Deploying Your Application

Using the Dist Task 👩‍🏫

Except for a java installation on the server, the dist task creates a binary version of the application that you can deploy to a server without relying on sbt.

In the play console, type dist:

[my-app] $ dist

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And you will find something similar to this:

$ sbt
[info] Loading global plugins from /Users/play-developer/.sbt/0.13/plugins
[info] Loading project definition from /Users/play-developer/my-app/project
[info] Set current project to my-app (in build file:/Users/play-developer/my-app/)
[my-app] $ dist
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-sources.jar ...
[info] Done packaging.
[info] Wrote /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT.pom
[info] Main Scala API documentation to /Users/play-developer/my-first-app/target/scala-2.13/api...
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-web-assets.jar ...
[info] Done packaging.
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT.jar ...
[info] Done packaging.
model contains 21 documentable templates
[info] Main Scala API documentation successful.
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-javadoc.jar ...
[info] Done packaging.
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-sans-externalized.jar ...
[info] Done packaging.
[info]
[info] Your package is ready in /Users/play-developer/my-first-app/target/universal/my-first-app-1.0-SNAPSHOT.zip
[info]
[success] Total time: 5 s, completed Feb 6, 2017 2:08:44 PM
[my-app] $

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This results in a ZIP file that contains all of the JAR files required to run your application in the target/universal folder.

On the target server, unzip the file before running the script in the bin directory to launch the application. The script has two versions: a Windows.bat script and a bash shell script with the same name as your program

$ unzip my-app-1.0.zip
$ my-app-1.0/bin/my-first-app -Dplay.http.secret.key=ad31779d4ee49d5ad5162bf1429c32e2e9933f3b

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From the command line, you can also supply a different configuration file for a production environment:

$ my-app-1.0/bin/my-app -Dconfig.file=/full/path/to/conf/application-prod.conf

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Start the script with the -h option to see a detailed usage description.

The dist process automatically includes the API documentation in the resulting package. Add these lines to build.sbt even if they are not required:

sources in (Compile, doc) := Seq.empty
publishArtifact in (Compile, packageDoc) := false

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The preceding statement must be applied to all sub-project definitions for builds containing sub-projects.

The Native Packager👨‍🎓

The sbt Native Packager plugin is used by play. The dist task to build a zip file is declared by the native packager plugin. The following are directly equivalent to calling the dist task:

[my-app] $ universal:packageBin

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Other kinds of archives that can be created include:

💡tar.gz

💡OS X disk images

💡Microsoft Installer (MSI)

💡RPMs

💡Debian packages

💡System V / init.d and Upstart services in RPM/Debian packages.

Build a server distribution🚀

The sbt-native-packager plugins offer a variety of archetypes. The java server pattern, which play by default employs, makes it possible to use the following features:

⭐System V or Upstart startup scripts

⭐Default folders

Minimal Debian settings

Include the following construction settings:

lazy val root = (project in file("."))
  .enablePlugins(PlayScala, DebianPlugin)

maintainer in Linux := "Coding Ninjas <Coding.Ninjas@example.com>"

packageSummary in Linux := "My Coding Ninjas package summary"

packageDescription := "My Coding Ninjas package description"

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Then build your package with:

[my-app] $ debian:packageBin

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Minimal RPM settings

Add the following settings to your build:
lazy val root = (project in file("."))
  .enablePlugins(PlayScala, RpmPlugin)

maintainer in Linux := "Coding Ninjas <Coding.Ninjas@example.com>"

packageSummary in Linux := "My Coding Ninjas package summary"

packageDescription := "My lCoding Ninjas package description"

rpmRelease := "1"

rpmVendor := "example.com"

rpmUrl := Some("http://github.com/example/server")

rpmLicense := Some("Apache v2")

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Then build your package with:

[my-app] $ rpm:packageBin

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Including Additional Files in Your Distribution📁

Anything contained in the dist directory of your project will be made available in the distribution created by the native packager. You should note that the src/universal directory specified in the native packager's documentation has a counterpart in play's dist directory.

Play PID Configuration🕝

The Production setup describes how Play manages its own PID.

play uses a different pidfile; therefore, we must provide it with the correct path, which in this case is packageName.value. The only acceptable pid file name is play.pid. Place a file called application.ini within the dist/conf folder and add the following information to it so the startup script will know where to look for the PID file:

s"-Dpidfile.path=/var/run/${packageName.value}/play.pid",
# Add all other startup settings here, too

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To prevent play from creating a PID just set the property to /dev/null:

-Dpidfile.path=/dev/null

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Publishing to a Maven (or Ivy) Repository🧐

Your application can also be uploaded to a Maven repository. This publishes both the POM file and the JAR file containing your application.

In your build.sbt file, you must configure the repository you wish to publish to:

publishTo := Some(
  "My resolver".at("https://CodingNinjas.com/repo")
)

credentials += Credentials(
  "Repo",
  "https://CodingNinjas.com/repo",
  "admin",
  "admin123"
)

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Then in the play console, use the publish task:

[my-app] $ publish

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Running a Production Server in Place👨‍🏫

In some cases, you might prefer to launch your application directly from the source directory of your project rather than producing a complete distribution. The stage task can be used to do the necessary sbt installation on the server.

