Add runApplication() Kotlin top level function #10511

sdeleuze · 2017-10-04T17:05:26Z

Since Kotlin extensions do not apply to static methods, this commit introduces a runApplication() Kotlin top level function that acts as a Kotlin shortcut for SpringApplication.run().

This shortcut avoids to require using non-idiomatic code like SpringApplication.run(FooApplication::class.java) and provides a runApplication<FooApplication>() alternative (as well as an array of KClass based alternative when multiple classes need to be passed as parameter).

This commit also adds Kotlin main artifacts to Spring Boot dependency management and will be replaced by Kotlin BOM when it will be available (see KT-18398).

runApplication<FooApplication>() is a form usually preferred in Kotlin to runApplication(FooApplication::class) and consistent with what we do on Spring Framework side.

The custom Maven configuration is the typical way to deal with Java + Kotlin project, a similar configuration has been applied to Spring Data Kay.

Closes gh-8511

sdeleuze · 2017-10-04T19:57:29Z

The build failed for an unrelated flacky WebFlux test, but ./mvnw clean install works fine locally and I have validated the top level function is usable in my MiXiT sample application.

snicoll

Thanks for the PR, I've added a few suggestions.

Generally speaking, I am a bit nervous about the maven compiler plugin setup and the impacts on the IDE integration.

snicoll · 2017-10-05T08:15:29Z

spring-boot-dependencies/pom.xml

+			</dependency>
+			<dependency>
+				<groupId>org.jetbrains.kotlin</groupId>
+				<artifactId>kotlin-stdlib-jre7</artifactId>


We don't support Java 7 so that should go away.

I'm not sure I agree with that. I'd rather that the dependency management was complete.

I am not following. When are we going to use that dependency if we don't support Java 7 anymore?

We support Java 8 so kotlin-stdlib, kotlin-stdlib-jre7 and kotlin-stdlib-jre8 should be specified for consistent versioning. kotlin-stdlib contains all methods usable on Java 6, kotlin-stdlib-jre7 contains Java 7 specific methods which are needed for Java 8 support, same for kotlin-stdlib-jre8 and Java 8 specific methods.

snicoll · 2017-10-05T08:16:14Z

spring-boot/pom.xml

+					<parameters>true</parameters>
+				</configuration>
+				<executions>
+					<execution>


What are those? Can you explain?

Scratch that. I didn't read your description properly, sorry.

snicoll · 2017-10-05T08:17:21Z

spring-boot/src/test/kotlin/org/springframework/boot/SpringApplicationExtensionsTests.kt

+
+		@Bean
+		open fun webServer(): TomcatServletWebServerFactory {
+			return TomcatServletWebServerFactory(0)


Is there a reason why you need to create a web server for this test? That looks a bit overkill to me.

Yes, because if not the test fails, I just copied what you do in SpringApplicationTests on Java side.

sdeleuze · 2017-10-05T16:50:24Z

For Maven plugin configuration, it is the standard way to compile Java + Kotlin projects, I have on purpose only applied it to the module where we need that, we do the same in Spring Data without issues reported, and many other project do that. If you face issue, I can ask Kotlin team to fixit, if not I would recommand go that way since I have no alternative to propose.

sdeleuze · 2017-10-06T08:52:47Z

Hum, there is already a kotlin.run top level function, so reusing that name for Boot may cause confusion. I will update the PR with another function name.

sdeleuze · 2017-10-06T09:01:48Z

I have splitted this PR in 2 commits, one for dependency management, the other for the extension itself. I have also renamed the top level function to runApplication() which seems to me a good trade off between run() which will cause confusion with kotlin.run() and looks reasonably short (runSpringApplication() looks ugly for such widely used function).

sdeleuze · 2017-10-06T09:34:49Z

I have also rebased this PR on top of the recent module structure changes.

GreyTeardrop · 2017-10-20T08:45:07Z

Hi! Awesome to see even more Kotlin niceties in Boot!

