Fixed: #3963 Added Kotlin Spring Boot Example (#3965)

# Pull Request 
Added Kotlin Example for Spring Boot 
Fixes: #3963

## Description
Adds Example for Kotlin Spring Boot `6-hello-spring-boot` and
`7-todo-spring-boot`

## Related Issues
- Link to related issue #3963.

## Checklist
- [x] New Example For Kotlin Spring Boot Hello World
- [x] New Example for Kotlin Spring Boot Todo MVC

## Status
Completed Addition

docs/modules/ROOT/pages/kotlinlib/web-examples.adoc

@@ -24,3 +24,11 @@ include::partial$example/kotlinlib/web/4-webapp-kotlinjs.adoc[]
 == Ktor KotlinJS Code Sharing
 
 include::partial$example/kotlinlib/web/5-webapp-kotlinjs-shared.adoc[]
+
+== Spring Boot Hello World App
+
+include::partial$example/kotlinlib/web/6-hello-spring-boot.adoc[]
+
+== Spring Boot TodoMvc App
+
+include::partial$example/kotlinlib/web/7-todo-spring-boot.adoc[]

example/kotlinlib/web/6-hello-spring-boot/build.mill

@@ -0,0 +1,37 @@
+package build
+import mill._, kotlinlib._
+
+object `package` extends RootModule with KotlinModule {
+
+  def kotlinVersion = "1.9.24"
+
+  def mainClass = Some("com.example.HelloSpringBootKt")
+
+  def ivyDeps = Agg(
+    ivy"org.springframework.boot:spring-boot-starter-web:2.5.6",
+    ivy"org.springframework.boot:spring-boot-starter-actuator:2.5.6"
+  )
+
+  object test extends KotlinTests with TestModule.Junit5 {
+    def ivyDeps = super.ivyDeps() ++ Agg(
+      ivy"org.springframework.boot:spring-boot-starter-test:2.5.6"
+    )
+  }
+}
+
+// This example demonstrates how to set up a simple Spring Boot webserver,
+// able to handle a single HTTP request at `/` and reply with a single response.
+
+/** Usage
+
+> mill test
+...com.example.HelloSpringBootTest#shouldReturnDefaultMessage() finished...
+
+> mill runBackground
+
+> curl http://localhost:8095
+...<h1>Hello, World!</h1>...
+
+> mill clean runBackground
+
+*/

example/kotlinlib/web/6-hello-spring-boot/resources/application.properties

@@ -0,0 +1 @@
+server.port=8095

example/kotlinlib/web/6-hello-spring-boot/src/com/example/HelloSpringBoot.kt

@@ -0,0 +1,19 @@
+package com.example
+
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.runApplication
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RestController
+
+@SpringBootApplication
+open class HelloSpringBoot
+
+fun main(args: Array<String>) {
+    runApplication<HelloSpringBoot>(*args)
+}
+
+@RestController
+class HelloController {
+    @GetMapping("/")
+    fun hello(): String = "<h1>Hello, World!</h1>"
+}

example/kotlinlib/web/6-hello-spring-boot/test/src/com/example/HelloSpringBootTest.kt

@@ -0,0 +1,24 @@
+package com.example
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.test.context.SpringBootTest
+import org.springframework.boot.test.web.client.TestRestTemplate
+import org.springframework.boot.web.server.LocalServerPort
+
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+class HelloSpringBootTest {
+
+    @LocalServerPort
+    private var port: Int = 0
+
+    @Autowired
+    private lateinit var restTemplate: TestRestTemplate
+
+    @Test
+    fun shouldReturnDefaultMessage() {
+        val response = restTemplate.getForObject("http://localhost:$port/", String::class.java)
+        assertEquals("<h1>Hello, World!</h1>", response)
+    }
+}

