feat(samples): serve frontend from Kotlin backend via Gradle build

- Add node-gradle plugin to build frontend as part of ./gradlew run
- Vite outputs to backend's src/main/resources/static/
- Ktor serves static files at / (after API routes)
- Update README with single-command and dev-server run options

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pengying

samples/frontend/vite.config.ts

@@ -4,6 +4,10 @@ import tailwindcss from '@tailwindcss/vite'
 
 export default defineConfig({
   plugins: [react(), tailwindcss()],
+  build: {
+    outDir: '../kotlin/src/main/resources/static',
+    emptyOutDir: true,
+  },
   server: {
     port: 5173,
     proxy: {

samples/kotlin/.gitignore

@@ -0,0 +1,9 @@
+# Gradle
+.gradle/
+build/
+
+# Frontend build output (generated by vite build)
+src/main/resources/static/
+
+# Environment
+.env

samples/kotlin/README.md

@@ -38,7 +38,20 @@ Webhook events are streamed to the frontend in real time via Server-Sent Events
 
 ## Running
 
-Start the backend and frontend in two separate terminals:
+### Option 1: Single command (recommended)
+
+The Gradle build automatically installs frontend dependencies, builds the React app, and serves it from the backend:
+
+```bash
+cd samples/kotlin
+./gradlew run
+```
+
+Open [http://localhost:8080](http://localhost:8080) in your browser.
+
+### Option 2: Separate dev servers (for frontend development)
+
+If you're iterating on the frontend, run them separately for hot reload:
 
 **Terminal 1 — Backend (port 8080):**
 
@@ -55,7 +68,7 @@ npm install
 npm run dev
 ```
 
-Open [http://localhost:5173](http://localhost:5173) in your browser.
+Open [http://localhost:5173](http://localhost:5173) in your browser. The Vite dev server proxies `/api` requests to the backend.
 
 ## Webhook Setup
 

samples/kotlin/build.gradle.kts

@@ -2,6 +2,22 @@ plugins {
     kotlin("jvm") version "2.1.21"
     kotlin("plugin.serialization") version "2.1.21"
     id("io.ktor.plugin") version "3.1.3"
+    id("com.github.node-gradle.node") version "7.1.0"
+}
+
+node {
+    version.set("22.15.0")
+    download.set(true)
+    nodeProjectDir.set(file("../frontend"))
+}
+
+val npmBuild by tasks.register<com.github.gradle.node.npm.task.NpmTask>("npmBuild") {
+    dependsOn(tasks.named("npmInstall"))
+    args.set(listOf("run", "build"))
+}
+
+tasks.named("processResources") {
+    dependsOn("npmBuild")
 }
 
 kotlin {

samples/kotlin/src/main/kotlin/com/grid/sample/Application.kt

@@ -4,6 +4,7 @@ import com.grid.sample.routes.*
 import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.plugins.cors.routing.*
+import io.ktor.server.http.content.*
 import io.ktor.server.routing.*
 import io.ktor.server.sse.*
 
@@ -29,5 +30,8 @@ fun Application.module() {
         sandboxRoutes()
         webhookRoutes()
         sseRoutes()
+
+        // Serve frontend static files — must come last to avoid catching API routes
+        staticResources("/", "static")
     }
 }