$ sbt clean stage

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You will see something similar to this:

$ sbt
[info] Loading global plugins from /Users/play-developer/.sbt/0.13/plugins
[info] Loading project definition from /Users/play-developer/my-first-app/project
[info] Set current project to my-first-app (in build file:/Users/play-developer/my-first-app/)
[my-first-app] $ stage
[info] Updating {file:/Users/play-developer/my-first-app/}root...
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-sources.jar ...
[info] Done packaging.
[info] Wrote /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT.pom
[info] Resolving jline#jline;2.12.2 ...
[info] Done updating.
[info] Main Scala API documentation to /Users/play-developer/my-first-app/target/scala-2.13/api...
[info] Compiling 8 Scala sources and 1 Java source to /Users/play-developer/my-first-app/target/scala-2.13/classes...
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-web-assets.jar ...
[info] Done packaging.
model contains 21 documentable templates
[info] Main Scala API documentation successful.
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-javadoc.jar ...
[info] Done packaging.
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT.jar ...
[info] Done packaging.
[info] Packaging /Users/play-developer/my-first-app/target/scala-2.13/my-first-app_2.13-1.0-SNAPSHOT-sans-externalized.jar ...
[info] Done packaging.
[success] Total time: 8 s, completed Feb 6, 2017 2:11:10 PM
[my-app] $

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Your application is cleaned up, compiled, and the necessary dependencies are located and copied to the target/universal/stage directory. Additionally, it generates a bin/start script, where start stands for the project name. There is a similar bat file for Windows, and the script operates the play server for Unix-style systems.

For instance, to launch the project my-first-application app's from the project folder, you can:

$ target/universal/stage/bin/my-first-app -Dplay.http.secret.key=ad31779d4ee49d5ad5162bf1429c32e2e9933f3b

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From the command line, you can also supply a different configuration file for a production environment:

$ target/universal/stage/bin/my-first-app -Dconfig.file=/full/path/to/conf/application-prod.conf

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Running a test instance🧑‍💻

The play offers a practical tool for launching a test application in production mode.

Run runProd to launch a program in production mode.

[my-app] $ runProd

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Using the sbt Assembly Plugin💥

The sbt assembly plugin can also be used to package and run Play applications even though it is not officially supported. One jar will be created as an output artifact, and you'll be able to run it using the java command.

To use it, include this dependency in your project's plugins.sbt file:

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.5")

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Add the following configuration now to your build.sbt file:

mainClass in assembly := Some("play.core.server.ProdServerStart")
fullClasspath in assembly += Attributed.blank(PlayKeys.playPackageAssets.value)

assemblyMergeStrategy in assembly := {
  case manifest if manifest.contains("MANIFEST.MF") =>
  
    MergeStrategy.discard
  case referenceOverrides if referenceOverrides.contains("reference-overrides.conf") =>
    // Keep the content for all reference-overrides.conf files
    MergeStrategy.concat
  case x =>
    // For all the other files, use the default sbt-assembly merge strategy
    val oldStrategy = (assemblyMergeStrategy in assembly).value
    oldStrategy(x)
}

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Now that the artifact has been built, you may launch your application by typing:

$ java -Dplay.http.secret.key=ad31779d4ee49d5ad5162bf1429c32e2e9933f3b -jar target/scala-2.XX/<yourprojectname>-assembly-<version>.jar

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Of course, you'll need to change the project name, version, and scala version.

We hope you understood everything about deploying your application in the play framework.🤗

Frequently Asked Questions

What do you mean by the iterator in the play framework?

The iterator interface provides an alternative method for iterating through any collection. So, getting an iterator instance from a collection is simple using the iterator technique. In the Java collection framework, the iterator replaces enumeration. The caller may also delete components from the underlying collection as the iteration is happening.

What is the difference between an enumeration and an iterator interface?

A relatively small amount of memory is consumed by an enumeration, which is twice as quick as an iterator. Very fundamental and appropriate use of enumeration is for meeting basic needs. However, the Iterator is more secure than enumeration since it never permits other threads to alter the group object while it is being iterated. Iterators allow for the destruction of underlying elements, which is not feasible with enumeration.

Can you describe the steps in building a new Scala application utilizing the Play framework?

You must use Scala's "activator" command to start a new application utilizing the play framework. This will produce a few files that you will need to change to customize your application and a new directory structure for your project.

Are there any restrictions while using the play framework to create JSON objects? 

There are indeed some restrictions. For instance, you cannot utilize the pay framework to produce a JSON object with duplicate keys.

What do you know about the play framework's asynchronous processing?

play framework's asynchronous processing features let you handle several requests concurrently. This can be helpful if you need to handle many requests rapidly or if you don't want to block one request while you wait for another to complete.

Conclusion

This article taught us how to deploy an application in the play framework. We began with a brief introduction to the method, followed by a detailed code example.

After reading about deploying an application in the play framework, refer to play documentation, play Framework Wikipedia, Introduction to play framework in Java, and 15 Best Java frameworks to use in 2022-Coding Ninjas or a deeper understanding of Play development and other related topics.

Refer to our guided paths on Coding Ninjas Studio to learn more about DSA, Competitive Programming, JavaScript, System Design, etc. Enroll in our courses and refer to the mock test and problems available. Take a look at the interview experiences and interview bundle for placement preparations.