You are viewing the documentation for the 2.7.0-RC9 development release. The latest stable release series is 2.8.x.

§Play 2.7 Migration Guide

This is a guide for migrating from Play 2.6 to Play 2.7. If you need to migrate from an earlier version of Play then you must first follow the Play 2.6 Migration Guide.

§How to migrate

The following steps need to be taken to update your sbt build before you can load/run a Play project in sbt.

§Play upgrade

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

addSbtPlugin("" % "sbt-plugin" % "2.7.x")

Where the “x” in 2.7.x is the minor version of Play you want to use, for instance 2.7.0.

§sbt upgrade to 1.2.7

Although Play 2.7 still supports sbt 0.13 series, we recommend that you use sbt 1.x from now. This new version is actively maintained and supported. To update, change your project/ so that it reads:


At the time of this writing 1.2.7 is the latest version in the sbt 1.x family, you may be able to use newer versions too. Check for details in the release notes of your minor version of Play 2.7.x. More information at the list of sbt releases.

§API Changes

Multiple APIs changes were made following our policy of deprecating the existing APIs before removing them. This section details these changes.

§Deprecated APIs were removed

Many APIs that deprecated in earlier versions were removed in Play 2.7. If you are still using them, we recommend migrating to the new APIs before upgrading to Play 2.7. Both Javadocs and Scaladocs usually have proper documentation on how to migrate. See the migration guide for Play 2.6 for more information.

§StaticRoutesGenerator removed

The StaticRoutesGenerator, which was deprecated in 2.6.0, has been removed. If you are still using it, you will likely have to remove a line like this from your build.sbt file:

routesGenerator := StaticRoutesGenerator

§Java Http.Context changes

See changes made in play.mvc.Http.Context APIs. This is only relevant for Java users: Java `Http.Context` changes.

§Play WS API Changes

In Play 2.6, we extracted most of Play-WS into a standalone project that has an independent release cycle. Play-WS now has a significant release that requires some changes in Play itself.

§Scala API

  1. now returns an Option[Duration] instead of an Option[Int].

§Java API

  1. now returns an Optional<String> instead of a String.
  2. now returns an Optional<String> instead of a String.
  3. now returns an Optional<String> instead of a String.
  4. now returns an Optional<WSScheme instead of a WSScheme.
  5. now returns an Optional<WSSignatureCalculator> instead of a WSSignatureCalculator.
  6. now returns an Optional<Duration> instead of a long.
  7. was removed in favor of using
  8. now returns an Optional<Boolean> instead of a boolean.

Some new methods were added to improve the Java API too:

New method converts a response body into Source<ByteString, ?>. For example:

    .stream() // this returns a CompletionStage<StandaloneWSResponse>

Other methods that were added to improve Java API:

  1. returns the body configured for that request. It can be useful when implementing
  2. returns the method configured for that request.
  3. returns the WSAuth.
  4. sets the WSAuth for that request.
  5. gets the URI for that response.

§BodyParsers API consistency

The API for body parser was mixing Integer and Long to define buffer lengths which could lead to overflow of values. The configuration is now uniformed to use Long. It means that if you are depending on play.api.mvc.PlayBodyParsers.DefaultMaxTextLength for example, you then need to use a Long. As such, play.api.http.ParserConfiguration.maxMemoryBuffer is now a Long too.

§Java’s FilePart exposes the TemporaryFile for uploaded files

By default, uploading files via the multipart/form-data encoding uses a TemporaryFile API which relies on storing files in a temporary filesystem.
However, up until Play 2.6, you were not able to access that TemporaryFile directly, but only the File it backs:

Http.MultipartFormData<File> body = request.body().asMultipartFormData();
Http.MultipartFormData.FilePart<File> picture = body.getFile("picture");
if (picture != null) {
    File file = picture.getFile();

The getFile() method used above is now deprecated, and you should use getRef() instead, which provides you a TemporaryFile instance with some useful methods.
Starting with Play 2.7 the above code should be refactored to:

Http.MultipartFormData<TemporaryFile> body = request.body().asMultipartFormData();
Http.MultipartFormData.FilePart<TemporaryFile> picture = body.getFile("picture");
if (picture != null) {
    TemporaryFile tempFile = picture.getRef();
    File file = tempFile.path().toFile();

§Differentiate moveTo and copyTo in TemporaryFile

Until Play 2.5, moveTo method was actually making a copy of the file to the destination and deleting the source. There was a subtle change in Play 2.6 where the file was instead being moved atomically depending on certain conditions. For such cases, both the source and destination end up using the same inode and then deleting the source implies that the destination will be deleted too.

