§Writing Play Modules
Note: This page covers the new module system to add new functionality to Play.
The deprecated
play.Pluginsystem is removed as of 2.5.x.
A module can be written using any dependency injection framework. However, when you want to extend Play, you need to avoid dependencies on a specific framework so that your extension can work independently of the dependency injection. Play previously used the play.Plugin system for this purpose, but in 2.5.x, Plugins have been replaced with Play modules.
A Play module is a class that extends play.inject.Module and can be registered with Play without relying explicitly on a particular dependency injection framework. This allows everyone to use Play modules.
A list of Play modules are available in the module directory.
In addition, because Play uses Play modules for built-in functionality, a Play module must be used to replace or augment built-in functionality.
§Creating and migrating Play modules
Creating a Play module is simple:
public class MyApi {}
public class MyModule extends play.inject.Module {
public List<Binding<?>> bindings(Environment environment, Config config) {
return Collections.singletonList(bindClass(MyApi.class).toSelf());
}
}For more information, see the “Create a Module class” section of Plugins to Modules.
§Module registration
By default, Play will load any class called Module that is defined in the root package (the “app” directory) or
you can define them explicitly inside the reference.conf or the application.conf:
play.modules.enabled += "modules.MyModule"
Please see migration page and the dependency injection documentation for more details.
§Application lifecycle
A module can detect when Play shutdown occurs by injecting the play.inject.ApplicationLifecycle interface into the singleton instance and adding a shutdown hook.
Please see the `ApplicationLifecycle` example and ApplicationLifecycle reference for more details.
§Testing Play modules
Play Modules can be tested using Play’s built in test functionality, by using the GuiceApplicationBuilder and adding a binding to the module.
Application application = new GuiceApplicationBuilder().bindings(new MyModule()).build();Please see Testing with Guice for more details.
§Listing existing Play modules
The Modules.locate(env, conf) method will display a list of all available Play modules in an application. There is no corresponding Java class.
§Overriding Built-In Modules
There are some cases where Play provides a built-in module that must be overridden.
For example, WSClient functionality is implemented by the WSClient interface and backed by AhcWSClientProvider. If you write a replacement class MyWSClient that extends WSClient, you can bind it with:
public class MyWSModule extends play.inject.Module {
public List<Binding<?>> bindings(Environment environment, Config config) {
return Collections.singletonList(
bindClass(WSClient.class).toProvider(MyWSClientProvider.class));
}
}§Testing Overrides
Testing the application should be done using the overrides method to replace the existing implementation:
Application application = new GuiceApplicationBuilder().overrides(new MyWSModule()).build();§Registration Overrides
Because the AhcWSModule is loaded automatically in reference.conf, you must first disable the default module before adding the replacement module:
play.modules.disabled += "play.libs.ws.ahc.AhcWSModule"
play.modules.enabled += "modules.MyWSModule"
You should not disable existing modules in reference.conf when publishing a Play module, as it may have unexpected consequences. Please see the migration page for details.