example/kotlinlib/web/7-todo-spring-boot/build.mill

@@ -0,0 +1,70 @@
+package build
+import mill._, kotlinlib._
+
+object `package` extends RootModule with KotlinModule {
+  def kotlinVersion = "1.9.24"
+
+  def mainClass = Some("com.example.TodomvcApplicationKt")
+  def ivyDeps = Agg(
+    ivy"org.springframework.boot:spring-boot-starter-data-jpa:2.5.4",
+    ivy"org.springframework.boot:spring-boot-starter-thymeleaf:2.5.4",
+    ivy"org.springframework.boot:spring-boot-starter-validation:2.5.4",
+    ivy"org.springframework.boot:spring-boot-starter-web:2.5.4",
+    ivy"org.jetbrains.kotlin:kotlin-reflect:2.0.21",
+    ivy"javax.xml.bind:jaxb-api:2.3.1",
+    ivy"org.webjars:webjars-locator:0.41",
+    ivy"org.webjars.npm:todomvc-common:1.0.5",
+    ivy"org.webjars.npm:todomvc-app-css:2.4.1"
+  )
+
+  trait HelloTests extends KotlinTests with TestModule.Junit5 {
+    def mainClass = Some("com.example.TodomvcApplicationKt")
+    def ivyDeps = super.ivyDeps() ++ Agg(
+      ivy"org.springframework.boot:spring-boot-starter-test:2.5.6"
+    )
+  }
+
+  object test extends HelloTests {
+    def ivyDeps = super.ivyDeps() ++ Agg(
+      ivy"com.h2database:h2:2.3.230"
+    )
+  }
+
+  object integration extends HelloTests {
+    def ivyDeps = super.ivyDeps() ++ Agg(
+      ivy"org.testcontainers:testcontainers:1.18.0",
+      ivy"org.testcontainers:junit-jupiter:1.18.0",
+      ivy"org.testcontainers:postgresql:1.18.0",
+      ivy"org.postgresql:postgresql:42.6.0"
+    )
+  }
+}
+
+// This is a larger example using Spring Boot, implementing the well known
+// https://todomvc.com/[TodoMVC] example app. Apart from running a webserver,
+// this example also demonstrates:
+//
+// * Serving HTML templates using Thymeleaf
+// * Serving static Javascript and CSS using Webjars
+// * Querying a SQL database using JPA and H2
+// * Unit testing using a H2 in-memory database
+// * Integration testing using Testcontainers Postgres in Docker
+
+/** Usage
+
+> mill test
+...com.example.TodomvcTests#homePageLoads() finished...
+...com.example.TodomvcTests#addNewTodoItem() finished...
+
+> mill integration
+...com.example.TodomvcIntegrationTests#homePageLoads() finished...
+...com.example.TodomvcIntegrationTests#addNewTodoItem() finished...
+
+> mill test.runBackground
+
+> curl http://localhost:8099
+...<h1>todos</h1>...
+
+> mill clean runBackground
+
+*/

example/kotlinlib/web/7-todo-spring-boot/integration/resources/application.properties

@@ -0,0 +1,3 @@
+spring.mvc.hiddenmethod.filter.enabled=true
+spring.jpa.hibernate.ddl-auto=update
+spring.datasource.driver-class-name=org.postgresql.Driver

example/kotlinlib/web/7-todo-spring-boot/integration/src/com/example/TodomvcIntegrationTests.kt