To make the API more clear around this, there are now moveTo and copyTo methods where copyTo always create a copy that does not share the same inode. So, if the application is configured to clean up temporary files (see documentation for Scala or Java) and you want to retain the destination, then use copyTo instead of moveTo. For example:

package controllers;

import play.libs.Files;
import play.mvc.*;

import java.nio.file.Paths;

public class UploadController extends Controller {

public Result upload(Http.Request request) {
    Http.MultipartFormData<Files.TemporaryFile> body = request.body().asMultipartFormData();
    Http.MultipartFormData.FilePart<Files.TemporaryFile> picture = body.getFile("picture");
    if (picture != null) {
        String fileName = picture.getFilename();
        String contentType = picture.getContentType();
        Files.TemporaryFile file = picture.getRef();

        // Use copyTo if you want to retain the file for sure when using the temporary file
        // reaper. Use moveTo if you are not using the reaper or don't care about keeping the files.
        file.copyTo(Paths.get("/tmp/picture/destination.jpg"), true);
        return ok("File uploaded");
    } else {
        return badRequest().flashing("error", "Missing file");


Scala : ```scala package controllers import java.nio.file.Paths import javax.inject.Inject import play.api.mvc._ class UploadController @Inject()(val controllerComponents: ControllerComponents) extends BaseController { def upload = Action(parse.multipartFormData) { request => request.body.file("picture").map { picture => val filename = Paths.get(picture.filename).getFileName // Use copyTo if you want to retain the file for sure when using the temporary file // reaper. Use moveTo if you are not using the reaper or don't care about keeping the files. picture.ref.copyTo(Paths.get(s"/tmp/picture/$filename"), replace = true) Ok("File uploaded") }.getOrElse { Redirect(routes.HomeController.index).flashing("error" -> "Missing file") } } }

§Guice compatibility changes

Guice was upgraded to version 4.2.2 (also see 4.2.1 and 4.2.0 release notes), which causes the following breaking changes:

§Static Logger singletons deprecated

Most static methods of the Java play.Logger and almost all methods of the Scala play.api.Logger singleton object have been deprecated. These singletons wrote to the application logger, which is referenced in logback.xml as:

<logger name="application" level="DEBUG" />

If you are concerned about changing your logging configuration, the simplest migration here is to define your own singleton “application” logger using Logger("application") (Scala) or Logger.of("application") (Java). All logs sent to this logger will work exactly like the Play singleton logger. While we don’t recommend this approach in general, it’s ultimately up to you. Play and Logback do not force you to use any specific naming scheme for your loggers.

If you are comfortable making some straightforward code changes and changing your logging configuration, we instead recommend you create a new logger for each class, with a name matching the class name. This allows you to configure different log levels for each class or package. For example, to set the log level for all com.example.models to the info level, you can set in logback.xml:

<logger name="com.example.models" level="INFO" />

To define the logger in each class, you can define:

import play.Logger;
private static final Logger.ALogger logger = Logger.of(YourClass.class);
import play.api.Logger
private val logger = Logger(classOf[YourClass])

For Scala, Play also provides a play.api.Logging trait that can be mixed into a class or trait to add the val logger: Logger automatically:

import play.api.Logging

class MyClass extends Logging {
  // `logger` is automaticaly defined by the `Logging` trait:"hello!")

Of course you can also just use SLF4J directly:

private static final Logger logger = LoggerFactory.getLogger(YourClass.class);
private val logger = LoggerFactory.getLogger(classOf[YourClass])

If you’d like a more concise solution when using SLF4J directly for Java, you may also consider Project Lombok’s @Slf4j annotation.

Note: org.slf4j.Logger, the logging interface of SLF4J, does not yet provide logging methods which accept lambda expression as parameters for lazy evaluation. play.Logger and play.api.Logger, which are mostly simple wrappers for org.slf4j.Logger, provide such methods however.

