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KTOR FOR MOBILE
DEVELOPERS
DAN KIM
@dankim
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Server side code? Me?
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No content
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It's been...a while
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The paradox of choice
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"I wish there was a way to do simple
server stuff with what I already
know..."
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Something familiar
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Something that maintains
my focus
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Something lightweight
and simple
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Enter Ktor!
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So here's what we're
gonna do...
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A Google "Dashboard"
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RESTful API
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Bonus: WebApp!
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Let's build the RESTful
API!
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Things we'll be using
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Ktor
OAuth2
Retrofit
Moshi
Google APIs
Google Cloud
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Things we're not going to
get into
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Quickstart
Database
Sessions
Testing
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Assumptions
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You've setup an application
on Google Cloud
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You've authenticated to
Google's OAuth2
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Ktor's basic structure
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ApplicationEngine
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CIO
Jetty
Netty
Tomcat
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Netty
CIO
Jetty
Tomcat
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fun main(args: Array) {
io.ktor.server.netty.EngineMain.main(args)
}
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ApplicationEnvironment
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application.conf
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ktor {
deployment {
port = 8080
watch = [Dev/kotlin/ktor/src]
}1
application {
modules = [com.dankim.ApplicationKt.module]
}1
}1
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ktor {
deployment {
port = 8080
watch = [Dev/kotlin/ktor/src]
}1
application {
modules = [com.dankim.ApplicationKt.module]
}1
}1
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fun main(args: Array) {
io.ktor.server.netty.EngineMain.main(args)
}
fun Application.module() {
}
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Application
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class Application(val environment: ApplicationEnvironment) :
ApplicationCallPipeline(), CoroutineScope {
...
}1
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class Application(val environment: ApplicationEnvironment) :
ApplicationCallPipeline(), CoroutineScope {
...
}1
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ApplicationCallPipeline
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ApplicationCallPipeline
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Phase 1
Phase 2
Phase 3
Phase 5
Phase 4
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Interceptor
Interceptor Interceptor
Interceptor
Interceptor
Interceptor Interceptor
Interceptor
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1. Setup
2. Monitoring
3. Features
4. Call
5. Fallback
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Features
Call
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Features
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No content
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DefaultHeaders Feature
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fun Application.module() {
}1
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curl -v http://0.0.0.0:8080/
>
< HTTP/1.1 404 Not Found
< Content-Length: 0
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fun Application.module() {
}1
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fun Application.module() {
install(DefaultHeaders)
}1
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override fun install(...): DefaultHeaders {
...
val feature = DefaultHeaders(config)
pipeline.intercept(ApplicationCallPipeline.Features) {
feature.intercept(call)
}
...
}
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curl -v http://0.0.0.0:8080/
< HTTP/1.1 404 Not Found
< Date: Wed, 13 Nov 2019 02:08:13 GMT
< Server: ktor-server-core/1.2.4 ktor-server-core/
1.2.4
< Content-Length: 0
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Routes
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fun Application.module() {
install(DefaultHeaders)
}1
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fun Application.module() {
install(DefaultHeaders)
install(Routing)
}1
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override fun install(...): Routing {
...
val routing = Routing(pipeline).apply(configure)
pipeline.intercept(ApplicationCallPipeline.Call) {
routing.interceptor(this)
}
...
}
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Features
Call
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fun Application.module() {
install(DefaultHeaders)
install(Routing)
}
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curl -v http://0.0.0.0:8080/
< HTTP/1.1 404 Not Found
< Date: Wed, 13 Nov 2019 02:08:13 GMT
< Server: ktor-server-core/1.2.4 ktor-server-core/
1.2.4
< Content-Length: 0
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fun Application.module() {
install(DefaultHeaders)
install(Routing)
}11
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fun Application.module() {
install(DefaultHeaders)
install(Routing) {
get("/dashboard.json") {
call.respondText {
"Hello KotlinConf!"
}11
}11
}11
}11
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curl -v http://0.0.0.0:8080/
< HTTP/1.1 200 OK
< Date: Tue, 03 Dec 2019 15:33:23 GMT
< Server: ktor-server-core/1.2.4 ktor-server-core/
1.2.4
...
Hello KotlinConf!
