title: Task :compileKotlin FAILED. Unresolved reference: web, Unresolved reference: GetMapping
body: <p>I asked this question.</p>
  
  <p><a href="https://stackoverflow.com/questions/58579752/how-to-start-the-web-application-with-spring-boot-and-kotlin">gradle - How to start the web application with Spring Boot and Kotlin - Stack Overflow</a></p>
  
  <p>I got an error:</p>
  
  <pre><code>% ./gradlew bootRun --stacktrace
  
  &gt; Task :compileKotlin FAILED
  e: /Users/shingonakanishi/Documents/src/spring/blog/blog/src/main/kotlin/com/example/blog/HtmlController.kt: (6, 28): Unresolved reference: web
  e: /Users/shingonakanishi/Documents/src/spring/blog/blog/src/main/kotlin/com/example/blog/HtmlController.kt: (11, 4): Unresolved reference: GetMapping
  
  FAILURE: Build failed with an exception.
  
  * What went wrong:
  Execution failed for task ':compileKotlin'.
  &gt; Compilation error. See log for more details
  
  * Try:
  Run with --info or --debug option to get more log output. Run with --scan to get full insights.
  
  * Exception is:
  org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':compileKotlin'.
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.accept(ExecuteActionsTaskExecuter.java:166)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.accept(ExecuteActionsTaskExecuter.java:163)
          at org.gradle.internal.Try$Failure.ifSuccessfulOrElse(Try.java:191)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:156)
          at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:62)
          at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:108)
          at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionOutputsTaskExecuter.execute(ResolveBeforeExecutionOutputsTaskExecuter.java:67)
          at org.gradle.api.internal.tasks.execution.ResolveAfterPreviousExecutionStateTaskExecuter.execute(ResolveAfterPreviousExecutionStateTaskExecuter.java:46)
          at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:94)
          at org.gradle.api.internal.tasks.execution.FinalizePropertiesTaskExecuter.execute(FinalizePropertiesTaskExecuter.java:46)
          at org.gradle.api.internal.tasks.execution.ResolveTaskExecutionModeExecuter.execute(ResolveTaskExecutionModeExecuter.java:95)
          at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:57)
          at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:56)
          at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:36)
          at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.executeTask(EventFiringTaskExecuter.java:77)
          at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:55)
          at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:52)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:416)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:406)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor.call(DefaultBuildOperationExecutor.java:102)
          at org.gradle.internal.operations.DelegatingBuildOperationExecutor.call(DelegatingBuildOperationExecutor.java:36)
          at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:52)
          at org.gradle.execution.plan.LocalTaskNodeExecutor.execute(LocalTaskNodeExecutor.java:43)
          at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:355)
          at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:343)
          at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:336)
          at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:322)
          at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:134)
          at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:129)
          at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:202)
          at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:193)
          at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:129)
          at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
          at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
          at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
  Caused by: org.gradle.api.GradleException: Compilation error. See log for more details
          at org.jetbrains.kotlin.gradle.tasks.TasksUtilsKt.throwGradleExceptionIfError(tasksUtils.kt:16)
          at org.jetbrains.kotlin.gradle.tasks.KotlinCompile.processCompilerExitCode(Tasks.kt:441)
          at org.jetbrains.kotlin.gradle.tasks.KotlinCompile.callCompiler$kotlin_gradle_plugin(Tasks.kt:403)
          at org.jetbrains.kotlin.gradle.tasks.KotlinCompile.callCompiler$kotlin_gradle_plugin(Tasks.kt:297)
          at org.jetbrains.kotlin.gradle.tasks.AbstractKotlinCompile.execute(Tasks.kt:259)
          at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
          at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
          at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
          at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:103)
          at org.gradle.api.internal.project.taskfactory.IncrementalTaskInputsTaskAction.doExecute(IncrementalTaskInputsTaskAction.java:47)
          at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:42)
          at org.gradle.api.internal.project.taskfactory.AbstractIncrementalTaskAction.execute(AbstractIncrementalTaskAction.java:25)
          at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:28)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$5.run(ExecuteActionsTaskExecuter.java:476)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:402)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:394)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
          at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:92)
          at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:461)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:444)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.access$200(ExecuteActionsTaskExecuter.java:93)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$TaskExecution.execute(ExecuteActionsTaskExecuter.java:237)
          at org.gradle.internal.execution.steps.ExecuteStep.lambda$execute$0(ExecuteStep.java:32)
          at org.gradle.internal.execution.steps.ExecuteStep.execute(ExecuteStep.java:32)
          at org.gradle.internal.execution.steps.ExecuteStep.execute(ExecuteStep.java:26)
          at org.gradle.internal.execution.steps.CleanupOutputsStep.execute(CleanupOutputsStep.java:58)
          at org.gradle.internal.execution.steps.CleanupOutputsStep.execute(CleanupOutputsStep.java:35)
          at org.gradle.internal.execution.steps.ResolveInputChangesStep.execute(ResolveInputChangesStep.java:48)
          at org.gradle.internal.execution.steps.ResolveInputChangesStep.execute(ResolveInputChangesStep.java:33)
          at org.gradle.internal.execution.steps.CancelExecutionStep.execute(CancelExecutionStep.java:39)
          at org.gradle.internal.execution.steps.TimeoutStep.executeWithoutTimeout(TimeoutStep.java:73)
          at org.gradle.internal.execution.steps.TimeoutStep.execute(TimeoutStep.java:54)
          at org.gradle.internal.execution.steps.CatchExceptionStep.execute(CatchExceptionStep.java:35)
          at org.gradle.internal.execution.steps.CreateOutputsStep.execute(CreateOutputsStep.java:51)
          at org.gradle.internal.execution.steps.SnapshotOutputsStep.execute(SnapshotOutputsStep.java:45)
          at org.gradle.internal.execution.steps.SnapshotOutputsStep.execute(SnapshotOutputsStep.java:31)
          at org.gradle.internal.execution.steps.CacheStep.executeWithoutCache(CacheStep.java:208)
          at org.gradle.internal.execution.steps.CacheStep.execute(CacheStep.java:70)
          at org.gradle.internal.execution.steps.CacheStep.execute(CacheStep.java:45)
          at org.gradle.internal.execution.steps.BroadcastChangingOutputsStep.execute(BroadcastChangingOutputsStep.java:49)
          at org.gradle.internal.execution.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:43)
          at org.gradle.internal.execution.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:32)
          at org.gradle.internal.execution.steps.RecordOutputsStep.execute(RecordOutputsStep.java:38)
          at org.gradle.internal.execution.steps.RecordOutputsStep.execute(RecordOutputsStep.java:24)
          at org.gradle.internal.execution.steps.SkipUpToDateStep.executeBecause(SkipUpToDateStep.java:96)
          at org.gradle.internal.execution.steps.SkipUpToDateStep.lambda$execute$0(SkipUpToDateStep.java:89)
          at org.gradle.internal.execution.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:54)
          at org.gradle.internal.execution.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:38)
          at org.gradle.internal.execution.steps.ResolveChangesStep.execute(ResolveChangesStep.java:76)
          at org.gradle.internal.execution.steps.ResolveChangesStep.execute(ResolveChangesStep.java:37)
          at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsFinishedStep.execute(MarkSnapshottingInputsFinishedStep.java:36)
          at org.gradle.internal.execution.steps.legacy.MarkSnapshottingInputsFinishedStep.execute(MarkSnapshottingInputsFinishedStep.java:26)
          at org.gradle.internal.execution.steps.ResolveCachingStateStep.execute(ResolveCachingStateStep.java:90)
          at org.gradle.internal.execution.steps.ResolveCachingStateStep.execute(ResolveCachingStateStep.java:48)
          at org.gradle.internal.execution.steps.CaptureStateBeforeExecutionStep.execute(CaptureStateBeforeExecutionStep.java:69)
          at org.gradle.internal.execution.steps.CaptureStateBeforeExecutionStep.execute(CaptureStateBeforeExecutionStep.java:47)
          at org.gradle.internal.execution.impl.DefaultWorkExecutor.execute(DefaultWorkExecutor.java:33)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:140)
          ... 34 more
  
