add dril02 -exercise3

src/main/kotlin/drills/drill02/exercise2/Rev.kt

@@ -1,14 +1,15 @@
 package drills.drill02.exercise2
 
+import java.io.Serializable
 import java.rmi.Remote
 import java.rmi.RemoteException
 import java.rmi.server.UnicastRemoteObject
 
 interface Rev : Remote {
     @Throws(RemoteException::class)
-    fun <T> executeTask(task: () -> T): T
+    fun <T : Serializable> executeTask(task: () -> T): T
 }
 
 class RevImpl : Rev, UnicastRemoteObject() {
-    override fun <T> executeTask(task: () -> T): T = task()
+    override fun <T : Serializable> executeTask(task: () -> T): T = task()
 }

src/main/kotlin/drills/drill02/exercise3/LogHandler.kt

@@ -0,0 +1,11 @@
+package drills.drill02.exercise3
+
+import java.lang.reflect.InvocationHandler
+import java.lang.reflect.Method
+
+class LogHandler(private val target: Any) : InvocationHandler {
+    override fun invoke(proxy: Any?, method: Method?, args: Array<out Any>?): Any {
+        println("log: method '$method' has been invoked")
+        return method?.invoke(target, *(args ?: arrayOf())) ?: Unit
+    }
+}

src/main/kotlin/drills/drill02/exercise3/Main.kt

@@ -0,0 +1,15 @@
+package drills.drill02.exercise3
+
+fun main() {
+    val factory = MathFactory()
+
+    val math = factory.create()
+    val mathLog = factory.create(logger = true)
+
+    println("Enter two numbers:")
+    val a = readLine()?.toFloat() ?: 0f
+    val b = readLine()?.toFloat() ?: 0f
+
+    println("The sum is ${math.add(a, b)}.")
+    println("The sum is ${mathLog.add(a, b)}.")
+}

src/main/kotlin/drills/drill02/exercise3/Math.kt

@@ -0,0 +1,18 @@
+package drills.drill02.exercise3
+
+interface Math {
+    fun add(a: Float, b: Float): Float
+    fun sub(a: Float, b: Float): Float
+    fun mul(a: Float, b: Float): Float
+    fun div(a: Float, b: Float): Float
+}
+
+class MathImpl : Math {
+    override fun add(a: Float, b: Float): Float = a + b
+
+    override fun sub(a: Float, b: Float): Float = a - b
+
+    override fun mul(a: Float, b: Float): Float = a * b
+
+    override fun div(a: Float, b: Float): Float = a / b
+}

src/main/kotlin/drills/drill02/exercise3/MathFactory.kt

@@ -0,0 +1,15 @@
+package drills.drill02.exercise3
+
+import java.lang.reflect.Proxy
+
+class MathFactory {
+    fun create(logger: Boolean = false): Math {
+        return if (logger) {
+            Proxy.newProxyInstance(
+                this::class.java.classLoader,
+                arrayOf(Math::class.java),
+                LogHandler(MathImpl())
+            ) as Math
+        } else MathImpl()
+    }
+}

src/main/kotlin/util/rmi/Client.kt

@@ -20,7 +20,7 @@ class Client(private val handler: () -> Unit) {
     }
 
     companion object {
-        fun lookup(name: String, port: Int = 4242): Remote =
-            Naming.lookup("rmi://localhost:$port/$name")
+        fun lookup(name: String, host: String = "localhost", port: Int = 4242): Remote =
+            Naming.lookup("rmi://$host:$port/$name")
     }
 }