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Let's get some data
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GET Gmail Data
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@JsonClass(generateAdapter = true)11
data class GmailThreads(
@Json(name = "threads") val threads: List
)111
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@JsonClass(generateAdapter = true)11
data class GmailThreads(
@Json(name = "threads") val threads: List
)111
@JsonClass(generateAdapter = true)
data class GmailThread(
@Json(name = "id") val id: String,
@Json(name = "snippet") val snippet: String
)1
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@GET("gmail/v1/users/{user}/threads")
fun getGmailThreads(@Path("user") user: String): Call
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private fun getGmailData(): GmailThreads? {
val response =
getGoogleServicesInstance()
.getGmailThreads("[email protected]")
.execute()
return when {
response.isSuccessful -> response.body()
else -> {
handleError(response.errorBody().toString())
null
}1
}1
}1
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private fun getGmailData(): GmailThreads? {
val response =
getGoogleServicesInstance()
.getGmailThreads("[email protected]")
.execute()
return when {
response.isSuccessful -> response.body()
else -> {
handleError(response.errorBody().toString())
null
}1
}1
}1
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private fun getGmailData(): GmailThreads? {
val response =
getGoogleServicesInstance()
.getGmailThreads("[email protected]")
.execute()
return when {
response.isSuccessful -> response.body()
else -> {
handleError(response.errorBody().toString())
null
}1
}1
}1
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fun Application.module() {
install(DefaultHeaders)
install(Routing) {
}11
}1
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fun Application.module() {
install(DefaultHeaders)
install(Routing) {
get("/dashboard.json") {
val gmailData = getGmailData()
call.respondText {
gmailData.toJson()
}1111
}111
}11
}1
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fun Application.module() {
install(DefaultHeaders)
install(Routing) {
get("/dashboard.json") {
val gmailData = getGmailData()
call.respondText {
gmailData.toJson()
}1
}1
}1
}1
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fun Application.module() {
install(DefaultHeaders)
install(Routing) {
get("/dashboard.json") {
val gmailData = getGmailData()
call.respondText {
gmailData.toJson()
}1
}1
}1
}1
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curl -H "Authorization: Bearer "
http://0.0.0.0:8080/dashboard.json
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curl -H "Authorization: Bearer " http://0.0.0.0:8080/dashboard.json
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GET Gtasks Data
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@JsonClass(generateAdapter = true)111
data class GoogleTasks(
@Json(name = "items") val tasks: List? = null
)111
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@JsonClass(generateAdapter = true)111
data class GoogleTasks(
@Json(name = "items") val tasks: List? = null
)111
@JsonClass(generateAdapter = true)11
data class GoogleTask(
@Json(name = "id") val id: String? = null,
@Json(name = "title") val title: String? = null,
@Json(name = "status") val status: String? = null
)11
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@JsonClass(generateAdapter = true)111
data class GoogleTasks(
@Json(name = "items") val tasks: List? = null
)111
@JsonClass(generateAdapter = true)11
data class GoogleTask(
@Json(name = "id") val id: String? = null,
@Json(name = "title") val title: String? = null,
@Json(name = "status") val status: String? = null
)11
@JsonClass(generateAdapter = true)1
data class MyGoogleDashboard(
@Json(name = "tasks") val tasks: List,
@Json(name = "emails") val emails: List
)1
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@GET("tasks/v1/lists/{listId}/tasks")
fun getTasks(@Path("listId") listId: String): Call
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private fun getTaskList(listId: String): GoogleTasks? {
val response =
getGoogleServicesInstance().getTasks(listId).execute()
return if (response.isSuccessful) {
response.body()
} else {
handleError(response.errorBody().toString())
null
}1
}1
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private fun getTaskList(listId: String): GoogleTasks? {
val response =
getGoogleServicesInstance().getTasks(listId).execute()
return if (response.isSuccessful) {
response.body()
} else {
handleError(response.errorBody().toString())
null
}1
}1
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private fun getTaskList(listId: String): GoogleTasks? {
val response =
getGoogleServicesInstance().getTasks(listId).execute()
return if (response.isSuccessful) {
response.body()
} else {
handleError(response.errorBody().toString())
null
}1
}1
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get("/dashboard.json") {
val gmailData = getGmailData()
val taskList = getTaskList("")
val myGoogleDashboard = MyGoogleDashboard(
tasks = taskList?.tasks,
emails = gmailData?.threads
)
call.respondText {
myGoogleDashboard.toJson()
}1
}1
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get("/dashboard.json") {
