examples: add kotlin and kotlin android examples (#4037)

Add kotlin version of HelloWorldClient and HelloWorldServer.
Add kotlin version of android example.

RELEASING.md

@@ -72,6 +72,8 @@ $ VERSION_FILES=(
   examples/android/clientcache/app/build.gradle
   examples/android/helloworld/app/build.gradle
   examples/android/routeguide/app/build.gradle
+  examples/example-kotlin/build.gradle
+  examples/example-kotlin/android/helloworld/app/build.gradle
   )
 ```
 

buildscripts/kokoro/android.sh

@@ -44,6 +44,8 @@ cd ../routeguide
 cd ../helloworld
 ./gradlew build
 
+cd $BASE_DIR/github/grpc-java/examples/example-kotlin/android/helloworld/
+./gradlew build
 
 # Skip APK size and dex count comparisons for non-PR builds
 

buildscripts/kokoro/unix.sh

@@ -56,11 +56,18 @@ fi
 
 # Run tests
 ./gradlew build $GRADLE_FLAGS
+./gradlew install
+
 pushd examples
 ./gradlew build $GRADLE_FLAGS
 # --batch-mode reduces log spam
 mvn verify --batch-mode
 popd
+
+pushd examples/example-kotlin/
+./gradlew build $GRADLE_FLAGS
+popd
+
 # TODO(zpencer): also build the GAE examples
 
 LOCAL_MVN_TEMP=$(mktemp -d)

examples/example-kotlin/README.md

@@ -0,0 +1,59 @@
+grpc Kotlin example
+==============================================
+
+The examples require grpc-java to already be built. You are strongly encouraged
+to check out a git release tag, since there will already be a build of grpc
+available. Otherwise you must follow COMPILING.md.
+
+You may want to read through the
+[Quick Start Guide](https://grpc.io/docs/quickstart/java.html)
+before trying out the examples.
+
+To build the examples, run in this directory:
+
+```
+$ ./gradlew installDist
+```
+
+This creates the scripts `hello-world-server`, `hello-world-client`,
+`route-guide-server`, and `route-guide-client` in the
+`build/install/examples/bin/` directory that run the examples. Each
+example requires the server to be running before starting the client.
+
+For example, to try the hello world example first run:
+
+```
+$ ./build/install/examples/bin/hello-world-server
+```
+
+And in a different terminal window run:
+
+```
+$ ./build/install/examples/bin/hello-world-client
+```
+
+That's it!
+
+Please refer to gRPC Java's [README](../README.md) and
+[tutorial](https://grpc.io/docs/tutorials/basic/java.html) for more
+information.
+
+Unit test examples
+==============================================
+
+Examples for unit testing gRPC clients and servers are located in [./src/test](./src/test).
+
+In general, we DO NOT allow overriding the client stub.
+We encourage users to leverage `InProcessTransport` as demonstrated in the examples to
+write unit tests. `InProcessTransport` is light-weight and runs the server
+and client in the same process without any socket/TCP connection.
+
+For testing a gRPC client, create the client with a real stub
+using an InProcessChannelBuilder.java and test it against an InProcessServer.java
+with a mock/fake service implementation.
+
+For testing a gRPC server, create the server as an InProcessServer,
+and test it against a real client stub with an InProcessChannel.
+
+The gRPC-java library also provides a JUnit rule, GrpcServerRule.java, to do the starting
+up and shutting down boilerplate for you.

examples/example-kotlin/android/helloworld/app/build.gradle

@@ -0,0 +1,91 @@
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
+apply plugin: 'com.google.protobuf'
+
+android {
+    compileSdkVersion 27
+
+    defaultConfig {
+        applicationId "io.grpc.helloworldexample"
+        // API level 14+ is required for TLS since Google Play Services v10.2
+        minSdkVersion 14
+        targetSdkVersion 27
+        versionCode 1
+        versionName "1.0"
+    }
+    buildTypes {
+        debug {
+            minifyEnabled false
+        }
+        release {
+            minifyEnabled true
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+    lintOptions {
+        disable 'GoogleAppIndexingWarning', 'HardcodedText', 'InvalidPackage'
+        textReport true
+        textOutput "stdout"
+    }
+    // Android Studio 3.1 does not automatically pick up '<src_set>/kotlin' as source input
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+        main.java.srcDirs += 'src/test/kotlin'
+        androidTest.java.srcDirs += 'src/androidTest/kotlin'
+    }
+
+    lintOptions {
+        // Do not complain about outdated deps, so that this can javax.annotation-api can be same
+        // as other projects in this repo. Your project is not required to do this, and can
+        // upgrade the dep.
