Add Kotlin app with Spring Boot 3 and coroutines

.kotlin/errors/errors-1745213070779.log

@@ -0,0 +1,4 @@
+kotlin version: 2.0.21
+error message: The daemon has terminated unexpectedly on startup attempt #1 with error code: 0. The daemon process output:
+    1. Kotlin compile daemon is ready
+

.kotlin/errors/errors-1746001177744.log

@@ -0,0 +1,4 @@
+kotlin version: 2.0.21
+error message: The daemon has terminated unexpectedly on startup attempt #1 with error code: 0. The daemon process output:
+    1. Kotlin compile daemon is ready
+

buildSrc/build.gradle.kts

@@ -14,4 +14,8 @@ dependencies {
     implementation("de.thetaphi:forbiddenapis:3.9")
     implementation("com.github.spotbugs.snom:spotbugs-gradle-plugin:6.1.7")
     implementation("org.gradle:test-retry-gradle-plugin:1.6.2")
+    val kotlinVersion = "2.0.21"
+    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")
+    implementation("org.jetbrains.kotlin:kotlin-allopen:$kotlinVersion")
+    implementation("io.gitlab.arturbosch.detekt:detekt-gradle-plugin:1.23.6")
 }

buildSrc/src/main/kotlin/sb-ot-demo.java-compile.gradle.kts

@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2020-2025. Ivan Vakhrushev and others.
+ * https://github.com/mfvanek/spring-boot-open-telemetry-demo
+ *
+ * Licensed under the Apache License 2.0
+ */
+
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.check
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.jacocoTestCoverageVerification
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.jacocoTestReport
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.java
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.osdetector
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.test
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.testImplementation
+import gradle.kotlin.dsl.accessors._82e33fab8c067a1df5c2e280e32692b4.testRuntimeOnly
+
+plugins {
+    id("java")
+    id("jacoco")
+    id("com.google.osdetector")
+    id("org.gradle.test-retry")
+}
+dependencies {
+    testImplementation("org.assertj:assertj-core")
+    testImplementation("org.junit.jupiter:junit-jupiter-api")
+    testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+    // https://github.com/netty/netty/issues/11020
+    if (osdetector.arch == "aarch_64") {
+        testImplementation("io.netty:netty-all:4.1.104.Final")
+    }
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_17
+    targetCompatibility = JavaVersion.VERSION_17
+    withJavadocJar()
+    withSourcesJar()
+}
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(17)
+    }
+}
+
+tasks {
+    withType<JavaCompile>().configureEach {
+        options.compilerArgs.add("-parameters")
+        options.compilerArgs.add("--should-stop=ifError=FLOW")
+    }
+
+    test {
+        useJUnitPlatform()
+
+        finalizedBy(jacocoTestReport, jacocoTestCoverageVerification)
+        maxParallelForks = 1
+
+        retry {
+            maxRetries.set(2)
+            maxFailures.set(5)
+            failOnPassedAfterRetry.set(false)
+        }
+    }
+
+    jacocoTestCoverageVerification {
+        dependsOn(jacocoTestReport)
+        violationRules {
+            rule {
+                limit {
+                    counter = "CLASS"
+                    value = "MISSEDCOUNT"
+                    maximum = "0.0".toBigDecimal()
+                }
+            }
+            rule {
+                limit {
+                    counter = "METHOD"
+                    value = "MISSEDCOUNT"
+                    maximum = "2.0".toBigDecimal()
+                }
+            }
+            rule {
+                limit {
+                    counter = "LINE"
+                    value = "MISSEDCOUNT"
+                    maximum = "7.0".toBigDecimal()
+                }
+            }
+            rule {
+                limit {
+                    counter = "INSTRUCTION"
+                    value = "COVEREDRATIO"
+                    minimum = "0.93".toBigDecimal()
+                }
+            }
+            rule {
+                limit {
+                    counter = "BRANCH"
+                    value = "COVEREDRATIO"
+                    minimum = "0.66".toBigDecimal()
+                }
+            }
+        }
+    }
+
+    jacocoTestReport {
+        dependsOn(test)
+        reports {
+            xml.required.set(true)
+            html.required.set(true)
+        }
+    }
+
+    check {
+        dependsOn(jacocoTestCoverageVerification)
+    }
+}

