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play.api.inject

Play's runtime dependency injection abstraction.

Play's runtime dependency injection support is built on JSR-330, which provides a specification for declaring how dependencies get wired to components. JSR-330 however does not address how components are provided to or located by a DI container. Play's API seeks to address this in a DI container agnostic way.

The reason for providing this abstraction is so that Play, the modules it provides, and third party modules can all express their bindings in a way that is not specific to any one DI container.

Components are bound in the DI container. Each binding is identified by a BindingKey, which is typically an interface that the component implements, and may be optionally qualified by a JSR-330 qualifier annotation. A binding key is bound to a BindingTarget, which describes how the implementation of the interface that the binding key represents is constructed or provided. Bindings may also be scoped using JSR-330 scope annotations.

Bindings are provided by instances of Module.

Out of the box, Play provides an implementation of this abstraction using Guice.

Attributes

See also: The Module class for information on how to provide bindings.

Members list

Type members

Classlikes

Application lifecycle register.

This is used to hook into Play lifecycle events, specifically, when Play is stopped. The reason Play only provides lifecycle callbacks for stopping is that constructors are considered the application start callback. This has several advantages:

It simplifies implementation, if you want to start something, just do it in the constructor.
It simplifies state, there's no transitional state where an object has been created but not started yet. Hence, as long as you have a reference to something, it's safe to use it.
It solves startup dependencies in a type safe manner - the order that components must be started is enforced by the order that they must be instantiated due to the component graph.

Stop hooks are executed when the application is shutdown, in reverse from when they were registered. Due to this reverse ordering, a component can know that it is safe to use the components it depends on as long as it hasn't received a shutdown event.

To use this, declare a dependency on ApplicationLifecycle, and then register the stop hook when the component is started. For example:

 import play.api.inject.ApplicationLifecycle
 import javax.inject.Inject

 class SomeDatabase @Inject() (applicationLifecycle: ApplicationLifecycle) {

   private val connectionPool = new SomeConnectionPool()
   applicationLifecycle.addStopHook { () =>
     Future.successful(connectionPool.shutdown())
   }

   ...
 }

Attributes

Supertypes: class Object

trait Matchable

class Any
Known subtypes: class DefaultApplicationLifecycle

A binding.

Bindings are used to bind classes, optionally qualified by a JSR-330 qualifier annotation, to instances, providers or implementation classes.

Bindings may also specify a JSR-330 scope. If, and only if that scope is javax.inject.Singleton, then the binding may declare itself to be eagerly instantiated. In which case, it should be eagerly instantiated when Play starts up.

Value parameters

eager: Whether the binding should be eagerly instantiated.
key: The binding key.
scope: The JSR-330 scope.
source: Where this object was bound. Used in error reporting.
target: The binding target.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: trait Serializable

trait Product

trait Equals

class Object

trait Matchable

class Any
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Constructor for a binding Key that doesn't have a qualifier.

Attributes

See also: The Module class for information on how to provide bindings.
Companion: class
Supertypes: trait Product

trait Mirror

class Object

trait Matchable

class Any
Self type: BindingKey.type

A binding key.

A binding key consists of a class and zero or more JSR-330 qualifiers.

Value parameters

clazz: The class to bind.
qualifier: An optional qualifier.

Attributes

See also: The Module class for information on how to provide bindings.
Companion: object
Supertypes: trait Serializable

trait Product

trait Equals

class Object

trait Matchable

class Any
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A binding target that is provided by another key - essentially an alias.

Attributes

Supertypes: trait Serializable

trait Product

trait Equals

trait BindingTarget[T]

class Object

trait Matchable

class Any
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A binding target.

This trait captures the four possible types of targets.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: class Object

trait Matchable

class Any
Known subtypes: class BindingKeyTarget[T]

class ConstructionTarget[T]

class ProviderConstructionTarget[T]

class ProviderTarget[T]

The Play BuiltinModule.

Provides all the core components of a Play application. This is typically automatically enabled by Play for an application.

Attributes

Supertypes: class SimpleModule

class Module

class Object

trait Matchable

class Any

Attributes

Supertypes: trait Provider[Config]

class Object

trait Matchable

class Any

Attributes

Supertypes: trait Provider[Configuration]

class Object

trait Matchable

class Any

A binding target that is provided by a class.

Attributes

See also: The play.api.inject.Module class for information on how to provide bindings.
Supertypes: trait Serializable

trait Product

trait Equals

trait BindingTarget[T]

class Object

trait Matchable

class Any
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@Singleton

Default implementation of the application lifecycle.

