Ktor to your heart’s content: easy mobile backends in Kotlin

Most Android developers are familiar with Kotlin and use it every day with great success (and joy!). But the bloodline of the language extends well beyond Android! From cross-platform development, to the desktop, to the web, to backends, Kotlin’s pedigree as a versatile language puts all us developers in a great position to leverage existing knowledge for a variety of tasks outside a mobile engineer’s comfort zone. In this session we’ll use Kotlin, Ktor and coroutines to write a backend for our splendid fictional mobile app product: PushBeat.

After learning the basics of a RESTful API, we’ll see what Ktor takes care of for us, what features may be helpful for our mobile projects, and how little we actually need to learn to be a productive backend engineer in no time!

---

The original deck (Keynote 10.0) is available here: https://www.dropbox.com/s/rhohmdi81sxah34/Ktor%20to%20your%20heart%27s%20content.key.zip?dl=0

The recording is here: https://www.youtube.com/watch?v=p8RA-3t0jGA

The sample project is here: https://github.com/rock3r/pushbeat

Transcript

1. Sebastiano Poggi
   @seebrock3r
   Easy mobile backends in Kotlin
   Ktor to your heart’s content
   

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5. REST GraphQL (g)RPC
   

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6. REST GraphQL (g)RPC Firebase
   

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7. REST GraphQL (g)RPC
   • Oldest and simplest of them all
   
   • More of a style than a protocol
   
   • Not a standard, uses standards in the stack
   
   • Basic concepts: methods and resources
   
   • Most widely used of the three
   
   • Available pretty much everywhere
   

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8. REST GraphQL (g)RPC
   • Graph-based API language created by Facebook
   
   • Not a standard, but has OSS specification
   
   • Served over HTTP
   
   • Single endpoint, using a query language
   

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9. REST GraphQL (g)RPC
   • Remote Procedure Call protocol, by Google
   
   • Not a standard, but has OSS specification
   
   • Served over HTTP/2
   
   • Based on protocol buffers (protobuf)
   
   • Generates type-safe client and server bindings
   

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10. REST GraphQL (g)RPC
    What’s the best for you?
    

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11. …it depends!
    REST GraphQL (g)RPC
    What’s the best for you?
    

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12. REST
    • Fully supported by Ktor
    
    • Pragmatic “RESTful enough”
    

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13. Ktor
    

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14. Ktor
    • Kotlin-based framework for async clients and servers
    
    • Familiar language for Android devs
    
    • Easy async support with coroutines
    
    • Unopinionated
    
    • Pick the pieces you need and like
    
    • Testable
    Docs at ktor.io
    

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15. Ktor
    • Covers both servers and clients
    
    • Support for Kotlin/Multiplatform (client)
    
    • Support for REST and WebSockets
    
    • Support for auth: basic, token-based (OAuth)
    Docs at ktor.io
    

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16. Ktor
    • Our example RESTful server
    
    • REST APIs serving JSON
    
    • HTML endpoints
    
    • Authentication
    
    • Running locally and deploying to AppEngine
    Docs at ktor.io
    

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17. PushBeat
    PushBeat
    You seem ver e se
    What about taking a short break
    • Fictional IoT service & Android app
    
    • Track your heartbeat when you push code
    
    • If it’s too high, it suggests you take a break
    Code at github.com/rock3r/pushbeat
    

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18. $ curl https:"#sdk.cloud.google.com | bash
    1
    2
    3
    Set up AppEngine SDK
    1. Install Google Cloud SDK
    2. Create GCP project and enable billing
    

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19. $ cd ~/path/to/project "$ gcloud init
    5. Select your project
    $ gcloud auth login
    $ gcloud components install app-engine-java
    4. Login to GCP
    Set up AppEngine SDK
    3. Install AppEngine Java component
    

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20. build.gradle.kts
    import com.google.cloud.tools.gradle.appengine.standard.AppEngineStandardExtension
    
    import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
    
    plugins {
    
    kotlin("jvm")
    
    kotlin("plugin.serialization") version "1.3.72"
    
    war
    
    }
    
    buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    Set up Ktor and AppEngine
    

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21. import com.google.cloud.tools.gradle.appengine.standard.AppEngineStandardExtension
    
    import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
    
    plugins {
    
    kotlin("jvm")
    
    kotlin("plugin.serialization") version "1.3.72"
    
    war
    
    }
    
    buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    Set up Ktor and AppEngine
    build.gradle.kts
    

