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§Play 2.8 Migration Guide

This guide is for migrating from Play 2.7 to Play 2.8. See the Play 2.7 Migration Guide to upgrade from Play 2.6. It is also recommended to read Akka 2.5 to 2.6 migration guide since multiple changes there have an impact on Play 2.8.

§How to migrate

Before starting sbt, make sure to make the following upgrades.

§Play update

Update the Play version number in project/plugins.sbt:

addSbtPlugin("com.typesafe.play" % "sbt-plugin" % "2.8.x")

Where the “x” in 2.8.x is the minor version of Play you want to use, for instance 2.8.0.

§sbt upgrade

Although Play 2.8 still supports sbt 0.13, we recommend that you use sbt 1. This new version is supported and actively maintained. To update, change your project/build.properties so that it reads:

sbt.version=1.3.10

At the time of this writing 1.3.10 is the latest version in the sbt 1.x family, you may be able to use newer versions too. Check the release notes for both Play’s minor version releases and sbt’s releases for details.

§API Changes

Play 2.8 contains multiple API changes. As usual, we follow our policy of deprecating existing APIs before removing them. This section details these changes.

§SSLEngineProvider makes SSLContext visible

When configuring HTTPS, it is possible to override the play.server.SSLEngineProvider if you need to fully configure the SSL certificates. Before Play 2.8.0, the provider only made the SSLEngine visible. Now, to better integrate with third-party libraries, the SSLContext must be visible as well. See more details at ConfiguringHttps page.

§Scala 2.11 support discontinued

Play 2.8 support Scala 2.12 and 2.13, but not 2.11, which has reached its end of life.

§Setting scalaVersion in your project

Both Scala and Java users must configure sbt to use Scala 2.12 or 2.13. Even if you have no Scala code in your project, Play itself uses Scala and must be configured to use the right Scala libraries.

To set the Scala version in sbt, simply set the scalaVersion key, for example:

scalaVersion := "2.13.14"

If you have a single project build, then this setting can just be placed on its own line in build.sbt. However, if you have a multi-project build, then the scala version setting must be set on each project. Typically, in a multi-project build, you will have some common settings shared by every project, this is the best place to put the setting, for example:

def commonSettings = Seq(
  scalaVersion := "2.13.14"
)

val projectA = (project in file("projectA"))
  .enablePlugins(PlayJava)
  .settings(commonSettings)

val projectB = (project in file("projectB"))
  .enablePlugins(PlayJava)
  .settings(commonSettings)

§File serving methods changed the type of their filename parameters

Methods for serving files, like ok(File content, ...) (and similar) in the Java API or sendFile, sendPath and sendResource in both Java’s StatusHeader and Scala’s Status class changed the type of their filename parameters: Instead of using a plain String, the Scala API now uses an Option[String] as return type for its filename parameter function. The Java API changed the parameter type to be an Optional<String>.
This API change better reflects the fact that you can pass None / Optional.empty() if you don’t want the Content-Disposition header to include a filename.

§The Headers class of the Java API is immutable

The class play.mvc.Http.Headers is immutable now. Some methods have been deprecated and were replaced with new ones:

Deprecated method New method
toMap() asMap()
addHeader(String name, String value) adding(String name, String value)
addHeader(String name, List<String> values) adding(String name, List<String> values)
remove(String name) removing(String name)

Be aware that the old deprecated methods return the original, modified Headers object, whereas the new methods always return a new object, leaving the original object unmodified.

§Deprecated APIs were removed

Many APIs that were deprecated in earlier versions were removed in Play 2.8. If you are still using them we recommend migrating to the new APIs before upgrading to Play 2.8. Check the Javadocs and Scaladocs for migration notes. See also the migration guide for Play 2.7 for more information.

§Java API

In Play 2.7 we deprecate play.mvc.Http.Context in favor of directly using play.mvc.Http.RequestHeader or play.mvc.Http.Request. We have now removed Http.Context and if your application depends on it, you should read Play 2.7 migration guide instructions.

§Cache Api changes

§Configuration changes

This section lists changes and deprecations in configurations.

§ObjectMapper serialization change

Play 2.8 adopts Akka Jackson Serialization support and then uses the defaults provided by Akka. One of the changes is how Java Time types are rendered. Until Play 2.7 they were rendered as timestamps, which has better performance, but now they are rendered using ISO-8601 (rfc3339) format (yyyy-MM-dd'T'HH:mm:ss.SSSZ).