+        disable 'GradleDependency'
+        // The Android linter does not correctly detect resources used in Kotlin.
+        // See:
+        //   - https://youtrack.jetbrains.com/issue/KT-7729
+        //   - https://youtrack.jetbrains.com/issue/KT-12499
+        disable 'UnusedResources'
+        textReport true
+        textOutput "stdout"
+    }
+}
+
+protobuf {
+    protoc {
+        artifact = 'com.google.protobuf:protoc:3.5.1-1'
+    }
+    plugins {
+        javalite {
+            artifact = "com.google.protobuf:protoc-gen-javalite:3.0.0"
+        }
+        grpc {
+            artifact = 'io.grpc:protoc-gen-grpc-java:1.13.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+        }
+    }
+    generateProtoTasks {
+        all().each { task ->
+            task.plugins {
+                javalite {}
+                grpc {
+                    // Options added to --grpc_out
+                    option 'lite'
+                }
+            }
+        }
+    }
+}
+
+dependencies {
+    compile 'com.android.support:appcompat-v7:27.0.2'
+    compile 'javax.annotation:javax.annotation-api:1.2'
+    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+
+    // You need to build grpc-java to obtain these libraries below.
+    compile 'io.grpc:grpc-okhttp:1.13.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    compile 'io.grpc:grpc-protobuf-lite:1.13.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    compile 'io.grpc:grpc-stub:1.13.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+}
+
+repositories {
+    mavenCentral()
+}

examples/example-kotlin/android/helloworld/app/proguard-rules.pro

@@ -0,0 +1,17 @@
+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in $ANDROID_HOME/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the proguardFiles
+# directive in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# Add any project specific keep options here:
+
+-dontwarn com.google.common.**
+# Ignores: can't find referenced class javax.lang.model.element.Modifier
+-dontwarn com.google.errorprone.annotations.**
+-dontwarn javax.naming.**
+-dontwarn okio.**
+-dontwarn sun.misc.Unsafe

examples/example-kotlin/android/helloworld/app/src/main/AndroidManifest.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="io.grpc.helloworldexample" >
+
+    <uses-permission android:name="android.permission.INTERNET" />
+
+    <application
+        android:allowBackup="false"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:theme="@style/Base.V7.Theme.AppCompat.Light" >
+        <activity
+            android:name=".HelloworldActivity"
+            android:label="@string/app_name" >
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

examples/example-kotlin/android/helloworld/app/src/main/kotlin/io/grpc/helloworldexample/HelloworldActivity.kt

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2015, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.helloworldexample
+
+import android.app.Activity
+import android.content.Context
+import android.os.AsyncTask
+import android.os.Bundle
+import android.support.v7.app.AppCompatActivity
+import android.text.TextUtils
+import android.text.method.ScrollingMovementMethod
+import android.view.View
+import android.view.inputmethod.InputMethodManager
+import android.widget.Button
+import android.widget.TextView
+import io.grpc.ManagedChannel
+import io.grpc.ManagedChannelBuilder
+import io.grpc.examples.helloworld.GreeterGrpc
+import io.grpc.examples.helloworld.HelloRequest
+import java.io.PrintWriter
+import java.io.StringWriter
+import java.lang.ref.WeakReference
+import java.util.concurrent.TimeUnit
+import kotlinx.android.synthetic.main.activity_helloworld.*
+
+class HelloworldActivity : AppCompatActivity(), View.OnClickListener {
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    setContentView(R.layout.activity_helloworld)
+    grpc_response_text!!.movementMethod = ScrollingMovementMethod()
+    send_button!!.setOnClickListener(this)
+  }
+
+  override fun onClick(view: View) {
+    (getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager)
+        .hideSoftInputFromWindow(host_edit_text!!.windowToken, 0)
+    send_button!!.isEnabled = false
+    grpc_response_text!!.text = ""
+    GrpcTask(this)
+        .execute(
+            host_edit_text!!.text.toString(),
+            message_edit_text!!.text.toString(),
+            port_edit_text!!.text.toString())
+  }
+
+  private class GrpcTask constructor(activity: Activity) : AsyncTask<String, Void, String>() {
+    private val activityReference: WeakReference<Activity> = WeakReference(activity)
+    private var channel: ManagedChannel? = null
+
+    override fun doInBackground(vararg params: String): String {
+      val host = params[0]
+      val message = params[1]