Once you have migrated away from using the application logger, you can remove the logger entry in your logback.xml referencing it:

<logger name="application" level="DEBUG" />

§Application Loader API changes

If you are using a custom ApplicationLoader there is a chance you are manually creating instances of this loader when running the tests. To do that, you first need to create an instance of ApplicationLoader.Context, for example:

val env = Environment.simple()
val context = ApplicationLoader.Context(
  environment = env,
  sourceMapper = None,
  webCommands = new DefaultWebCommands(),
  initialConfiguration = Configuration.load(env),
  lifecycle = new DefaultApplicationLifecycle()
val loader = new MyApplicationLoader()
val application = loader.load(context)

But the ApplicationLoader.Context apply method used in the code above is now deprecated and throws an exception when webCommands is not null. The new code should be:

val env = Environment.simple()
val context = ApplicationLoader.Context.create(env)
val loader = new GreetingApplicationLoader()
val application = loader.load(context)

§JPA removals and deprecations

The class play.db.jpa.JPA, which has been deprecated in Play 2.6 already, has finally been removed. Have a look at the Play 2.6 JPA Migration notes if you haven’t yet.

With this Play release even more JPA related methods and annotations have been deprecated:

Like already mentioned in the Play 2.6 JPA migration notes, please use a JPAApi injected instance as described in Using play.db.jpa.JPAApi instead of these deprecated methods and annotations.

§Router#withPrefix should always add a prefix

Previously, router.withPrefix(prefix) was meant to add a prefix to a router, but still allowed “legacy implementations” to update their existing prefix. Play’s SimpleRouter and other classes followed this behavior. Now all implementations have been updated to add the prefix, so router.withPrefix(prefix) should always return a router that routes s"$prefix/$path" the same way router routes path.

By default, routers are unprefixed, so this will only cause a change in behavior if you are calling withPrefix on a router that has already been returned by withPrefix. To replace a prefix that has already been set on a router, you must call withPrefix on the original unprefixed router rather than the prefixed version.

§Run Hooks

RunHook.afterStarted() no longer takes an InetSocketAddress as a parameter.

§All Java form validate methods need to be migrated to class-level constraints

The “old” validate methods of a Java form will not be executed anymore.
Like announced in the Play 2.6 Migration Guide you have to migrate such validate methods to class-level constraints.

Important: When upgrading to Play 2.7 you will not see any compiler warnings indicating that you have to migrate your validate methods (because Play executed them via reflection).

§Java Form, DynamicForm and FormFactory constructors changed

Constructors of the Form, DynamicForm and FormFactory classes (inside that were using a Validator param use a ValidatorFactory param instead now.
In addition to that, these constructors now also need a com.typesafe.config.Config param.
E.g. new Form(..., validator) becomes new Form(..., validatorFactory, config) now.
This change only effects you if you use the constructors to instantiate a form instead of just using formFactory.form(SomeForm.class) - most likely in tests.

§The Java Cache API get method has been deprecated in favor of getOptional

The getOptional methods of the Java cacheApi return their results wrapped in an Optional.

Changes in play.cache.SyncCacheApi:

deprecated method new method
<T> T get(String key) <T> Optional<T> getOptional(String key)

Changes in play.cache.AsyncCacheApi:

deprecated method new method
<T> CompletionStage<T> get(String key) <T> CompletionStage<Optional<T>> getOptional(String key)

§Server.getHandlerFor has moved to Server#getHandlerFor

The getHandlerFor method on the Server trait was used internally by the Play server code when routing requests. It has been removed and replaced with a method of the same name on the Server object.

§Java DI-agnostic Play Module API support added and all built-in Java Modules type changed

You can now create DI-agnostic Play Module with Java by extending play.inject.Module, which is more Java friendly as it is using Java APIs and coded in Java as well. Besides, all the existing built-in Java Modules, for example, play.inject.BuiltInModule and, are no longer extending Scala play.api.inject.Module but Java play.inject.Module.

Since Java play.inject.Module is a subclass of Scala play.api.inject.Module, the Module instances can still be used in the same way, except the interface is a little different:

public class MyModule extends play.inject.Module {
    public java.util.List<play.inject.Binding<?>> bindings(final play.Environment environment, final com.typesafe.config.Config config) {
        return java.util.Collections.singletonList(
            // Note: it is bindClass() but not bind()

§play.mvc.Results.TODO moved to play.mvc.Controller.TODO

All Play’s error pages have been updated to render a CSP nonce if the CSPFilter is present. This means that the error page templates must take a request as a parameter. In 2.6.x, the TODO field was previously rendered as a static result instead of an action with an HTTP context, and so may have been called outside the controller. In 2.7.0, the TODO field has been removed, and there is now a TODO(Http.Request request) method in play.mvc.Controller instead:

public abstract class Controller extends Results implements Status, HeaderNames {
    public static Result TODO(play.mvc.Http.Request request) {
        return status(NOT_IMPLEMENTED, views.html.defaultpages.todo.render(request.asScala()));

§Internal changes

Many changes have been made to Play’s internal APIs. These APIs are used internally and don’t follow a normal deprecation process. Changes may be mentioned below to help those who integrate directly with Play internal APIs.

