Is each Play framework web request handled with a new dependency injected controller instance, but then what about static controller methods?
<p>My questions are about the lifecycle of controllers in the Play framework for Java, if the controllers are stateful instances or stateless with static methods, and how to use dependency  injection in the controller code.</p>

<p>Is each web request handled by a new instance of a Play controller class, i.e. can a controller store state in fields such as services injected into the controller constructor?
(where in the documentation is it explained?)</p>

<p>Has the Play framework changed since earlier versions (and if so, at what version?) regarding if controllers are stateful instances or stateless controllers with static methods?</p>

<p>Where can you see code examples about how the framework injects services into a controller instance when stateful controller is used and example of how to inject services into a static controller method?</p>

<p>Regarding the latter, i.e. injection into a static method I suppose that would either have to be a parameter to the method which the frameworks will add, or if not possible you maybe instead will have to use a service locator from within the method e.g. instantiate a Guice module class and then use "injector.getInstance" from within the static controller method.</p>

<p>This subject is touched in the section "Dependency injecting controllers" at the following page:</p>

<p><a href="https://www.playframework.com/documentation/2.4.x/JavaDependencyInjection" rel="noreferrer">https://www.playframework.com/documentation/2.4.x/JavaDependencyInjection</a></p>

<p>However, it does not show with code how to actually inject services into a controller instance (but probably the same way as other "components" i.e. with @Inject annotation) and certainly it does not currently show how to use DI with a static controller method.</p>

<p>I am confused about these things because I have not found documentation being clear about my questions, and I have also read in a Play book (from 2013) that the controller methods should be programmed as stateless and the controller methods should be static.</p>

<p>However, when now using activator for generating a Play application for Java with the latest Play version (2.4.6) I can see that the generated Controller method (Application.index) is NOT static.
Also, at the following documentation page, the controller method is NOT static:
<a href="https://www.playframework.com/documentation/2.4.x/JavaActions" rel="noreferrer">https://www.playframework.com/documentation/2.4.x/JavaActions</a></p>

<p>This is confusing, and since it is VERY fundamental to understand whether or not each request is handled by a Controller instance or not (i.e. if state can be used) I think this should be better documented at the page about Controller/Actions than the current documentation (the above linked page) which is not explaining it.</p>

<p>The documentation about dependency injection touches the subject about static and non-static methods at the section "Dependency injecting controllers" mentioning "static routes generator" but I think it should be better explained including code examples.</p>

<p>If someone in the Play team is reading this question, then please add some information to the above linked pages, for example please do mention (if my understanding is correct) that in previous versions of Play the controller methods were static and for those versions you should never store state in fields, but in later versions (beginning from version x?) each request is handled by an instance of a controller and can therefore use state (e.g. constructor parameters injected by the framework).</p>

<p>Please also provide code examples about injection used with static controller methods and injection into stateful controller instances with one instance per request.</p>

<p>The section "Component lifecycle" in the dependency injection page only mentions "components" but I think it should also be explicit about the controller lifecycle and its injection, since it is such a fundamental and important knowledge to communicate clearly to all developers to avoid bugs caused by misunderstandings about being stateful or not.</p>