+      val portStr = params[2]
+      val port = if (TextUtils.isEmpty(portStr)) 0 else Integer.valueOf(portStr)
+      return try {
+        channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext().build()
+        val stub = GreeterGrpc.newBlockingStub(channel)
+        val request = HelloRequest.newBuilder().setName(message).build()
+        val reply = stub.sayHello(request)
+        reply.message
+      } catch (e: Exception) {
+        val sw = StringWriter()
+        val pw = PrintWriter(sw)
+        e.printStackTrace(pw)
+        pw.flush()
+
+        "Failed... : %s".format(sw)
+      }
+    }
+
+    override fun onPostExecute(result: String) {
+      try {
+        channel?.shutdown()?.awaitTermination(1, TimeUnit.SECONDS)
+      } catch (e: InterruptedException) {
+        Thread.currentThread().interrupt()
+      }
+
+      val activity = activityReference.get() ?: return
+      val resultText: TextView = activity.findViewById(R.id.grpc_response_text)
+      val sendButton: Button = activity.findViewById(R.id.send_button)
+
+      resultText.text = result
+      sendButton.isEnabled = true
+    }
+  }
+}

examples/example-kotlin/android/helloworld/app/src/main/proto/helloworld.proto

@@ -0,0 +1,38 @@
+// Copyright 2015, gRPC Authors
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+//     http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "io.grpc.examples.helloworld";
+option java_outer_classname = "HelloWorldProto";
+option objc_class_prefix = "HLW";
+
+package helloworld;
+
+// The greeting service definition.
+service Greeter {
+  // Sends a greeting
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+  string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+  string message = 1;
+}

examples/example-kotlin/android/helloworld/app/src/main/res/layout/activity_helloworld.xml

@@ -0,0 +1,54 @@
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
+              android:layout_height="match_parent"
+              tools:context=".MainActivity"
+              android:orientation="vertical" >
+
+    <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal">
+        <EditText
+                android:id="@+id/host_edit_text"
+                android:layout_weight="2"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:hint="Enter Host" />
+        <EditText
+                android:id="@+id/port_edit_text"
+                android:layout_weight="1"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:inputType="numberDecimal"
+                android:hint="Enter Port" />
+    </LinearLayout>
+
+
+    <EditText
+            android:id="@+id/message_edit_text"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:hint="Enter message to send" />
+
+    <Button
+            android:id="@+id/send_button"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="Send Grpc Request" />
+
+    <TextView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:paddingTop="12dp"
+            android:paddingBottom="12dp"
+            android:textSize="16sp"
+            android:text="Response:" />
+
+    <TextView
+            android:id="@+id/grpc_response_text"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:scrollbars = "vertical"
+            android:textSize="16sp" />
+
+</LinearLayout>

examples/example-kotlin/android/helloworld/app/src/main/res/values/strings.xml

@@ -0,0 +1,3 @@
+<resources>
+    <string name="app_name">GrpcHelloworldExample</string>
+</resources>

examples/example-kotlin/android/helloworld/build.gradle

@@ -0,0 +1,27 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+
+buildscript {
+    ext.kotlin_version = '1.2.21'
+
+    repositories {
+        google()
+        jcenter()
+        mavenLocal()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:3.0.1'
+        classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.5"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+        mavenLocal()
+    }
+}

examples/example-kotlin/android/helloworld/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3-bin.zip

examples/example-kotlin/android/helloworld/gradlew

@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

examples/example-kotlin/android/helloworld/gradlew.bat

@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

examples/example-kotlin/android/helloworld/settings.gradle

@@ -0,0 +1 @@
+include ':app'

examples/example-kotlin/build.gradle

@@ -0,0 +1,88 @@
+apply plugin: 'kotlin'
+apply plugin: 'com.google.protobuf'
+
+// Generate IntelliJ IDEA's .idea & .iml project files
+// Starting with 0.8.4 of protobuf-gradle-plugin, *.proto and the gen output files are added
+// to IntelliJ as sources. It is no longer necessary to add them manually to the idea {} block
+// to jump to definitions from Java and Kotlin files.