§Configuration changes

§play.allowGlobalApplication defaults to false

play.allowGlobalApplication = false is set by default in Play 2.7.0. This means Play.current will throw an exception when called. You can set this to true to make Play.current and other deprecated static helpers work again, but be aware that this feature will be removed in future versions.

In the future, if you still need to use static instances of application components, you can use static injection to inject them using Guice, or manually set static fields on startup in your application loader. These approaches should be forward compatible with future versions of Play, as long as you are careful never to run apps concurrently (e.g., in tests).

Since Play.current is still called by some deprecated APIs, when using such APIs, you need to add the following line to your application.conf file:

play.allowGlobalApplication = true

For example, when using play.api.mvc.Action object with embedded Play and Scala Sird Router, it access the global state:

import play.api.mvc._
import play.api.routing.sird._
import play.core.server._

// It can also be NettyServer
val server = AkkaHttpServer.fromRouter() {
  // `Action` in this case is the `Action` object which access global state
  case GET(p"/") => Action {
    Results.Ok(s"Hello World")

The example above either needs you to configure play.allowGlobalApplication = true as explained before, or to be rewritten to:

import play.api._
import play.api.mvc._
import play.api.routing.sird._
import play.core.server._

// It can also be NettyServer
val server = AkkaHttpServer.fromRouterWithComponents() { components: BuiltInComponents => {
    case GET(p"/") => components.defaultActionBuilder {
      Results.Ok(s"Hello World")

§HikariCP will not fail fast

Play 2.7 changes the default value for HikariCP’s initializationFailTimeout to -1. That means your application will start even if the database is not available. You can revert to the old behavior by configuring initializationFailTimeout to 1 which will make the pool to fail fast.

If the application is using database Evolutions, then a connection is requested at application startup to verify if there are new evolutions to apply. So this will make the startup fail if the database is not available since a connection is being required. The timeout then will be defined by connectionTimeout (default to 30 seconds).

See more details at SettingsJDBC.

§CoordinatedShutdown configuration

The configuration akka.coordinated-shutdown.exit-jvm is not supported anymore. When that setting is enabled Play will not start, and an error will be logged. Play ships with default values for akka.coordinated-shutdown.* which should be suitable for most scenarios so it’s unlikely you’ll need to override them.

The configuration is not supported anymore and adding it does not affect the application shutdown. A warning is logged if it is present. Play now runs all the phases to ensure that all hooks registered in ApplicationLifecycle and all the tasks added to coordinated shutdown are executed. If you need to run CoordinatedShutdown from a specific phase, you can always do it manually:

import javax.inject.Inject


class Shutdown @Inject()(actorSystem: ActorSystem) {

  // Define your own reason to run the shutdown
  case object CustomShutdownReason extends Reason

  def shutdown() = {
    // Use a phase that is appropriated for your application
    val runFromPhase = Some(CoordinatedShutdown.PhaseBeforeClusterShutdown)
    val coordinatedShutdown = CoordinatedShutdown(actorSystem).run(CustomShutdownReason, runFromPhase)

And for Java:


import javax.inject.Inject;
import java.util.Optional;

class Shutdown {

    public static final CoordinatedShutdown.Reason customShutdownReason = new CustomShutdownReason();

    private final ActorSystem actorSystem;

    public Shutdown(ActorSystem actorSystem) {
        this.actorSystem = actorSystem;

    public void shutdown() {
        // Use a phase that is appropriated for your application
        Optional<String> runFromPhase = Optional.of(CoordinatedShutdown.PhaseBeforeClusterShutdown());
        CoordinatedShutdown.get(actorSystem).run(customShutdownReason, runFromPhase);

    public static class CustomShutdownReason implements CoordinatedShutdown.Reason {}

§Application Secret is checked for minimum length

The application secret configuration play.http.secret.key is checked for a minimum length in production. If the key is fifteen characters or fewer, a warning will be logged. If the key is eight characters or fewer, then an error is thrown and the configuration is invalid. You can resolve this error by setting the secret to at least 32 bytes of completely random input, such as head -c 32 /dev/urandom | base64 or by the application secret generator, using playGenerateSecret or playUpdateSecret.