@sdeleuze,
Do you think it could make sense to also add something like this:

inline fun <reified T : Any> runApplication(vararg args: String,
                                            block: SpringApplication.() -> Unit): ConfigurableApplicationContext =
    SpringApplication(T::class.java).apply(block).run(*args)

for cases when some SpringApplication tuning is required?

sdeleuze · 2017-10-20T09:56:14Z

@GreyTeardrop Great idea, this makes this feature much more flexible.

@snicoll I have updated the PR with this proposal and added related tests. I have also created the related #10712 issue.

This commit adds Kotlin main artifacts to Spring Boot dependency management and will be replaced by Kotlin BOM when it will be available (see KT-18398). gh-9486

Since Kotlin extensions do not apply to static methods, this commit introduces a runApplication() Kotlin top level function that acts as a Kotlin shortcut for SpringApplication.run(). This shortcut avoids to require using non-idiomatic code like SpringApplication.run(FooApplication::class.java) and provides a runApplication<FooApplication>() alternative (as well as an array of KClass based alternative when multiple classes need to be passed as parameter). It is possible to customize the application with the following syntax: runApplication<FooApplication>() { setEnvironment(environment) } Closes gh-8511

gh-9486

sdeleuze · 2017-10-25T08:44:51Z

I have added plugin management for Maven plugin, after discussion with @wilkinsona sadly we can't do similar things with Gradle plugin. Unfortunate but IMO we can live with that, it is possible to have different minor versions between dependencies and plugin.

snicoll · 2017-10-25T08:59:28Z

@wilkinsona this would require a Spring Boot version to Kotlin version mapping in start.spring.io for Gradle projecs and I am really not keen to add that.

Would it be possible to extrac the kotlin.version from the BOM and use that as a property to define the version of the plugin to use? Or do something of the kind in our own dependency management plugin?

wilkinsona · 2017-10-25T09:15:06Z

I'd have to investigate, but right now I don't know how to do it, particularly with the plugins DSL. We can only extract the kotlin.version from the bom once the Spring Boot and Dependency Management plugins have been applied. By that point, the Kotlin plugin may already have been applied too. I think there's a chicken and egg problem here.

wilkinsona · 2017-10-25T09:18:12Z

We avoid the problem for the Dependency Management plugin by making the Spring Boot plugin pull it in transitively. That lets us control the version of the Dependency Management plugin and allows a user to just apply the plugin without worrying about its version. We could do the same for the Kotlin plugin, but then everyone building a Gradle project would download the Kotlin plugin even if they weren't using it. That's similar to what we did for Jackson's Kotlin module so we could decide that it's a reasonable thing to do, probably depending on the weight of the Kotlin plugin and its dependencies.

Since Kotlin extensions do not apply to static methods, this commit introduces a runApplication() Kotlin top level function that acts as a Kotlin shortcut for SpringApplication.run(). This shortcut avoids to require using non-idiomatic code like SpringApplication.run(FooApplication::class.java) and provides a runApplication<FooApplication>() alternative (as well as an array of KClass based alternative when multiple classes need to be passed as parameter). It is possible to customize the application with the following syntax: runApplication<FooApplication>() { setEnvironment(environment) } See spring-projectsgh-10511

Closes spring-projectsgh-10511

Since Kotlin extensions do not apply to static methods, this commit introduces a runApplication() Kotlin top level function that acts as a Kotlin shortcut for SpringApplication.run(). This shortcut avoids to require using non-idiomatic code like SpringApplication.run(FooApplication::class.java) and provides a runApplication<FooApplication>() alternative (as well as an array of KClass based alternative when multiple classes need to be passed as parameter). It is possible to customize the application with the following syntax: runApplication<FooApplication>() { setEnvironment(environment) } See gh-10511

* pr/10511: Polish "Add runApplication() Kotlin top level function" Specify kotlin-maven-plugin version for plugin management Add runApplication() Kotlin top level function Add Kotlin main artifacts to dependency management