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22. import com.google.cloud.tools.gradle.appengine.standard.AppEngineStandardExtension
    
    import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
    
    plugins {
    
    kotlin("jvm")
    
    kotlin("plugin.serialization") version "1.3.72"
    
    war
    
    }
    
    buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    Set up Ktor and AppEngine
    build.gradle.kts
    

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23. import com.google.cloud.tools.gradle.appengine.standard.AppEngineStandardExtension
    
    import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
    
    plugins {
    
    kotlin("jvm")
    
    kotlin("plugin.serialization") version "1.3.72"
    
    war
    
    }
    
    buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    Set up Ktor and AppEngine
    build.gradle.kts
    

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24. appengine { … }
    Groovy DSL:
    import com.google.cloud.tools.gradle.appengine.standard.AppEngineStandardExtension
    
    import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
    
    plugins {
    
    kotlin("jvm")
    
    kotlin("plugin.serialization") version "1.3.72"
    
    war
    
    }
    
    buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    Set up Ktor and AppEngine
    build.gradle.kts
    

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25. import com.google.cloud.tools.gradle.appengine.standard.AppEngineStandardExtension
    
    import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
    
    plugins {
    
    kotlin("jvm")
    
    kotlin("plugin.serialization") version "1.3.72"
    
    war
    
    }
    
    buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    Set up Ktor and AppEngine
    cloud.google.com/sdk/install
    build.gradle.kts
    

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26. buildscript {
    
    repositories {
    
    mavenCentral()
    
    jcenter()
    
    }
    
    dependencies {
    
    classpath("com.google.cloud.tools:appengine-gradle-plugin:2.2.0")
    
    }
    
    }
    
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    implementation(kotlin("stdlib-jdk8"))
    
    implementation("ch.qos.logback:logback-classic:1.2.3")
    
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion")
    
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0")
    
    implementation("io.ktor:ktor-server-servlet:$ktorVersion")
    
    implementation("io.ktor:ktor-html-builder:$ktorVersion")
    
    implementation("io.ktor:ktor-auth:$ktorVersion")
    
    Set up Ktor and AppEngine
    build.gradle.kts
    

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27. "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    implementation(kotlin("stdlib-jdk8"))
    
    implementation("ch.qos.logback:logback-classic:1.2.3")
    
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion")
    
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0")
    
    implementation("io.ktor:ktor-server-servlet:$ktorVersion")
    
    implementation("io.ktor:ktor-html-builder:$ktorVersion")
    
    implementation("io.ktor:ktor-auth:$ktorVersion")
    
    implementation("io.ktor:ktor-locations:$ktorVersion")
    
    implementation("io.ktor:ktor-serialization:$ktorVersion")
    
    implementation("io.ktor:ktor-server-host-common:$ktorVersion")
    
    providedCompile("com.google.appengine:appengine:1.9.60")
    
    testImplementation("io.ktor:ktor-server-tests:$ktorVersion")
    
    }
    Set up Ktor and AppEngine
    build.gradle.kts
    

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28. "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    implementation(kotlin("stdlib-jdk8"))
    
    implementation("ch.qos.logback:logback-classic:1.2.3")
    
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion")
    
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0")
    
    implementation("io.ktor:ktor-server-servlet:$ktorVersion")
    
    implementation("io.ktor:ktor-html-builder:$ktorVersion")
    
    implementation("io.ktor:ktor-auth:$ktorVersion")
    
    implementation("io.ktor:ktor-locations:$ktorVersion")
    
    implementation("io.ktor:ktor-serialization:$ktorVersion")
    
    implementation("io.ktor:ktor-server-host-common:$ktorVersion")
    
    providedCompile("com.google.appengine:appengine:1.9.60")
    
    testImplementation("io.ktor:ktor-server-tests:$ktorVersion")
    
    }
    Set up Ktor and AppEngine
    Features
    build.gradle.kts
    

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29. "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    implementation(kotlin("stdlib-jdk8"))
    
    implementation("ch.qos.logback:logback-classic:1.2.3")
    
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion")
    