+// For best results, install the Protobuf and Kotlin plugins for IntelliJ.
+apply plugin: 'idea'
+
+// Provide convenience executables for trying out the examples.
+apply plugin: 'application'
+
+
+buildscript {
+  ext.kotlin_version = '1.2.21'
+
+  repositories {
+    mavenCentral()
+    mavenLocal()
+  }
+  dependencies {
+    classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.5'
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+  }
+}
+
+repositories {
+  mavenCentral()
+  mavenLocal()
+}
+
+// IMPORTANT: You probably want the non-SNAPSHOT version of gRPC. Make sure you
+// are looking at a tagged version of the example and not "master"!
+
+// Feel free to delete the comment at the next line. It is just for safely
+// updating the version in our release process.
+def grpcVersion = '1.13.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+
+dependencies {
+  compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+  compile "com.google.api.grpc:proto-google-common-protos:1.0.0"
+  compile "io.grpc:grpc-netty:${grpcVersion}"
+  compile "io.grpc:grpc-protobuf:${grpcVersion}"
+  compile "io.grpc:grpc-stub:${grpcVersion}"
+
+  testCompile "io.grpc:grpc-testing:${grpcVersion}" // gRCP testing utilities
+  testCompile "junit:junit:4.12"
+  testCompile "org.mockito:mockito-core:1.9.5"
+}
+
+protobuf {
+  protoc {
+    artifact = 'com.google.protobuf:protoc:3.5.1-1'
+  }
+  plugins {
+    grpc {
+      artifact = "io.grpc:protoc-gen-grpc-java:${grpcVersion}"
+    }
+  }
+  generateProtoTasks {
+    all()*.plugins {
+      grpc {}
+    }
+  }
+}
+
+startScripts.enabled = false
+
+task helloWorldServer(type: CreateStartScripts) {
+  mainClassName = 'io.grpc.examples.helloworld.HelloWorldServer'
+  applicationName = 'hello-world-server'
+  outputDir = new File(project.buildDir, 'tmp')
+  classpath = jar.outputs.files + project.configurations.runtime
+}
+
+task helloWorldClient(type: CreateStartScripts) {
+  mainClassName = 'io.grpc.examples.helloworld.HelloWorldClient'
+  applicationName = 'hello-world-client'
+  outputDir = new File(project.buildDir, 'tmp')
+  classpath = jar.outputs.files + project.configurations.runtime
+}
+
+applicationDistribution.into('bin') {
+  from(helloWorldServer)
+  from(helloWorldClient)
+  fileMode = 0755
+}

examples/example-kotlin/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3-bin.zip

examples/example-kotlin/gradlew

@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

examples/example-kotlin/gradlew.bat

@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

examples/example-kotlin/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'examples'

examples/example-kotlin/src/main/kotlin/io/grpc/examples/helloworld/HelloWorldClient.kt

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2015, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.examples.helloworld
+
+import io.grpc.ManagedChannel
+import io.grpc.ManagedChannelBuilder
+import io.grpc.StatusRuntimeException
+import java.util.concurrent.TimeUnit
+import java.util.logging.Level
+import java.util.logging.Logger
+
+/**
+ * A simple client that requests a greeting from the [HelloWorldServer].
+ */
+class HelloWorldClient
+/** Construct client for accessing RouteGuide server using the existing channel.  */
+internal constructor(private val channel: ManagedChannel) {
+    private val blockingStub: GreeterGrpc.GreeterBlockingStub
+            = GreeterGrpc.newBlockingStub(channel)
+
+    /** Construct client connecting to HelloWorld server at `host:port`.  */
+    constructor(host: String, port: Int) : this(ManagedChannelBuilder.forAddress(host, port)
+            // Channels are secure by default (via SSL/TLS). For the example we disable TLS to avoid
+            // needing certificates.