Attributes

Supertypes: trait ApplicationLifecycle

class Object

trait Matchable

class Any

Attributes

Supertypes: trait Provider[Environment]

class Object

trait Matchable

class Any

An injector, capable of providing components.

This is an abstraction over whatever dependency injection is being used in Play. A minimal implementation may only call newInstance on the passed in class.

This abstraction is primarily provided for libraries that want to remain agnostic to the type of dependency injection being used. End users are encouraged to use the facilities provided by the dependency injection framework they are using directly, for example, if using Guice, use com.google.inject.Injector instead of this.

Attributes

Supertypes: class Object

trait Matchable

class Any
Known subtypes: object NewInstanceInjector

class SimpleInjector

A Play dependency injection module.

Dependency injection modules can be used by Play plugins to provide bindings for JSR-330 compliant ApplicationLoaders. Any plugin that wants to provide components that a Play application can use may implement one of these.

Providing custom modules can be done by appending their fully qualified class names to play.modules.enabled in application.conf, for example

 play.modules.enabled += "com.example.FooModule"
 play.modules.enabled += "com.example.BarModule"

It is strongly advised that in addition to providing a module for JSR-330 DI, that plugins also provide a Scala trait that constructs the modules manually. This allows for use of the module without needing a runtime dependency injection provider.

The bind methods are provided only as a DSL for specifying bindings. For example:

 def bindings(env: Environment, conf: Configuration) = Seq(
   bind[Foo].to[FooImpl],
   bind[Bar].to(new Bar()),
   bind[Foo].qualifiedWith[SomeQualifier].to[OtherFoo]
 )

Attributes

Supertypes: class Object

trait Matchable

class Any
Known subtypes: class I18nModule

class SimpleModule

class BuiltinModule

class CookiesModule

class LegacyCookiesModule

class AssetsModule
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Locates and loads modules from the Play environment.

Attributes

Supertypes: class Object

trait Matchable

class Any
Self type: Modules.type

An injector that simply creates a new instance of the passed in classes using the classes no-arg constructor.

Attributes

Supertypes: trait Injector

class Object

trait Matchable

class Any
Self type: NewInstanceInjector.type

A binding target that is provided by a provider class.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: trait Serializable

trait Product

trait Equals

trait BindingTarget[T]

class Object

trait Matchable

class Any
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A binding target that is provided by a provider instance.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: trait Serializable

trait Product

trait Equals

trait BindingTarget[T]

class Object

trait Matchable

class Any
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A qualifier annotation.

Since bindings may specify either annotations, or instances of annotations, this abstraction captures either of those two possibilities.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: class Object

trait Matchable

class Any
Known subtypes: class QualifierClass[T]

class QualifierInstance[T]

A qualifier annotation class.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: trait Serializable

trait Product

trait Equals

trait QualifierAnnotation

class Object

trait Matchable

class Any
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A qualifier annotation instance.

Attributes

See also: The Module class for information on how to provide bindings.
Supertypes: trait Serializable

trait Product

trait Equals

trait QualifierAnnotation

class Object

trait Matchable

class Any
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@Singleton

Attributes

Companion: object
Supertypes: trait Provider[Router]

class Object

trait Matchable

class Any

Attributes

Companion: class
Supertypes: class Object

trait Matchable

class Any
Self type: RoutesProvider.type

A simple map backed injector.

This injector is intended for use by compile time injected applications in the transitional period between when Play fully supports dependency injection across the whole code base, and when some parts of Play still access core components through Play's global state. Since Play's global state requires that some components are still dynamically looked up from an injector, when using a compile time DI approach, there is typically no way to dynamically look up components, so this provides a simple implementation of the Injector trait to allow components that Play requires to be dynamically looked up.

It is intended to just hold built in Play components, but may be used to add additional components by end users when required.

The injector is an immutable structure, new components can be added using the + convenience method, which returns a new injector with that component included.

Value parameters

components: The components that this injector provides.
fallback: The injector to fallback to if no component can be found.

Attributes

Supertypes: trait Injector

class Object

trait Matchable

class Any

A simple Play module, which can be configured by passing a function or a list of bindings.

Attributes

Supertypes: class Module

class Object

trait Matchable

class Any
Known subtypes: class BuiltinModule

class CookiesModule

class LegacyCookiesModule

Value members

Concrete methods

Create a binding key for the given class.

Attributes

See also: The Module class for information on how to provide bindings.

Create a binding key for the given class.

Attributes

See also: The Module class for information on how to provide bindings.

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