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0")
    
    implementation("io.ktor:ktor-server-servlet:$ktorVersion")
    
    implementation("io.ktor:ktor-html-builder:$ktorVersion")
    
    implementation("io.ktor:ktor-auth:$ktorVersion")
    
    implementation("io.ktor:ktor-locations:$ktorVersion")
    
    implementation("io.ktor:ktor-serialization:$ktorVersion")
    
    implementation("io.ktor:ktor-server-host-common:$ktorVersion")
    
    providedCompile("com.google.appengine:appengine:1.9.60")
    
    testImplementation("io.ktor:ktor-server-tests:$ktorVersion")
    
    }
    Set up Ktor and AppEngine
    build.gradle.kts
    

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30. "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    implementation(kotlin("stdlib-jdk8"))
    
    implementation("ch.qos.logback:logback-classic:1.2.3")
    
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion")
    
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0")
    
    implementation("io.ktor:ktor-server-servlet:$ktorVersion")
    
    implementation("io.ktor:ktor-html-builder:$ktorVersion")
    
    implementation("io.ktor:ktor-auth:$ktorVersion")
    
    implementation("io.ktor:ktor-locations:$ktorVersion")
    
    implementation("io.ktor:ktor-serialization:$ktorVersion")
    
    implementation("io.ktor:ktor-server-host-common:$ktorVersion")
    
    providedCompile("com.google.appengine:appengine:1.9.60")
    
    testImplementation("io.ktor:ktor-server-tests:$ktorVersion")
    
    }
    Set up Ktor and AppEngine
    build.gradle.kts
    

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31. build.gradle.kts
    "# Note: the AppEngine plugin currently does something funky when you apply it using the
    
    "# plugins DSL, so we need to use the old-school way for it to be able to work
    
    apply(plugin = "com.google.cloud.tools.appengine")
    
    configure {
    
    deploy {
    
    projectId = "GCLOUD_CONFIG"
    
    version = "GCLOUD_CONFIG"
    
    }
    
    }
    
    repositories {
    
    maven { url = uri("https:"#kotlin.bintray.com/ktor") }
    
    }
    
    dependencies {
    
    val kotlinVersion = rootProject.extra["kotlin_version"]
    
    val ktorVersion = rootProject.extra["ktor_version"]
    
    implementation(kotlin("stdlib-jdk8"))
    
    implementation("ch.qos.logback:logback-classic:1.2.3")
    
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion")
    
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0")
    
    implementation("io.ktor:ktor-server-servlet:$ktorVersion")
    
    implementation("io.ktor:ktor-html-builder:$ktorVersion")
    
    implementation("io.ktor:ktor-auth:$ktorVersion")
    
    implementation("io.ktor:ktor-locations:$ktorVersion")
    
    implementation("io.ktor:ktor-serialization:$ktorVersion")
    
    implementation("io.ktor:ktor-server-host-common:$ktorVersion")
    
    providedCompile("com.google.appengine:appengine:1.9.60")
    
    testImplementation("io.ktor:ktor-server-tests:$ktorVersion")
    
    }
    Set up Ktor and AppEngine
    

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32. Ktor and AppEngine configuration
    • src/main/resources/application.conf
    
    • Ktor main configuration
    

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33. • src/main/resources/application.conf
    
    • Ktor main configuration
    
    • src/main/resources/logback.xml
    
    • Logging configuration
    
    • Two appenders: STDOUT and CLOUD
    Ktor and AppEngine configuration
    

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34. • src/main/webapp/WEB-INF/appengine-web.xml
    
    • AppEngine main configuration
    Ktor and AppEngine configuration
    

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35. • src/main/webapp/WEB-INF/appengine-web.xml
    
    • AppEngine main configuration
    
    • src/main/webapp/WEB-INF/logging.properties
    
    • Cloud logging configuration
    Ktor and AppEngine configuration
    

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36. • src/main/webapp/WEB-INF/appengine-web.xml
    
    • AppEngine main configuration
    
    • src/main/webapp/WEB-INF/logging.properties
    
    • Cloud logging configuration
    
    • src/main/webapp/WEB-INF/web.xml
    
    • Servlet configuration
    Ktor and AppEngine configuration
    

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37. package dev.sebastiano.pushbeat.api
    
    @Suppress(“unused") "# Referenced in application.conf
    
    fun Application.module() {
    
    "# ""&
    
    }
    • In Application.kt
    ktor {
    
    deployment {
    
    port = 8080
    
    port = ${?PORT}
    
    }
    
    application {
    
    modules = [ dev.sebastiano.pushbeat.api.ApplicationKt.module ]
    
