Question

我正在玩scala（新手），我正在尝试使用Java 7 NIO（因为我喜欢开始轻松）。但我无法弄清楚如何为接受实例化CompletionHandler。以下代码是错误的，我无法解决它：

package async

import java.nio.channels.AsynchronousServerSocketChannel
import java.net.InetAddress
import java.net.InetSocketAddress
import java.nio.channels.CompletionHandler
import java.nio.channels.AsynchronousSocketChannel

class AsyncServer (port: Int) {

  val socketServer = AsynchronousServerSocketChannel.open();
  socketServer.bind(new InetSocketAddress(port))

  val connectionHandler = new CompletionHandler[AsynchronousSocketChannel, Integer](){

  }

  def init() = socketServer accept(1 ,  connectionHandler)

}

Answer 1

要创建connectHandler实例，您需要实现CompletionHandler方法：

...
val connectionHandler = new CompletionHandler[AsynchronousSocketChannel, Integer] {
  def completed(result: AsynchronousSocketChannel, attachment: Integer ) {}
  def failed(exc: Throwable , attachment: Integer) {}
}
...

并且，因为A中的接口类型是不变的，但是你在A中调用的方法是逆变的：

...
public abstract <A> void accept(A attachment,
                                CompletionHandler<AsynchronousSocketChannel,? super A> handler);
...

你需要强制转换才能进行类型检查：

socketServer accept(1, connectionHandler.asInstanceOf[CompletionHandler[java.nio.channels.AsynchronousSocketChannel, _ >: Any]]

如何在Scala中实例化Java 7完成处理程序

1 个答案: