如何在Scala中使用Java代理 [英] How to use java proxy in scala

问题描述

我有一个Iface接口，它有两个用Java编写的方法.该接口是Zzz类的内部接口. 我已经在Scala中编写了调用处理程序.然后，我尝试在如下所示的scala中创建一个新的代理实例.

I have an interface as Iface that has two methods written in java. That interface is an inner interface of Zzz class. I have written the invocation handler in scala. Then I tried to create a new proxy instance in scala like below.

 val handler = new ProxyInvocationHandler // this handler implements
                                          //InvocationHandler interface

 val impl = Proxy.newProxyInstance(
  Class.forName(classOf[Iface].getName).getClassLoader(),
  Class.forName(classOf[Iface].getName).getClasses,
  handler
).asInstanceOf[Iface]

但是在这里编译器说

$Proxy0 cannot be cast to xxx.yyy.Zzz$Iface

如何在短时间内通过代理实现此功能.

How can I do this with proxy, in a short way.

推荐答案

这是您代码的固定版本.它还可以编译甚至执行某些操作！

Here is the fixed version of your code. Also it compiles and even does something!

import java.lang.reflect.{Method, InvocationHandler, Proxy}

object ProxyTesting {

  class ProxyInvocationHandler extends InvocationHandler {
    def invoke(proxy: scala.AnyRef, method: Method, args: Array[AnyRef]): AnyRef = {
      println("Hello Stackoverflow when invoking method with name \"%s\"".format(method.getName))
      proxy
    }
  }

  trait Iface {
    def doNothing()
  }

  def main(args: Array[String]) {
    val handler = new ProxyInvocationHandler

    val impl = Proxy.newProxyInstance(
      classOf[Iface].getClassLoader,
      Array(classOf[Iface]),
      handler
    ).asInstanceOf[Iface]

    impl.doNothing()
  }

}

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