    }
    
    }
    • What to start is defined in application.conf
    Start your server up
    

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38. package dev.sebastiano.pushbeat.api
    
    @Suppress(“unused") "# Referenced in application.conf
    
    fun Application.module() {
    
    "# ""&
    
    }
    • In Application.kt
    ktor {
    
    deployment {
    
    port = 8080
    
    port = ${?PORT}
    
    }
    
    application {
    
    modules = [ dev.sebastiano.pushbeat.api.ApplicationKt.module ]
    
    }
    
    }
    • What to start is defined in application.conf
    Start your server up
    

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39. package dev.sebastiano.pushbeat.api
    
    @Suppress(“unused") "# Referenced in application.conf
    
    fun Application.module() {
    
    "# ""&
    
    }
    • In Application.kt
    ktor {
    
    deployment {
    
    port = 8080
    
    port = ${?PORT}
    
    }
    
    application {
    
    modules = [ dev.sebastiano.pushbeat.api.ApplicationKt.module ]
    
    }
    
    }
    • What to start is defined in application.conf
    Start your server up
    

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40. Features
    • Modular design
    
    • Features
    
    • Pluggable pipeline
    
    • Everything is a feature
    
    • Routing, auth, content negotiation, etc.
    
    • Install only the features you need
    

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41. @Suppress("unused") "# Referenced in application.conf
    
    @JvmOverloads
    
    fun Application.module(testing: Boolean = false) {
    
    setupAuthentication()
    
    install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    Features
    install(Authentication) {
    
    basic(AUTHENTICATOR_NAME) {
    
    realm = "PushBeat"
    
    validate {
    
    if (it.name "' "push" "$ it.password "' “beat”) {
    
    UserIdPrincipal(it.name)
    
    } else null
    
    }
    
    }
    
    }
    

    View Slide

42. @Suppress("unused") "# Referenced in application.conf
    
    @JvmOverloads
    
    fun Application.module(testing: Boolean = false) {
    
    setupAuthentication()
    
    install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    Features
    

    View Slide

43. @Suppress("unused") "# Referenced in application.conf
    
    @JvmOverloads
    
    fun Application.module(testing: Boolean = false) {
    
    setupAuthentication()
    
    install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    Features
    

    View Slide

44. @Suppress("unused") "# Referenced in application.conf
    
    @JvmOverloads
    
    fun Application.module(testing: Boolean = false) {
    
    setupAuthentication()
    
    install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    Features
    

    View Slide

45. install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    format { call #$
    
    when (val status = call.response.status() "( "Unhandled") {
    
    HttpStatusCode.Found ") "$status: ${call.request.httpMethod.value} - " +
    
    "${call.request.uri} [accept: '${call.request.accept()}'] ") " +
    
    "${call.response.headers[HttpHeaders.Location]}"
    
    else ") "$status: ${call.request.httpMethod.value} - ${call.request.uri}" +
    
    "[accept: '${call.request.accept()}']"
    
    }
    
    }
    
    }
    
    setupStatusPages(json, logger)
    
    setupRouting(json, BeatSourcesRegistry)
    
    }
    
    Features
    

    View Slide

46. install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    format { call #$
    
    when (val status = call.response.status() "( "Unhandled") {
    
    HttpStatusCode.Found ") "$status: ${call.request.httpMethod.value} - " +
    
    "${call.request.uri} [accept: '${call.request.accept()}'] ") " +
    
    "${call.response.headers[HttpHeaders.Location]}"
    
    else ") "$status: ${call.request.httpMethod.value} - ${call.request.uri}" +
    
    "[accept: '${call.request.accept()}']"
    
    }
    
    }
    
    }
    
    setupStatusPages(json, logger)
    
    setupRouting(json, BeatSourcesRegistry)
    
    }
    
    Features
    

    View Slide

47. install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    format { call #$
    
    when (val status = call.response.status() "( "Unhandled") {
    
    HttpStatusCode.Found ") "$status: ${call.request.httpMethod.value} - " +
    
    "${call.request.uri} [accept: '${call.request.accept()}'] ") " +
    
    "${call.response.headers[HttpHeaders.Location]}"
    
    else ") "$status: ${call.request.httpMethod.value} - ${call.request.uri}" +
    
    "[accept: '${call.request.accept()}']"
    