The application secret is used as the key for ensuring that a Play session cookie is valid, i.e. has been generated by the server as opposed to spoofed by an attacker. However, the secret only specifies a string, and does not determine the amount of entropy in that string. Anyhow, it is possible to put an upper bound on the amount of entropy in the secret simply by measuring how short it is: if the secret is eight characters long, that is at most 64 bits of entropy, which is insufficient by modern standards.

§play.filters.headers.contentSecurityPolicy deprecated for CSPFilter

The SecurityHeaders filter has a contentSecurityPolicy property: this is deprecated in 2.7.0. contentSecurityPolicy has been changed from default-src 'self' to null – the default setting of null means that a Content-Security-Policy header will not be added to HTTP responses from the SecurityHeaders filter. Please use the new CSPFilter to enable CSP functionality.

If play.filters.headers.contentSecurityPolicy is not null, you will receive a warning. It is technically possible to have contentSecurityPolicy and the new CSPFilter active at the same time, but this is not recommended.

You can enable the new CSPFilter by adding it to the play.filters.enabled property:

play.filters.enabled += play.filters.csp.CSPFilter

Note: You will want to review the Content Security Policy closely to ensure it meets your needs. The new CSPFilter is notably more permissive than default-src ‘self’, and is based off the Google Strict CSP configuration. You can use the report-only functionality with a CSP report controller to review policy violations.

Please see the documentation in CSPFilter for more information.

With Play 2.6 the SameSite cookie attribute was enabled for session and flash by default.
The same is true for the CSRF and the language cookie starting with Play 2.7. By default, the SameSite attribute of the CSRF cookie will have the same value like the session cookie has and the language cookie will use SameSite=Lax by default.
You can tweak this using configuration. For example:

play.filters.csrf.cookie.sameSite = null // no same-site for csrf cookie
play.i18n.langCookieSameSite = "strict" // strict same-site for language cookie

§Defaults changes

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

§application/javascript as default content type for JavaScript

application/javascript is now the default content-type returned for JavaScript instead of text/javascript. For generated <script> tags, we are now also omitting the type attribute. See more details about omitting type attribute at the HTML 5 specification.

§Change in self-signed HTTPS certificate

It is now generated under target/dev-mode/generated.keystore instead of directly on the root folder.

§Change in default character set on text/plain Content Types

The Text and Tolerant Text body parsers now use US-ASCII as the default charset, replacing the previous default of ISO-8859-1.

This is because of some newer HTTP standards, specifically RFC 7231, appendix B, which states “The default charset of ISO-8859-1 for text media types has been removed; the default is now whatever the media type definition says.” The text/plain media type definition is defined by RFC 6657, section 4, which specifies US-ASCII. The Text and Tolerant Text Body parsers use text/plain as the content type, so now default appropriately.

§Updated libraries

This section lists significant updates made to our dependencies.

§Akka update

Play 2.7 uses the latest version of Akka 2.5 series. Mixing versions of Akka libraries is not allowed and the newest versions log a warning when they detect that multiple versions of Akka artifacts are being used. You see something like:

Detected possible incompatible versions on the classpath. Please note that a given Akka version MUST be the same across all modules of Akka that you are using, e.g. if you use [2.5.19] all other modules that are released together MUST be of the same version. Make sure you're using a compatible set of libraries. Possibly conflicting versions [2.5.4, 2.5.19] in libraries [akka-actor:2.5.19, akka-remote:2.5.4]

In this example, the fix would be to update akka-remote to the same version Play is using, e.g.:

val AkkaVersion = "2.5.19" // should match the version used by Play

libraryDependencies += "com.typesafe.akka" %% "akka-remote" % AkkaVersion

If your application is using a version that is newer than the one used by Play, you can update the Akka version in your build.sbt file.

§HikariCP update

HikariCP was updated to the latest version which finally removed the configuration initializationFailFast, replaced by initializationFailTimeout. See HikariCP changelog and documentation for initializationFailTimeout to better understand how to use this configuration.

§Guava version updated to 27.0-jre

Play 2.6.x provided 23.0 version of Guava library. Now it is updated to last actual version, 27.0-jre. Lots of changes were made in the library, and you can see the full changelog here.