@@ -0,0 +1,76 @@
+package com.example
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.test.context.SpringBootTest
+import org.springframework.boot.test.web.client.TestRestTemplate
+import org.springframework.boot.web.server.LocalServerPort
+import org.springframework.http.HttpEntity
+import org.springframework.http.HttpHeaders
+import org.springframework.http.HttpMethod
+import org.springframework.http.MediaType
+import org.springframework.test.context.DynamicPropertyRegistry
+import org.springframework.test.context.DynamicPropertySource
+import org.testcontainers.containers.PostgreSQLContainer
+import org.testcontainers.junit.jupiter.Container
+import org.testcontainers.junit.jupiter.Testcontainers
+
+@Testcontainers
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+class TodomvcIntegrationTests {
+
+    companion object {
+        @Container
+        val postgresContainer = PostgreSQLContainer<Nothing>("postgres:latest").apply {
+            withDatabaseName("test")
+            withUsername("test")
+            withPassword("test")
+        }
+
+        @JvmStatic
+        @DynamicPropertySource
+        fun postgresProperties(registry: DynamicPropertyRegistry) {
+            registry.add("spring.datasource.url", postgresContainer::getJdbcUrl)
+            registry.add("spring.datasource.username", postgresContainer::getUsername)
+            registry.add("spring.datasource.password", postgresContainer::getPassword)
+        }
+    }
+
+    @LocalServerPort
+    private var port: Int = 0
+
+    @Autowired
+    private lateinit var restTemplate: TestRestTemplate
+
+    @Test
+    fun homePageLoads() {
+        val response = restTemplate.getForEntity("http://localhost:$port/", String::class.java)
+        assertThat(response.statusCode.is2xxSuccessful).isTrue
+        assertThat(response.body).contains("<h1>todos</h1>")
+    }
+
+    @Test
+    fun addNewTodoItem() {
+        // Set up headers and form data for the POST request
+        val headers = HttpHeaders().apply {
+            contentType = MediaType.APPLICATION_FORM_URLENCODED
+        }
+        val newTodo = "title=Test+Todo"
+        val entity = HttpEntity(newTodo, headers)
+
+        // Send the POST request to add a new todo item
+        val postResponse = restTemplate.exchange(
+            "http://localhost:$port/",
+            HttpMethod.POST,
+            entity,
+            String::class.java,
+        )
+        assertThat(postResponse.statusCode.is3xxRedirection).isTrue
+
+        // Send a GET request to verify the new todo item was added
+        val getResponse = restTemplate.getForEntity("http://localhost:$port/", String::class.java)
+        assertThat(getResponse.statusCode.is2xxSuccessful).isTrue
+        assertThat(getResponse.body).contains("Test Todo")
+    }
+}

example/kotlinlib/web/7-todo-spring-boot/resources/templates/fragments.html

@@ -0,0 +1,16 @@
+<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org" lang="en">
+<li th:fragment="todoItem(item)" th:classappend="${item.completed?'completed':''}">
+    <div class="view">
+        <form th:action="@{/{id}/toggle(id=${item.id})}" th:method="put">
+            <input class="toggle" type="checkbox"
+                   onchange="this.form.submit()"
+                   th:attrappend="checked=${item.completed?'true':null}">
+            <label th:text="${item.title}">Taste JavaScript</label>
+        </form>
+        <form th:action="@{/{id}(id=${item.id})}" th:method="delete">
+            <button class="destroy"></button>
+        </form>
+    </div>
+    <input class="edit" value="Create a TodoMVC template">
+</li>
+</html>

