play2.x第二课

1、controllers

从IDEA初始化给的play2,x的模板中给的三个controllers:

AsyncController、HomeController、CountController

package controllers
import play.api.mvc._
/**
 * This controller creates an `Action` that demonstrates how to write
 * simple asynchronous code in a controller. It uses a timer to
 * asynchronously delay sending a response for 1 second.
 *
 * @param cc standard controller components
 * @param actorSystem We need the `ActorSystem`'s `Scheduler` to
 * run code after a delay.
 * @param exec We need an `ExecutionContext` to execute our
 * asynchronous code.  When rendering content, you should use Play's
 * default execution context, which is dependency injected.  If you are
 * using blocking operations, such as database or network access, then you should
 * use a different custom execution context that has a thread pool configured for
 * a blocking API.
 */
@Singleton
class AsyncController @Inject()(cc: ControllerComponents, actorSystem: ActorSystem)(implicit exec: ExecutionContext) extends AbstractController(cc) {

  /**
   * Creates an Action that returns a plain text message after a delay
   * of 1 second.
   *
   * The configuration in the `routes` file means that this method
   * will be called when the application receives a `GET` request with
   * a path of `/message`.
   */
  def message = Action.async {
    getFutureMessage(1.second).map { msg => Ok(msg) }
  }

  private def getFutureMessage(delayTime: FiniteDuration): Future[String] = {
    val promise: Promise[String] = Promise[String]()
    actorSystem.scheduler.scheduleOnce(delayTime) {
      promise.success("Hi!")
    }(actorSystem.dispatcher) // run scheduled tasks using the actor system's dispatcher
    promise.future
  }
}

package controllers

import javax.inject._

import play.api.mvc._

/**
 * This controller demonstrates how to use dependency injection to
 * bind a component into a controller class. The class creates an
 * `Action` that shows an incrementing count to users. The [[Counter]]
 * object is injected by the Guice dependency injection system.
 */
@Singleton
class CountController @Inject() (cc: ControllerComponents,
                                 counter: Counter) extends AbstractController(cc) {


  /**
   * Create an action that responds with the [[Counter]]'s current
   * count. The result is plain text. This `Action` is mapped to
   * `GET /count` requests by an entry in the `routes` config file.
   */
  def count = Action { Ok(counter.nextCount().toString) }

}

package controllers

import javax.inject._
import play.api.mvc._

/**
 * This controller creates an `Action` to handle HTTP requests to the
 * application's home page.
 */
//@Singleton和@Inject()是DI(Dependency Injection，即依赖注入)注解。@Singleton注解告诉DI容器该类全局只能有一个实例，
// @Inject()注解告诉DI容器，在该类初始化时注入右侧声明的参数cc。@extends关键字指明HomeController继承自AbstractController。
// AbstractController定义了一些常用方法，例如Action、Ok等等。
//常见Result类型
@Singleton
class HomeController @Inject()(cc: ControllerComponents) extends AbstractController(cc) {

  /**
   * Create an Action to render an HTML page with a welcome message.
   * The configuration in the `routes` file means that this method
   * will be called when the application receives a `GET` request with
   * a path of `/`.
   */
  def index = Action {
    Ok(views.html.index("Your new application is ready."))
  }
}

从这三个controller来明白需要相关的依赖注入和调用views包内的html的相关方法，并且还有相关的ActorSystem的存在，还有OK、Action就是常见的Result的类型等等。。。。

@Singleton和@Inject()

views.html.index

2、相关的控制器的改变

AbstractController和ControllerComponents相关的

3、html必须声明，即必须在html的第一行什么变量@（m:String）

 ! @7gagcp0dh - Internal server error, for (GET) [/] ->
 
play.sbt.PlayExceptions$CompilationException: Compilation error[Cannot write an instance of views.html.client.type to HTTP response. Try to define a Writeable[views.html.client.type]]

 

 

controller调用了html的时候要views.html.sc("类似标题的的名字")