§specs2 updated to 4.3.5

The previous version was 3.8.x. There are many changes and improvements, so we recommend that you read the release notes for the recent versions of Specs2. The used version updated the Mockito version used to 2.18.x, so we also have updated it.

§Jackson updated to 2.9

Jackson version was updated from 2.8 to 2.9. The release notes for this version are here. It is a release that keeps compatibility, so your application should not be affected. But you may be interested in the new features.

§Hibernate Validator updated to 6.0

Hibernate Validator was updated to version 6.0 which is now compatible with Bean Validation 2.0. See what is new here or read this detailed blog post about the new version.

Note: Keep in mind that this version may not be fully compatible with other Hibernate dependencies you may have in your project. For example, if you are using hibernate-jpamodelgen it is required that you use the latest version to ensure everything will work together:

// Visit to see the list of versions available
libraryDependencies += "org.hibernate" % "hibernate-jpamodelgen" % "5.3.7.Final" % "provided"

§Removed libraries

To make the default play distribution a bit smaller we removed some libraries. The following libraries are no longer dependencies in Play 2.7, so you will need to add them manually to your build if you use them.

§BoneCP removed

BoneCP is removed. If your application is configured to use BoneCP, you need to switch to HikariCP which is the default JDBC connection pool.

play.db.pool = "default"  # Use the default connection pool provided by the platform (HikariCP)
play.db.pool = "hikaricp" # Use HikariCP

You may need to reconfigure the pool to use HikariCP. For example, if you want to configure the maximum number of connections for HikariCP, it would be as follows.

play.db.prototype.hikaricp.maximumPoolSize = 15

For more details, see JDBC configuration section.

Also, you can use your own pool that implements play.api.db.ConnectionPool by specifying the fully-qualified class name.


§Apache Commons (commons-lang3 and commons-codec)

Play had some internal uses of commons-codec and commons-lang3 if you used it in your project you need to add it to your build.sbt:

// Visit to see the list of versions available
libraryDependencies += "commons-codec" % "commons-codec" % "1.11"

And for commons-lang3:

// Visit to see the list of versions available
libraryDependencies += "org.apache.commons" % "commons-lang3" % "3.8.1"

§Other important changes

§Evolutions comment syntax

Play Evolutions now correctly supports SQL92 comment syntax. This means you can write evolutions using -- at the beginning of a line instead of # wherever you choose. Newly generated evolutions using the Evolutions API will now also use SQL92-style comment syntax in all areas. Documentation has also been updated accordingly to prefer the SQL92 style, though the older comment style is still fully supported.

§Query string parameter binding behaviour changed

§When a param’s value is empty (e.g ?myparam=)

Routes that define query string parameters of the following types:

And that are wrapped in the types below:

Until Play 2.6, such cases did return a 400 Bad Request if a request’s query string parameter is empty (e.g. ?myparam=).
That was because it was not possible to parse any of the above types from an empty String (e.g. in Scala, "".toInt raises an exception, as all other above types do for their parsing methods).

As of Play 2.7 there will be no bad request anymore, but instead None (for Scala’s Option), Optional.empty() (for Java’s Optional) or an empty list will be passed to the action method for such query params.
If a default value is defined (e.g. myparam: Option[Int] ?= Option(123)) that default value will be passed instead of course.

Note: That default value behavior also changed if the above types are not wrapped in an Option, Optional or a list, like myparam: Int ?= 3, which before Play 2.7 would also result in a 400 Bad Request instead of picking up the default value.

§When a param does not exist at all

Routes that define default values for query string parameters which wrap a type in

did not pass that default value to the action method when such a request’s query string parameter does not exist at all. Instead None, Optional.empty() or an empty list was passed.

As of Play 2.7 the default value will now be passed to the action method for such non existing query params.

§multipart/form-data file upload changes

Until Play 2.6 uploading an empty file via the multipart/form-data encoding was treated just like uploading a non-empty file. For obvious reasons however, uploading an empty file doesn’t make a lot of sense, therefore as of Play 2.7 an uploaded empty file will be treated just like no file was uploaded at all.
Hence when retrieving an uploaded file via the Scala API or the Java API it will never be empty.

Note: The same logic applies if the filename header of a multipart/form-data file upload part is empty - even when the file itself would not empty.

Next: Java Http.Context changes