    }
    
    }
    
    }
    
    setupStatusPages(json, logger)
    
    setupRouting(json, BeatSourcesRegistry)
    
    }
    
    Features
    internal fun Application.setupStatusPages(json: Json, logger: Logger) {
    
    install(StatusPages) {
    
    status(HttpStatusCode.NotFound) { statusCode #$
    
    val message = generate404ErrorMessage(call.request.uri)
    
    call.respondError(json, message, statusCode)
    
    }
    
    exception {
    
    call.respondError(json, "Unauthorized", HttpStatusCode.Unauthorized)
    
    }
    
    exception {
    
    call.respondError(json, "Forbidden", HttpStatusCode.Unauthorized)
    
    }
    
    exception { cause #$
    
    logger.info("Unhandled exception: ${cause.message}", cause)
    
    val errorMessage = "Error while processing the request. ${cause.message}"
    
    call.respondError(json, errorMessage, HttpStatusCode.InternalServerError)
    
    }
    
    }
    
    }
    

    View Slide

48. install(Locations) {
    
    }
    
    @Suppress("MagicNumber") "# Just one-off configuration
    
    install(Compression) {
    
    gzip()
    
    deflate {
    
    priority = 10.0
    
    minimumSize(1024) "# condition
    
    }
    
    }
    
    install(DefaultHeaders) {
    
    header("X-Engine", "Ktor") "# will send this header with each response
    
    }
    
    val json = createJsonInstance()
    
    install(ContentNegotiation) {
    
    json(json)
    
    }
    
    install(CallLogging) {
    
    level = Level.INFO
    
    format { call #$
    
    when (val status = call.response.status() "( "Unhandled") {
    
    HttpStatusCode.Found ") "$status: ${call.request.httpMethod.value} - " +
    
    "${call.request.uri} [accept: '${call.request.accept()}'] ") " +
    
    "${call.response.headers[HttpHeaders.Location]}"
    
    else ") "$status: ${call.request.httpMethod.value} - ${call.request.uri}" +
    
    "[accept: '${call.request.accept()}']"
    
    }
    
    }
    
    }
    
    setupStatusPages(json, logger)
    
    setupRouting(json, BeatSourcesRegistry)
    
    }
    
    Features
    

    View Slide

49. routing {
    
    
    
    get("/") { }
    
    }
    Routing
    

    View Slide

50. routing {
    
    
    
    get("/") { }
    
    post("/") { }
    
    put("/") { }
    
    delete("/") { }
    
    }
    Routing
    

    View Slide

51. routing {
    
    
    
    get("/") { }
    
    post("/") { }
    
    put("/") { }
    
    delete("/") { }
    
    static("static") {
    
    defaultResource("404.html")
    
    }
    
    }
    Routing
    

    View Slide

52. routing {
    
    get("/") { }
    
    post("/") { }
    
    put("/") { }
    
    delete("/") { }
    
    static("static") {
    
    defaultResource("404.html")
    
    }
    
    }
    Routing
    trace { logger.trace(it.buildText()) }
    

    View Slide

53. routing {
    
    get("/") {
    
    }
    
    }
    Responding to a request
    

    View Slide

54. routing {
    
    get("/") {
    
    }
    
    }
    Responding to a request
    :appengineRun
    :appengineDeploy
    call.respondHtml {
    
    head {
    
    title { +"PushBeat" }
    
    }
    
    body {
    
    h1 { +"PushBeat says hi!" }
    
    }
    
    }
    

    View Slide

55. routing {
    
    get("/") {
    
    }
    
    }
    call.respondText(
    
    contentType = ContentType.Application.Json,
    
    text = """{ "status": "OK" }""",
    
    status = HttpStatusCode.OK
    
    )
    Responding to a request
    

    View Slide

56. routing {
    
    }
    Responding to a request
    get("/{id}") {
    
    val id = call.parameters["id"]
    
    val name = call.request.queryParameters["name"]
    
    call.respondText(
    
    contentType ="""{ "id": "$id", "name":
    "$name" }""",
    
    contentType = ContentType.Application.Json
    
    )
    
    

    View Slide

57. internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get("/") {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get("/beats") {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get("/beat/{id}") {
    
    call.handleGetBeat(json, registry)
    