  
  * Get more help at https://help.gradle.org
  
  Deprecated Gradle features were used in this build, making it incompatible with Gradle 6.0.
  Use '--warning-mode all' to show the individual deprecation warnings.
  </code></pre>
  
  <p>My <code>HtmlController.kt</code> same as <a href="https://spring.io/guides/tutorials/spring-boot-kotlin/" rel="nofollow noreferrer">Tutorial · Building web applications with Spring Boot and Kotlin</a>. Why does this error occur? I'm writing the controller as the tutorial.</p>
  
  <p>Is the import target different?
  Or is the gradle version different?</p>
  
  <p>HtmlController:</p>
  
  <pre><code>package com.example.blog
  
  import org.springframework.stereotype.Controller
  import org.springframework.ui.Model
  import org.springframework.ui.set
  import org.springframework.web.bind.annotation.GetMapping
  
  @Controller
  class HtmlController {
  
    @GetMapping("/")
    fun blog(model: Model): String {
      model["title"] = "Blog"
      return "blog"
    }
  
  }
  </code></pre>
  
  <p>build.gradle.kts:</p>
  
  <pre><code>import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
  
  plugins {
      id("org.springframework.boot") version "2.1.9.RELEASE"
      id("io.spring.dependency-management") version "1.0.8.RELEASE"
      kotlin("jvm") version "1.2.71"
      kotlin("plugin.spring") version "1.2.71"
  }
  
  group = "com.example"
  version = "0.0.1-SNAPSHOT"
  java.sourceCompatibility = JavaVersion.VERSION_1_8
  
  repositories {
      mavenCentral()
  }
  
  dependencies {
      implementation("org.springframework.boot:spring-boot-starter")
      implementation("org.jetbrains.kotlin:kotlin-reflect")
      implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
      testImplementation("org.springframework.boot:spring-boot-starter-test")
  }
  
  tasks.withType&lt;KotlinCompile&gt; {
      kotlinOptions {
          freeCompilerArgs = listOf("-Xjsr305=strict")
          jvmTarget = "1.8"
      }
  }
  </code></pre>