bean</code> declaration style:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootApplication
|
|
public class DemoApplication {
|
|
|
|
@Bean
|
|
public Function<String, String> uppercase() {
|
|
return value -> value.toUpperCase();
|
|
}
|
|
|
|
public static void main(String[] args) {
|
|
SpringApplication.run(DemoApplication.class, args);
|
|
}
|
|
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>Now for the functional beans: the user application code can be recast into "functional"
|
|
form, like this:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootConfiguration
|
|
public class DemoApplication implements ApplicationContextInitializer<GenericApplicationContext> {
|
|
|
|
public static void main(String[] args) {
|
|
FunctionalSpringApplication.run(DemoApplication.class, args);
|
|
}
|
|
|
|
public Function<String, String> uppercase() {
|
|
return value -> value.toUpperCase();
|
|
}
|
|
|
|
@Override
|
|
public void initialize(GenericApplicationContext context) {
|
|
context.registerBean("demo", FunctionRegistration.class,
|
|
() -> new FunctionRegistration<>(uppercase())
|
|
.type(FunctionType.from(String.class).to(String.class)));
|
|
}
|
|
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>The main differences are:</p>
|
|
</div>
|
|
<div class="ulist">
|
|
<ul>
|
|
<li>
|
|
<p>The main class is an <code>ApplicationContextInitializer</code>.</p>
|
|
</li>
|
|
<li>
|
|
<p>The <code>@Bean</code> methods have been converted to calls to <code>context.registerBean()</code></p>
|
|
</li>
|
|
<li>
|
|
<p>The <code>@SpringBootApplication</code> has been replaced with
|
|
<code>@SpringBootConfiguration</code> to signify that we are not enabling Spring
|
|
Boot autoconfiguration, and yet still marking the class as an "entry
|
|
point".</p>
|
|
</li>
|
|
<li>
|
|
<p>The <code>SpringApplication</code> from Spring Boot has been replaced with a
|
|
<code>FunctionalSpringApplication</code> from Spring Cloud Function (it’s a
|
|
subclass).</p>
|
|
</li>
|
|
</ul>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>The business logic beans that you register in a Spring Cloud Function app are of type <code>FunctionRegistration</code>.
|
|
This is a wrapper that contains both the function and information about the input and output types. In the <code>@Bean</code>
|
|
form of the application that information can be derived reflectively, but in a functional bean registration some of
|
|
it is lost unless we use a <code>FunctionRegistration</code>.</p>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>An alternative to using an <code>ApplicationContextInitializer</code> and <code>FunctionRegistration</code> is to make the application
|
|
itself implement <code>Function</code> (or <code>Consumer</code> or <code>Supplier</code>). Example (equivalent to the above):</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootConfiguration
|
|
public class DemoApplication implements Function<String, String> {
|
|
|
|
public static void main(String[] args) {
|
|
FunctionalSpringApplication.run(DemoApplication.class, args);
|
|
}
|
|
|
|
@Override
|
|
public String apply(String value) {
|
|
return value.toUpperCase();
|
|
}
|
|
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>It would also work if you add a separate, standalone class of type <code>Function</code> and register it with
|
|
the <code>SpringApplication</code> using an alternative form of the <code>run()</code> method. The main thing is that the generic
|
|
type information is available at runtime through the class declaration.</p>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>Suppose you have</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@Component
|
|
public class CustomFunction implements Function<Flux<Foo>, Flux<Bar>> {
|
|
@Override
|
|
public Flux<Bar> apply(Flux<Foo> flux) {
|
|
return flux.map(foo -> new Bar("This is a Bar object from Foo value: " + foo.getValue()));
|
|
}
|
|
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>You register it as such:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@Override
|
|
public void initialize(GenericApplicationContext context) {
|
|
context.registerBean("function", FunctionRegistration.class,
|
|
() -> new FunctionRegistration<>(new CustomFunction()).type(CustomFunction.class));
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_limitations_of_functional_bean_declaration"><a class="link" href="#_limitations_of_functional_bean_declaration">Limitations of Functional Bean Declaration</a></h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph">
|
|
<p>Most Spring Cloud Function apps have a relatively small scope compared to the whole of Spring Boot,
|
|
so we are able to adapt it to these functional bean definitions easily. If you step outside that limited scope,
|
|
you can extend your Spring Cloud Function app by switching back to <code>@Bean</code> style configuration, or by using a hybrid
|
|
approach. If you want to take advantage of Spring Boot autoconfiguration for integrations with external datastores,