    }
    
    put("/beat/{id}") {
    
    call.handlePutBeat(json, registry)
    
    }
    
    delete("/beat/{id}") {
    
    call.handleDeleteBeat(json, registry)
    
    }
    
    get("/beat/{id}/refresh") {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Routing in PushBeat
    

    View Slide

58. internal fun HTML.renderRegisteredBeats(registry: BeatSourcesRegistry) {
    
    head {
    
    title { +"PushBeat" }
    
    styleLink("/static/css/pushbeat.css")
    
    script(src = "/static/js/pushbeat.js", type = LinkType.textJavaScript) {}
    
    }
    
    body {
    
    h1 { +"PushBeat" }
    
    h2 { +"Registered beats" }
    
    ul {
    
    val sources = registry.sources()
    
    if (sources.isEmpty()) {
    
    li { i { +"None" } }
    
    return@ul
    
    }
    
    for (source in sources) {
    
    li {
    
    p {
    
    b {
    
    +"${source.name} "
    
    span(classes = "secondary") {
    
    +"(id: "
    
    code { +source.id }
    
    +")"
    
    }
    
    }
    
    br
    
    Routing in PushBeat
    

    View Slide

59. internal fun HTML.renderRegisteredBeats(registry: BeatSourcesRegistry) {
    
    head {
    
    title { +"PushBeat" }
    
    styleLink("/static/css/pushbeat.css")
    
    script(src = "/static/js/pushbeat.js", type = LinkType.textJavaScript) {}
    
    }
    
    body {
    
    h1 { +"PushBeat" }
    
    h2 { +"Registered beats" }
    
    ul {
    
    val sources = registry.sources()
    
    if (sources.isEmpty()) {
    
    li { i { +"None" } }
    
    return@ul
    
    }
    
    for (source in sources) {
    
    li {
    
    p {
    
    b {
    
    +"${source.name} "
    
    span(classes = "secondary") {
    
    +"(id: "
    
    code { +source.id }
    
    +")"
    
    }
    
    }
    
    br
    
    +"Last BPM: ${source.beats.valueOrNull "( "N/A"}"
    
    span(classes = "refresh") {
    
    onClick = "javascript:refreshBeatValue('${source.id}'); location.reload();"
    
    +"refresh"
    
    }
    
    }
    
    }
    
    Routing in PushBeat
    

    View Slide

60. internal fun HTML.renderRegisteredBeats(registry: BeatSourcesRegistry) {
    
    head {
    
    title { +"PushBeat" }
    
    styleLink("/static/css/pushbeat.css")
    
    script(src = "/static/js/pushbeat.js", type = LinkType.textJavaScript) {}
    
    }
    
    body {
    
    h1 { +"PushBeat" }
    
    h2 { +"Registered beats" }
    
    ul {
    
    val sources = registry.sources()
    
    if (sources.isEmpty()) {
    
    li { i { +"None" } }
    
    return@ul
    
    }
    
    for (source in sources) {
    
    li {
    
    p {
    
    b {
    
    +"${source.name} "
    
    span(classes = "secondary") {
    
    +"(id: "
    
    code { +source.id }
    
    +")"
    
    }
    
    }
    
    br
    
    +"Last BPM: ${source.beats.valueOrNull "( "N/A"}"
    
    span(classes = "refresh") {
    
    onClick = "javascript:refreshBeatValue('${source.id}'); location.reload();"
    
    +"refresh"
    
    }
    
    }
    
    }
    
    }
    
    }
    
    }
    
    }
    Routing in PushBeat
    

    View Slide

61. title { +"PushBeat" }
    
    styleLink("/static/css/pushbeat.css")
    
    script(src = "/static/js/pushbeat.js", type = LinkType.textJavaScript) {}
    
    }
    
    body {
    
    h1 { +"PushBeat" }
    
    h2 { +"Registered beats" }
    
    ul {
    
    val sources = registry.sources()
    
    if (sources.isEmpty()) {
    
    li { i { +"None" } }
    
    return@ul
    
    }
    
    for (source in sources) {
    
    li {
    
    p {
    
    b {
    
    +"${source.name} "
    
    span(classes = "secondary") {
    
    +"(id: "
    
    code { +source.id }
    
    +")"
    
    }
    
    }
    
    br
    
    +"Last BPM: ${source.beats.valueOrNull "( "N/A"}"
    
    span(classes = "refresh") {
    
    onClick = "javascript:refreshBeatValue('${source.id}'); location.reload();"
    
