DI Dependency Injection
@Inject 在字段或构造函数上  建议在构造函数上
import javax.inject._

class MyComponent @Inject() (component1: Component1) {
   // ...
}
@Inject 类名之后，构造函数参数之前，且带括号

控制器(Controller）加载
通过routes ，加载控制器，并与URL关联

路由定义 conf/routes
GET    /                 controllers.HomeController.hello
GET    /hello            controllers.HomeController.hello

@Singleton  单例

实现绑定到接口
import com.google.inject.ImplementedBy

@ImplementedBy(classOf[EnglishHello])
trait Hello {
  def sayHello(name: String): String
}

class EnglishHello extends Hello {
  def sayHello(name: String) = "Hello " + name
}

一个特质多个实现  @Named

import com.google.inject.AbstractModule
import com.google.inject.name.Names

class Module extends AbstractModule {
  override def configure() = {
    bind(classOf[Hello])
      .annotatedWith(Names.named("en"))
      .to(classOf[EnglishHello])

    bind(classOf[Hello])
      .annotatedWith(Names.named("de"))
      .to(classOf[GermanHello])
  }
}

Module.scala  工程根目录  Play 自动加载并注册
启动时 初始化
其他名字或其他包  application.conf 配置
play.modules.enabled += "modules.HelloModule"

禁用模块的自动注册
play.modules.disabled += "Module"

注入时 指定 name 
class MyComponent @Inject() (@Name("en") hello: Hello) {
  // ...
}


配置绑定
通过配置 实现具体的绑定
Configuration和ClassLoader

import com.google.inject.AbstractModule
import com.google.inject.name.Names
import play.api.Configuration
import play.api.Environment

class Module(environment: Environment, configuration: Configuration) extends AbstractModule {
  override def configure() = {
    // 配置文件中的配置项格式如下:
    // hello.en = "myapp.EnglishHello"
    // hello.de = "myapp.GermanHello"
    val helloConfiguration: Configuration =
      configuration.getOptional[Configuration]("hello").getOrElse(Configuration.empty)
    val languages: Set[String] = helloConfiguration.subKeys

    for (l <- languages) {
      val bindingClassName: String = helloConfiguration.get[String](l)
      val bindingClass: Class[_ <: Hello] =
        environment.classLoader
          .loadClass(bindingClassName)
          .asSubclass(classOf[Hello])
      bind(classOf[Hello])
        .annotatedWith(Names.named(l))
        .to(bindingClass)
    }
  }
}


 play REST hello 实例    
 sbt 创建运行 Scala play 项目