+            .usePlaintext()
+            .build()) {
+    }
+
+
+    @Throws(InterruptedException::class)
+    fun shutdown() {
+        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS)
+    }
+
+    /** Say hello to server.  */
+    fun greet(name: String) {
+        logger.log(Level.INFO, "Will try to greet {0}...", name)
+        val request = HelloRequest.newBuilder().setName(name).build()
+        val response: HelloReply =  try {
+            blockingStub.sayHello(request)
+        } catch (e: StatusRuntimeException) {
+            logger.log(Level.WARNING, "RPC failed: {0}", e.status)
+            return
+        }
+
+        logger.info("Greeting: ${response.message}")
+    }
+
+    companion object {
+        private val logger = Logger.getLogger(HelloWorldClient::class.java.name)
+
+        /**
+         * Greet server. If provided, the first element of `args` is the name to use in the
+         * greeting.
+         */
+        @Throws(Exception::class)
+        @JvmStatic
+        fun main(args: Array<String>) {
+            val client = HelloWorldClient("localhost", 50051)
+            try {
+                /* Access a service running on the local machine on port 50051 */
+                val user = if (args.size > 0) "world" else "world"
+                client.greet(user)
+            } finally {
+                client.shutdown()
+            }
+        }
+    }
+}

examples/example-kotlin/src/main/kotlin/io/grpc/examples/helloworld/HelloWorldServer.kt

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2015, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.examples.helloworld
+
+import io.grpc.Server
+import io.grpc.ServerBuilder
+import io.grpc.stub.StreamObserver
+import java.io.IOException
+import java.util.logging.Level
+import java.util.logging.Logger
+
+/**
+ * Server that manages startup/shutdown of a `Greeter` server.
+ *
+ * Note: this file was automatically converted from Java
+ */
+class HelloWorldServer {
+
+    private var server: Server? = null
+
+    @Throws(IOException::class)
+    private fun start() {
+        /* The port on which the server should run */
+        val port = 50051
+        server = ServerBuilder.forPort(port)
+                .addService(GreeterImpl())
+                .build()
+                .start()
+        logger.log(Level.INFO, "Server started, listening on {0}", port)
+        Runtime.getRuntime().addShutdownHook(object : Thread() {
+            override fun run() {
+                // Use stderr here since the logger may have been reset by its JVM shutdown hook.
+                System.err.println("*** shutting down gRPC server since JVM is shutting down")
+                this@HelloWorldServer.stop()
+                System.err.println("*** server shut down")
+            }
+        })
+    }
+
+    private fun stop() {
+        server?.shutdown()
+    }
+
+    /**
+     * Await termination on the main thread since the grpc library uses daemon threads.
+     */
+    @Throws(InterruptedException::class)
+    private fun blockUntilShutdown() {
+        server?.awaitTermination()
+    }
+
+    internal class GreeterImpl : GreeterGrpc.GreeterImplBase() {
+
+        override fun sayHello(req: HelloRequest, responseObserver: StreamObserver<HelloReply>) {
+            val reply = HelloReply.newBuilder().setMessage("Hello ${req.name}").build()
+            responseObserver.onNext(reply)
+            responseObserver.onCompleted()
+        }
+    }
+
+    companion object {
+        private val logger = Logger.getLogger(HelloWorldServer::class.java.name)
+
+        /**
+         * Main launches the server from the command line.
+         */
+        @Throws(IOException::class, InterruptedException::class)
+        @JvmStatic
+        fun main(args: Array<String>) {
+            val server = HelloWorldServer()
+            server.start()
+            server.blockUntilShutdown()
+        }
+    }
+}

examples/example-kotlin/src/main/proto/helloworld.proto

@@ -0,0 +1,38 @@
+// Copyright 2015, gRPC Authors
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+//     http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "io.grpc.examples.helloworld";
+option java_outer_classname = "HelloWorldProto";
+option objc_class_prefix = "HLW";
+
+package helloworld;
+
+// The greeting service definition.