    +"refresh"
    
    }
    
    }
    
    }
    
    }
    
    }
    
    }
    
    }
    Routing in PushBeat
    

    View Slide

62. internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get("/") {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get("/beats") {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get("/beat/{id}") {
    
    call.handleGetBeat(json, registry)
    
    }
    
    put("/beat/{id}") {
    
    call.handlePutBeat(json, registry)
    
    }
    
    delete("/beat/{id}") {
    
    call.handleDeleteBeat(json, registry)
    
    }
    
    get("/beat/{id}/refresh") {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    defaultResource("404.html")
    
    }
    
    }
    
    }
    
    private fun Route.resourceFolder(name: String) {
    
    static(name) { resources(name) }
    
    }
    Routing in PushBeat
    

    View Slide

63. internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get("/") {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get("/beats") {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get("/beat/{id}") {
    
    call.handleGetBeat(json, registry)
    
    }
    
    put("/beat/{id}") {
    
    call.handlePutBeat(json, registry)
    
    }
    
    delete("/beat/{id}") {
    
    call.handleDeleteBeat(json, registry)
    
    }
    
    get("/beat/{id}/refresh") {
    
    call.handleGetRefreshBeat(json, registry)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Improving routing: locations
    

    View Slide

64. internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Improving routing: locations
    

    View Slide

65. internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Improving routing: locations
    

    View Slide

66. @Location("/")
    
    class RootLocation
    
    @Location("/beats")
    
    class BeatsLocation
    
    @Location("/beat/{id}")
    
    class BeatLocation(val id: String) {
    
    @Location("/refresh")
    
    class Refresh(val beatLocation: BeatLocation)
    
    }
    SourcesRegistry) {
    
    
    
    ation.id)
    
    Improving routing: locations
    

    View Slide

67. @Location("/beat/{id}")
    
    class BeatLocation(val id: String) {
    
    @Location("/refresh")
    
    class Refresh(
    
    val beatLocation: BeatLocation
    
    )
    
    }
    internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Improving routing: locations
    

    View Slide

68. @Location("/beat/{id}")
    
    class BeatLocation(val id: String) {
    
    @Location("/refresh")
    
    class Refresh(
    
    val beatLocation: BeatLocation
    
    )
    
    }
    internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Improving routing: locations
    

    View Slide

69. @Location("/beat/{id}")
    
    class BeatLocation(val id: String) {
    
    @Location("/refresh")
    
    class Refresh(
    
    val beatLocation: BeatLocation
    
    )
    
    }
    internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    
    static("static") {
    
    resourceFolder("css")
    
    resourceFolder("js")
    
    Improving routing: locations
    

    View Slide

70. internal fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    routing {
    
    authenticate(AUTHENTICATOR_NAME) {
    
    }
    
    static("static") {
    
    Basic authentication
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    

    View Slide

71. al fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    uting {
    
    authenticate(AUTHENTICATOR_NAME) {
    
    }
    
    static("static") {
    
    Basic authentication
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    ""* Get registered beat providers (HTML)
    
    GET http:"#localhost:8080/
    
    Accept: 'text/html'
    

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72. al fun Application.setupRouting(json: Json, registry: BeatSourcesRegistry) {
    
    uting {
    
    authenticate(AUTHENTICATOR_NAME) {
    
    }
    
    static("static") {
    
    Basic authentication
    get {
    
    call.respondHtml { renderRegisteredBeats(registry) }
    
    }
    
    get {
    
    call.handleGetBeatSources(json, registry)
    
    }
    
    get {
    
    call.handleGetBeat(json, registry, it.id)
    
    }
    
    put {
    
    call.handlePutBeat(json, registry, it.id)
    
    }
    
    delete {
    
    call.handleDeleteBeat(json, registry, it.id)
    
    }
    
    get {
    
    call.handleGetRefreshBeat(json, registry, it.beatLocation.id)
    
    }
    ""* Get registered beat providers (HTML)
    
    GET http:"#localhost:8080/
    
    Accept: 'text/html'
    
    Authorization: Basic push beat
    

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73. Image credits Some images designed by Freepik / rawpixel.com, macrovector; octicons
    Question
    time!
    

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74. Thanks!
    

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