val gmailData = getGmailData()
val taskList = getTaskList("")
val myGoogleDashboard = MyGoogleDashboard(
tasks = taskList?.tasks,
emails = gmailData?.threads
)
call.respondText {
myGoogleDashboard.toJson()
}1
}1
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get("/dashboard.json") {
val gmailData = getGmailData()
val taskList = getTaskList("")
val myGoogleDashboard = MyGoogleDashboard(
tasks = taskList?.tasks,
emails = gmailData?.threads
)
call.respondText {
myGoogleDashboard.toJson()
}1
}1
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get("/dashboard.json") {
val gmailData = getGmailData()
val taskList = getTaskList("")
val myGoogleDashboard = MyGoogleDashboard(
tasks = taskList?.tasks,
emails = gmailData?.threads
)
call.respondText {
myGoogleDashboard.toJson()
}1
}1
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curl -H "Authorization: Bearer "
http://0.0.0.0:8080/dashboard.json
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curl -H "Authorization: Bearer " http://0.0.0.0:8080/dashboard.json
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Gtasks POST
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@POST("tasks/v1/lists/{listId}/tasks")
fun createTask(@Path("listId") listId: String, @Body task: GoogleTask):
Call
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val task = GoogleTask(title = taskName)
val response =
getGoogleServicesInstance().createTask("",task).execute()
return if (response.isSuccessful) {
call.respond(HttpStatusCode.OK)
} else {
handleError(response.errorBody().toString())
null
}1
}1
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val task = GoogleTask(title = taskName)
val response =
getGoogleServicesInstance().createTask("",task).execute()
return if (response.isSuccessful) {
call.respond(HttpStatusCode.OK)
} else {
handleError(response.errorBody().toString())
null
}1
}1
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val task = GoogleTask(title = taskName)
val response =
getGoogleServicesInstance().createTask("",task).execute()
return if (response.isSuccessful) {
call.respond(HttpStatusCode.OK)
} else {
handleError(response.errorBody().toString())
null
}1
}1
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val task = GoogleTask(title = taskName)
val response =
getGoogleServicesInstance().createTask("",task).execute()
return if (response.isSuccessful) {
call.respond(HttpStatusCode.OK)
} else {
handleError(response.errorBody().toString())
null
}1
}1
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val task = GoogleTask(title = taskName)
val response =
getGoogleServicesInstance().createTask("",task).execute()
return if (response.isSuccessful) {
call.respond(HttpStatusCode.OK)
} else {
handleError(response.errorBody().toString())
null
}1
}1
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curl -v -F 'taskName=This is super cool!' -H "Accept: application/json"
http://0.0.0.0:8080/tasks/new
< HTTP/1.1 200 OK
< Date: Tue, 19 Nov 2019 02:58:41 GMT
< Server: ktor-server-core/1.2.4 ktor-server-core/1.2.4
< Content-Length: 0
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No content
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Webapp
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Authentication
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OAuth 2
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No content
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val googleOauthProvider =
OAuthServerSettings.OAuth2ServerSettings(
name = "google",
authorizeUrl = "https://accounts.google.com/o/oauth2/auth",
accessTokenUrl = "https://www.googleapis.com/oauth2/v3/token",
requestMethod = HttpMethod.Post,
clientId = "",
clientSecret = "",
defaultScopes = listOf(
"profile",
"email",
"https://www.googleapis.com/auth/gmail.readonly",
"https://www.googleapis.com/auth/tasks"
)
)
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fun Application.module() {
// ...
install(Authentication) {
oauth("google-oauth") {
client = HttpClient(Apache)
providerLookup = { googleOauthProvider }
urlProvider = { redirectUrl("/login") }
}
}
}
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fun Application.module() {
...
install(Routing) {
authenticate("google-oauth") {
route("/login") {
handle {
val principal =
call.authentication.principal()
?: error("No principal")
saveOAuthToken(principal.accessToken)
call.respondRedirect("/")
}11111
}1111
}1111
}11
}11
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fun Application.module() {
...
install(Routing) {
authenticate("google-oauth") {
route("/login") {
handle {
val principal =
call.authentication.principal()
?: error("No principal")
saveOAuthToken(principal.accessToken)
call.respondRedirect("/")
}11111
}1111
}111
}11
}11
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fun Application.module() {
...
install(Routing) {
authenticate("google-oauth") {
route("/login") {
handle {
val principal =
call.authentication.principal()
?: error("No principal")
saveOAuthToken(principal.accessToken)
call.respondRedirect("/")
}1
}1
}1
}1
}1
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Web: showing the data
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get("/dashboard") {
val gmailData = getGmailData()
val taskList = getTaskList("")
...