|
|
for example, you will need to use <code>@EnableAutoConfiguration</code>. Your functions can still be defined using the functional
|
|
declarations if you want (i.e. the "hybrid" style), but in that case you will need to explicitly switch off the "full
|
|
functional mode" using <code>spring.functional.enabled=false</code> so that Spring Boot can take back control.</p>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<h1 id="_testing_functional_applications" class="sect0"><a class="link" href="#_testing_functional_applications">Testing Functional Applications</a></h1>
|
|
<div class="openblock partintro">
|
|
<div class="content">
|
|
<div class="paragraph">
|
|
<p>Spring Cloud Function also has some utilities for integration testing that will be very familiar to Spring Boot users.</p>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>Suppose this is your application:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootApplication
|
|
public class SampleFunctionApplication {
|
|
|
|
public static void main(String[] args) {
|
|
SpringApplication.run(SampleFunctionApplication.class, args);
|
|
}
|
|
|
|
@Bean
|
|
public Function<String, String> uppercase() {
|
|
return v -> v.toUpperCase();
|
|
}
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>Here is an integration test for the HTTP server wrapping this application:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootTest(classes = SampleFunctionApplication.class,
|
|
webEnvironment = WebEnvironment.RANDOM_PORT)
|
|
public class WebFunctionTests {
|
|
|
|
@Autowired
|
|
private TestRestTemplate rest;
|
|
|
|
@Test
|
|
public void test() throws Exception {
|
|
ResponseEntity<String> result = this.rest.exchange(
|
|
RequestEntity.post(new URI("/uppercase")).body("hello"), String.class);
|
|
System.out.println(result.getBody());
|
|
}
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>or when function bean definition style is used:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@FunctionalSpringBootTest
|
|
public class WebFunctionTests {
|
|
|
|
@Autowired
|
|
private TestRestTemplate rest;
|
|
|
|
@Test
|
|
public void test() throws Exception {
|
|
ResponseEntity<String> result = this.rest.exchange(
|
|
RequestEntity.post(new URI("/uppercase")).body("hello"), String.class);
|
|
System.out.println(result.getBody());
|
|
}
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>This test is almost identical to the one you would write for the <code>@Bean</code> version of the same app - the only difference
|
|
is the <code>@FunctionalSpringBootTest</code> annotation, instead of the regular <code>@SpringBootTest</code>. All the other pieces,
|
|
like the <code>@Autowired</code> <code>TestRestTemplate</code>, are standard Spring Boot features.</p>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>And to help with correct dependencies here is the excerpt from POM</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-xml hljs" data-lang="xml"> <parent>
|
|
<groupId>org.springframework.boot</groupId>
|
|
<artifactId>spring-boot-starter-parent</artifactId>
|
|
<version>2.2.2.RELEASE</version>
|
|
<relativePath/> <!-- lookup parent from repository -->
|
|
</parent>
|
|
. . . .
|
|
<dependency>
|
|
<groupId>org.springframework.cloud</groupId>
|
|
<artifactId>spring-cloud-function-web</artifactId>
|
|
<version>3.0.1.BUILD-SNAPSHOT</version>
|
|
</dependency>
|
|
<dependency>
|
|
<groupId>org.springframework.boot</groupId>
|
|
<artifactId>spring-boot-starter</artifactId>
|
|
</dependency>
|
|
<dependency>
|
|
<groupId>org.springframework.boot</groupId>
|
|
<artifactId>spring-boot-starter-web</artifactId>
|
|
<scope>test</scope>
|
|
</dependency>
|
|
<dependency>
|
|
<groupId>org.springframework.boot</groupId>
|
|
<artifactId>spring-boot-starter-test</artifactId>
|
|
<scope>test</scope>
|
|
<exclusions>
|
|
<exclusion>
|
|
<groupId>org.junit.vintage</groupId>
|
|
<artifactId>junit-vintage-engine</artifactId>
|
|
</exclusion>
|
|
</exclusions>
|
|
</dependency></code></pre>
|
|
</div>
|
|
</div>
|
|
<div class="paragraph">
|
|
<p>Or you could write a test for a non-HTTP app using just the <code>FunctionCatalog</code>. For example:</p>
|
|
</div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@RunWith(SpringRunner.class)
|
|
@FunctionalSpringBootTest
|
|
public class FunctionalTests {
|
|
|
|
@Autowired
|
|
private FunctionCatalog catalog;
|
|
|
|
@Test
|
|
public void words() throws Exception {
|
|
Function<String, String> function = catalog.lookup(Function.class,
|
|
"uppercase");
|
|
assertThat(function.apply("hello")).isEqualTo("HELLO");
|
|
}
|
|
|
|
}</code></pre>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<script type="text/javascript" src="js/tocbot/tocbot.min.js"></script>
|
|
<script type="text/javascript" src="js/toc.js"></script>
|
|
<link rel="stylesheet" href="js/highlight/styles/github.min.css">
|
|
<script src="js/highlight/highlight.min.js"></script>
|
|
<script>hljs.initHighlighting()</script>
|
|
</body>
|
|
</html> |