example/kotlinlib/web/7-todo-spring-boot/resources/templates/index.html

@@ -0,0 +1,84 @@
+<!doctype html>
+<html xmlns="http://www.w3.org/1999/xhtml"
+      xmlns:th="http://www.thymeleaf.org"
+      lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>Template • TodoMVC</title>
+    <link rel="stylesheet" th:href="@{/webjars/todomvc-common/base.css}">
+    <link rel="stylesheet" th:href="@{/webjars/todomvc-app-css/index.css}">
+</head>
+<body>
+<section class="todoapp">
+    <header class="header">
+        <h1>todos</h1>
+        <form th:action="@{/}" method="post" th:object="${item}">
+            <input class="new-todo" placeholder="What needs to be done?" autofocus
+                   th:field="*{title}">
+        </form>
+    </header>
+    <!-- This section should be hidden by default and shown when there are todos -->
+    <section class="main" th:if="${totalItemCount > 0}">
+        <form th:action="@{/toggle-all}" th:method="put">
+            <input id="toggle-all" class="toggle-all" type="checkbox"
+                   onclick="this.form.submit()">
+            <label for="toggle-all">Mark all as complete</label>
+        </form>
+        <ul class="todo-list" th:remove="all-but-first">
+            <li th:insert="fragments :: todoItem(${item})" th:each="item : ${todoItems}" th:remove="tag">
+            </li>
+            <!-- These are here just to show the structure of the list items -->
+            <!-- List items should get the class `editing` when editing and `completed` when marked as completed -->
+            <li class="completed">
+                <div class="view">
+                    <input class="toggle" type="checkbox" checked>
+                    <label>Taste JavaScript</label>
+                    <button class="destroy"></button>
+                </div>
+                <input class="edit" value="Create a TodoMVC template">
+            </li>
+            <li>
+                <div class="view">
+                    <input class="toggle" type="checkbox">
+                    <label>Buy a unicorn</label>
+                    <button class="destroy"></button>
+                </div>
+                <input class="edit" value="Rule the web">
+            </li>
+        </ul>
+    </section>
+    <!-- This footer should be hidden by default and shown when there are todos -->
+    <footer class="footer" th:if="${totalItemCount > 0}">
+        <th:block th:unless="${activeItemCount == 1}">
+            <span class="todo-count"><strong th:text="${activeItemCount}">0</strong> items left</span>
+        </th:block>
+        <th:block th:if="${activeItemCount == 1}">
+            <span class="todo-count"><strong>1</strong> item left</span>
+        </th:block>
+        <ul class="filters">
+            <li>
+                <a th:href="@{/}"
+                   th:classappend="${todoFilter.name() == 'ALL'?'selected':''}">All</a>
+            </li>
+            <li>
+                <a th:href="@{/active}"
+                   th:classappend="${todoFilter.name() == 'ACTIVE'?'selected':''}">Active</a>
+            </li>
+            <li>
+                <a th:href="@{/completed}"
+                   th:classappend="${todoFilter.name() == 'COMPLETED'?'selected':''}">Completed</a>
+            </li>
+        </ul>
+        <form th:action="@{/completed}" th:method="delete"
+              th:if="${completedItemCount > 0}">
+            <button class="clear-completed">Clear completed</button>
+        </form>
+    </footer>
+</section>
+<footer class="info">
+    <p>Double-click to edit a todo</p>
+</footer>
+<script th:src="@{/webjars/todomvc-common/base.js}"></script>
+</body>
+</html>

example/kotlinlib/web/7-todo-spring-boot/src/com/example/TodomvcApplication.kt

@@ -0,0 +1,11 @@
+package com.example
+
+import org.springframework.boot.SpringApplication
+import org.springframework.boot.autoconfigure.SpringBootApplication
+
+@SpringBootApplication
+open class TodomvcApplication
+
+fun main(args: Array<String>) {
+    SpringApplication.run(TodomvcApplication::class.java, *args)
+}

example/kotlinlib/web/7-todo-spring-boot/src/com/example/todoitem/TodoItem.kt

@@ -0,0 +1,18 @@
+package com.example.todoitem
+
+import javax.persistence.Entity
+import javax.persistence.GeneratedValue
+import javax.persistence.Id
+import javax.validation.constraints.NotBlank
+
+@Entity
+data class TodoItem(
+    @Id
+    @GeneratedValue
+    val id: Long? = null,
+
+    @field:NotBlank
+    var title: String = "",
+
+    var completed: Boolean = false,
+)

example/kotlinlib/web/7-todo-spring-boot/src/com/example/todoitem/TodoItemNotFoundException.kt

@@ -0,0 +1,7 @@
+package com.example.todoitem
+
+import org.springframework.http.HttpStatus
+import org.springframework.web.bind.annotation.ResponseStatus
+
+@ResponseStatus(HttpStatus.NOT_FOUND)
+class TodoItemNotFoundException(itemId: Long) : RuntimeException("TodoItem itemId=$itemId not found")