}
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call.respondHtml {
body {
p {
h1 { +"Dashboard" }
h2 { +"Tasks:" }
ul {
taskList?.tasks?.forEach {
li { +it.title!! }
}1
}1
h2 { +"Emails:" }
ul {
gmailData?.threads?.forEach {
li { +StringEscapeUtils.unescapeHtml4(it.snippet) }
}1
}1
}1
}1
}1
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body {
p {
h1 { +"Dashboard" }
h2 { +"Tasks:" }
ul {
taskList?.tasks?.forEach {
li { +it.title }
}11
}11
h2 { +"Emails:" }
ul {
gmailData?.threads?.forEach {
li { +StringEscapeUtils.unescapeHtml4(it.snippet) }
}1
}1
}1
}1
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body {
p {
h1 { +"Dashboard" }
h2 { +"Tasks:" }
ul {11
taskList?.tasks?.forEach {
li { +it.title }
}11
}11
h2 { +"Emails:" }
ul {1
gmailData?.threads?.forEach {
li { +StringEscapeUtils.unescapeHtml4(it.snippet) }
}1
}1
}1
}1
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body {
p {
h1 { +"Dashboard" }
h2 { +"Tasks:" }
ul {11
taskList?.tasks?.forEach {
li { +it.title }
}11
}11
h2 { +"Emails:" }
ul {1
gmailData?.threads?.forEach {
li { +StringEscapeUtils.unescapeHtml4(it.snippet) }
}1
}1
}1
}1
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No content
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Web: posting data
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get("/tasks/new") {
call.respondHtml {
body {
form("/tasks/new",
encType = FormEncType.applicationXWwwFormUrlEncoded,
method = FormMethod.post
) {
acceptCharset = "utf-8"
p {
label { +"Task: " }
textInput { name = "taskName" }
}1
p {
submitInput { value = "send" }
}1
}1
}1
}1
}1
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get("/tasks/new") {
call.respondHtml {
body {
form("/tasks/new",
encType = FormEncType.applicationXWwwFormUrlEncoded,
method = FormMethod.post
) {
acceptCharset = "utf-8"
p {
label { +"Task: " }
textInput { name = "taskName" }
}111111
p {
submitInput { value = "send" }
}11111
}1111
}111
}111
}1
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get("/tasks/new") {
call.respondHtml {
body {
form("/tasks/new",
encType = FormEncType.applicationXWwwFormUrlEncoded,
method = FormMethod.post
) {
acceptCharset = "utf-8"
p {
label { +"Task: " }
textInput { name = "taskName" }
}111111
p {
submitInput { value = "send" }
}11111
}1111
}111
}11
}1
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No content
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val acceptHeader = call.request.headers.get("Accept")
val task = GoogleTask(title = taskName)
val response = getGoogleServicesInstance().createTask(
"", task).execute()
when (acceptHeader) {
"application/json" -> call.respond(HttpStatusCode.OK)
else -> call.respondRedirect("/dashboard")
}1
}1
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val acceptHeader = call.request.headers.get("Accept")
val task = GoogleTask(title = taskName)
val response = getGoogleServicesInstance().createTask(
"", task).execute()
when (acceptHeader) {
"application/json" -> call.respond(HttpStatusCode.OK)
else -> call.respondRedirect("/dashboard")
}1
}1
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post("/tasks/new") {
val postParams = call.receiveParameters()
val taskName = postParams.entries()
.find { it.key == "taskName" }?.value?.first()
val acceptHeader = call.request.headers.get("Accept")
val task = GoogleTask(title = taskName)
val response = getGoogleServicesInstance().createTask(
"", task).execute()
when (acceptHeader) {
"application/json" -> call.respond(HttpStatusCode.OK)
else -> call.respondRedirect("/dashboard")
}1
}1
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No content
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Deployment
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Google Cloud
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https://cloud.google.com/
community/tutorials/kotlin-ktor-app-
engine-java8
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XML config files
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../src/main/webapp/WEB-INF/appengine-web.xml
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../src/main/webapp/WEB-INF/appengine-web.xml
../src/main/webapp/WEB-INF/web.xml
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Cloud projects cost
money!
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No content
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gcloud projects delete [PROJECT_ID]
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Wrap it up!
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THANK YOU
AND
REMEMBER
TO VOTE
Dan Kim @dankim