+service Greeter {
+  // Sends a greeting
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+  string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+  string message = 1;
+}

examples/example-kotlin/src/test/kotlin/io/grpc/examples/helloworld/HelloWorldClientTest.kt

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2015, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.examples.helloworld
+
+import org.junit.Assert.assertEquals
+import org.mockito.AdditionalAnswers.delegatesTo
+import org.mockito.Mockito.mock
+import org.mockito.Mockito.verify
+
+import io.grpc.stub.StreamObserver
+import io.grpc.testing.GrpcServerRule
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.mockito.ArgumentCaptor
+import org.mockito.Matchers
+
+/**
+ * Unit tests for [HelloWorldClient].
+ * For demonstrating how to write gRPC unit test only.
+ * Not intended to provide a high code coverage or to test every major usecase.
+ *
+ *
+ * For more unit test examples see [io.grpc.examples.routeguide.RouteGuideClientTest] and
+ * [io.grpc.examples.routeguide.RouteGuideServerTest].
+ */
+@RunWith(JUnit4::class)
+class HelloWorldClientTest {
+    /**
+     * This creates and starts an in-process server, and creates a client with an in-process channel.
+     * When the test is done, it also shuts down the in-process client and server.
+     */
+    @get:Rule
+    val grpcServerRule = GrpcServerRule().directExecutor()
+
+    private val serviceImpl = mock(GreeterGrpc.GreeterImplBase::class.java, delegatesTo<Any>(object : GreeterGrpc.GreeterImplBase() {
+
+    }))
+    private var client: HelloWorldClient? = null
+
+    @Before
+    @Throws(Exception::class)
+    fun setUp() {
+        // Add service.
+        grpcServerRule.serviceRegistry.addService(serviceImpl)
+        // Create a HelloWorldClient using the in-process channel;
+        client = HelloWorldClient(grpcServerRule.channel)
+    }
+
+    /**
+     * To test the client, call from the client against the fake server, and verify behaviors or state
+     * changes from the server side.
+     */
+    @Test
+    fun greet_messageDeliveredToServer() {
+        val requestCaptor = ArgumentCaptor.forClass(HelloRequest::class.java)
+        val testName = "test name"
+
+        client!!.greet(testName)
+
+        verify<GreeterGrpc.GreeterImplBase>(serviceImpl)
+                .sayHello(requestCaptor.capture(), Matchers.any<StreamObserver<HelloReply>>())
+        assertEquals(testName, requestCaptor.value.name)
+    }
+}

examples/example-kotlin/src/test/kotlin/io/grpc/examples/helloworld/HelloWorldServerTest.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2016, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.examples.helloworld
+
+import org.junit.Assert.assertEquals
+
+import io.grpc.examples.helloworld.HelloWorldServer.GreeterImpl
+import io.grpc.testing.GrpcServerRule
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+/**
+ * Unit tests for [HelloWorldServer].
+ * For demonstrating how to write gRPC unit test only.
+ * Not intended to provide a high code coverage or to test every major usecase.
+ *
+ *
+ * For more unit test examples see [io.grpc.examples.routeguide.RouteGuideClientTest] and
+ * [io.grpc.examples.routeguide.RouteGuideServerTest].
+ */
+@RunWith(JUnit4::class)
+class HelloWorldServerTest {
+    /**
+     * This creates and starts an in-process server, and creates a client with an in-process channel.
+     * When the test is done, it also shuts down the in-process client and server.
+     */
+    @get:Rule
+    val grpcServerRule = GrpcServerRule().directExecutor()
+
+    /**
+     * To test the server, make calls with a real stub using the in-process channel, and verify
+     * behaviors or state changes from the client side.
+     */
+    @Test
+    @Throws(Exception::class)
+    fun greeterImpl_replyMessage() {
+        // Add the service to the in-process server.
+        grpcServerRule.serviceRegistry.addService(GreeterImpl())
+
+        val blockingStub = GreeterGrpc.newBlockingStub(grpcServerRule.channel)
+        val testName = "test name"
+
+        val reply = blockingStub.sayHello(HelloRequest.newBuilder().setName(testName).build())
+
+        assertEquals("Hello $testName", reply.message)
+    }
+}