See gh-10511

See spring-projects/spring-boot#10511

philwebb · 2017-11-01T03:34:18Z

I'm guessing 90% of applications are going to do something like this:

fun main(args : Array<String>) { 
    runApplication<ExampleApp>(args)
}

I'm wondering if we shouldn't drop the multiple config version? Doing this:

runApplication(arrayOf(ExampleConfig::class, ExampleWebConfig::class), args)

Doesn't seem much better than:

SpringApplication(ExampleConfig::class, ExampleWebConfig::class).run(args)

@sdeleuze Are there any benefits to the arrayOf version that I'm missing?

sdeleuze · 2017-11-01T20:20:06Z

@philwebb Good point, indeed I think we can remove the Array variant.

philwebb · 2017-11-01T20:29:54Z

I'll take care of that

sdeleuze mentioned this pull request Oct 4, 2017

Provide support for Kotlin KClass parameter in SpringApplication.run() #8511

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spring-projects-issues added the status: waiting-for-triage An issue we've not yet triaged label Oct 4, 2017

philwebb force-pushed the master branch from dc8c2d0 to 33edfda Compare October 5, 2017 03:19

snicoll requested changes Oct 5, 2017

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sdeleuze changed the title ~~Add run() Kotlin top level function~~ Add runApplication() Kotlin top level function Oct 6, 2017

sdeleuze mentioned this pull request Oct 6, 2017

Use Kotlin's bom to provide dependency management for Kotlin #9486

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snicoll approved these changes Oct 7, 2017

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snicoll added priority: normal type: enhancement A general enhancement and removed status: waiting-for-triage An issue we've not yet triaged labels Oct 7, 2017

snicoll added this to the 2.0.0.M6 milestone Oct 7, 2017

sdeleuze mentioned this pull request Oct 13, 2017

The value of a manifest attribute must not be null (Key=Start-Class #10621

Closed

sdeleuze added 3 commits October 25, 2017 09:58

Add Kotlin main artifacts to dependency management

d7cf668

This commit adds Kotlin main artifacts to Spring Boot dependency management and will be replaced by Kotlin BOM when it will be available (see KT-18398). gh-9486

Specify kotlin-maven-plugin version for plugin management

a92e7de

gh-9486

snicoll self-assigned this Oct 26, 2017

snicoll added a commit to snicoll/spring-boot that referenced this pull request Oct 27, 2017

Polish "Add runApplication() Kotlin top level function"

3c3ca10

Closes spring-projectsgh-10511

snicoll mentioned this pull request Oct 27, 2017

Add support for runApplication top-level function spring-io/initializr#534

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snicoll closed this in fd07bfd Oct 27, 2017

wilkinsona added a commit that referenced this pull request Oct 27, 2017

Manage the version of Kotlin's kotlin-runtime module

708f917

See gh-10511

sdeleuze added a commit to sdeleuze/spring-kotlin-deepdive that referenced this pull request Oct 28, 2017

Use runApplication top level function

18d1a03

See spring-projects/spring-boot#10511

sdeleuze added a commit to sdeleuze/spring-kotlin-deepdive that referenced this pull request Oct 28, 2017

Use runApplication top level function

1feb77d

See spring-projects/spring-boot#10511

sdeleuze added a commit to sdeleuze/spring-kotlin-deepdive that referenced this pull request Oct 28, 2017

Use runApplication top level function

d2593c8

See spring-projects/spring-boot#10511

philwebb reopened this Nov 1, 2017

GreyTeardrop mentioned this pull request Nov 1, 2017

Expose the functional bean registration API via SpringApplication #8115

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snicoll closed this in e28b98c Nov 2, 2017

sdeleuze mentioned this pull request Feb 9, 2018

Improve Kotlin support #5537

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Add runApplication() Kotlin top level function #10511

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