If you need to use the old timestamps default format, then add the following configuration in your application.conf:

akka.serialization.jackson.play.serialization-features {
  WRITE_DATES_AS_TIMESTAMPS = on
  WRITE_DURATIONS_AS_TIMESTAMPS = on
}

Play-provided instances of ObjectMapper (either using Json#newDefaultMapper or Guice-managed play.core.ObjectMapperProvider) include a stack-efficient implementation of a Jackson deserializer to JsonNode. If you already use a custom deserializer to read json payloads into JsonNode you have two options:

  1. You can disable Play’s play.utils.JacksonJsonNodeModule from the ObjectMapper with the setting:
akka.serialization.jackson.play {
  jackson-modules = ${akka.serialization.jackson.jackson-modules}
  ##   Play's default settings concatenate "akka.serialization.jackson.jackson-modules" 
  ##      with "play.utils.JacksonJsonNodeModule" 
  ## jackson-modules = ${akka.serialization.jackson.jackson-modules} ["play.utils.JacksonJsonNodeModule"]
}
  1. You can go further and completely disable the play.core.ObjectMapperModule Guice module that binds
    the ObjectMapper to a Provider<ObjectMapper>. Then, you will have to create your
    own com.example.ObjectMapperModule and provide that binding.
play.modules.disabled += "play.core.ObjectMapperModule"
play.modules.enabled += "com.example.ObjectMapperModule"

§Dropped the overrides for akka.actor.default-dispatcher.fork-join-executor

The overrides that Play had under akka.actor.default-dispatcher.fork-join-executor have been dropped in favour of using Akka’s new-and-improved defaults.

See the section related to changes in the default dispatch in Akka’s migration guide for more details.

§IOSource and FileIO changes in Akka Streams

There are changes related to how Akka Streams handle errors for FileIO.toPath, StreamConverters.fromInputStream, and StreamConverters.fromOutputStream. See the section related to these changes in Akka’s migration guide for more details.

§Configuration loading changes

Until Play 2.7, when loading configuration, Play was not considering the default Java System Properties if the user provides some properties. Now, System Properties are always considered, meaning you can reference them in your application.conf file even if you are also defining custom properties. For example, when embedding Play like the code below, both userProperties and System Properties are used:

import java.util.Properties

import play.api.mvc.Results
import play.core.server.AkkaHttpServer
import play.core.server.ServerConfig
import play.api.routing.sird._

class MyApp {
  def main(args: Array[String]): Unit = {
    // Define some user properties here
    val userProperties = new Properties()
    userProperties.setProperty("my.property", "some value")

    val serverConfig = ServerConfig(properties = userProperties)

    val server = AkkaHttpServer.fromRouterWithComponents(serverConfig) { components => {
      case GET(p"/hello") => components.defaultActionBuilder {
        Results.Ok
      }
    }}
  }
}

Keep in mind that system properties override user-defined properties.

§Debugging SSL Connections

Until Play 2.7, both Play and Play-WS were using a version of ssl-config which had a debug system that relied on undocumented modification of internal JSSE debug settings. These are usually set using javax.net.debug and java.security.debug system properties on startup.

The debug system has been removed, and debug flags that do not have a direct correlation in the new system are deprecated, and the new configuration is documented in ssl-config docs.

§I18n behavior changes

Matching of languages behavior now satisfies RFC 4647.

§Example

conf/application.conf file:

play.i18n.langs = [ "fr", "fr-FR", "en", "en-US" ]

User’s accept-language:

en-GB
§Before

User’s accept-language en-GB does not match any of the conf. The play app responds French page against user’s will.

§After

User’s accept-language en-GB matches en. The play app responds English page.

§Generalized server backend configurations

Play comes with two server backends:

Until now, we kept these configurations separate, even if there were settings that applied to both backends and therefore were conclusively duplicates.
With Play 2.8 we start to generalize such duplicate server backend configurations and move them directly below play.server.*:

§The excludePaths config of the Redirect HTTPS filter changed

The play.filters.https.excludePaths config of the Redirect HTTPS filter now contains a list of paths instead of URIs. That means query params don’t matter anymore. If the list contains /foo the request /foo?abc=xyz will now be excluded too. Before Play 2.8, because the URI of a request (path + query params) was checked against the list, you needed to add exactly a request’s URI to exclude it from redirecting.

§Defaults changes

Some default values used by Play had changed and that can have an impact on your application. This section details the default changes.

§Content-Disposition: inline header not send anymore when serving files

When serving files via the Scala API or the Java API Play by default generates the Content-Disposition header automatically and sends it to the client.

Starting with Play 2.8 however, when the computed header ends up being exactly Content-Disposition: inline (when passing inline = true, which is the default, and null as file name), it won’t be send by Play automatically anymore. Because, according to RFC 6266 Section 4.2, rendering content inline is the default anyway.

Therefore, this change should not affect you at all, since all browsers adhere to the specs and do not treat this header in any special way but to render content inline, like no header was send.

If you still want to send this exact header however, you can still do that by using the withHeader(s) methods from Scala's or Java's Result class.

§Dependency graph changes

Until Play 2.7.0, "com.typesafe.play" %% "play-test" artifact was including both Akka HTTP and Netty server backends. This creates unstable behavior for your tests and, also, made them possibly use a different server than the production code, depending on how the classpath is sorted. In Play 2.8, play-test depends on play-server instead, and then the tests will use the same server provider that the application uses. If, for some reason, you need add a provider to our tests, you can do that by adding either Akka HTTP or Netty server dependencies as a "test" dependency. For example:

libraryDependencies += akkaHttpServer % "test" // Use nettyServer if you want the Netty Server backend

§Updated libraries

Besides updates to newer versions of our own libraries (play-json, play-ws, twirl, cachecontrol, etc), many other important dependencies were updated to the newest versions:

Next: Play 2.7