buildSrc/src/main/kotlin/sb-ot-demo.java-conventions.gradle.kts

@@ -19,6 +19,7 @@ plugins {
     id("net.ltgt.errorprone")
     id("com.google.osdetector")
     id("org.gradle.test-retry")
+    id("sb-ot-demo.java-compile")
 }
 
 dependencies {
@@ -43,16 +44,6 @@ dependencies {
     spotbugsPlugins("com.mebigfatguy.sb-contrib:sb-contrib:7.6.9")
 }
 
-java {
-    toolchain {
-        languageVersion = JavaLanguageVersion.of(17)
-    }
-}
-
-jacoco {
-    toolVersion = "0.8.12"
-}
-
 checkstyle {
     toolVersion = "10.21.1"
     configFile = file("${rootDir}/config/checkstyle/checkstyle.xml")
@@ -84,77 +75,13 @@ tasks.withType<SpotBugsTask>().configureEach {
 
 tasks {
     withType<JavaCompile>().configureEach {
-        options.compilerArgs.add("-parameters")
-        options.compilerArgs.add("--should-stop=ifError=FLOW")
         options.errorprone {
             disableWarningsInGeneratedCode.set(true)
             disable("Slf4jLoggerShouldBeNonStatic")
         }
     }
 
     test {
-        useJUnitPlatform()
         dependsOn(checkstyleMain, checkstyleTest, pmdMain, pmdTest, spotbugsMain, spotbugsTest)
-        finalizedBy(jacocoTestReport, jacocoTestCoverageVerification)
-        maxParallelForks = 1
-
-        retry {
-            maxRetries.set(2)
-            maxFailures.set(5)
-            failOnPassedAfterRetry.set(false)
-        }
-    }
-
-    jacocoTestCoverageVerification {
-        dependsOn(jacocoTestReport)
-        violationRules {
-            rule {
-                limit {
-                    counter = "CLASS"
-                    value = "MISSEDCOUNT"
-                    maximum = "0.0".toBigDecimal()
-                }
-            }
-            rule {
-                limit {
-                    counter = "METHOD"
-                    value = "MISSEDCOUNT"
-                    maximum = "2.0".toBigDecimal()
-                }
-            }
-            rule {
-                limit {
-                    counter = "LINE"
-                    value = "MISSEDCOUNT"
-                    maximum = "7.0".toBigDecimal()
-                }
-            }
-            rule {
-                limit {
-                    counter = "INSTRUCTION"
-                    value = "COVEREDRATIO"
-                    minimum = "0.93".toBigDecimal()
-                }
-            }
-            rule {
-                limit {
-                    counter = "BRANCH"
-                    value = "COVEREDRATIO"
-                    minimum = "0.66".toBigDecimal()
-                }
-            }
-        }
-    }
-
-    jacocoTestReport {
-        dependsOn(test)
-        reports {
-            xml.required.set(true)
-            html.required.set(true)
-        }
-    }
-
-    check {
-        dependsOn(jacocoTestCoverageVerification)
     }
 }

buildSrc/src/main/kotlin/sb-ot-demo.kotlin-conventions.gradle.kts

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2020-2025. Ivan Vakhrushev and others.
+ * https://github.com/mfvanek/spring-boot-open-telemetry-demo
+ *
+ * Licensed under the Apache License 2.0
+ */
+
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+    id("java")
+    id("jacoco")
+    id("org.jetbrains.kotlin.jvm")
+    id("org.jetbrains.kotlin.plugin.spring")
+    id("io.gitlab.arturbosch.detekt")
+    id("sb-ot-demo.forbidden-apis")
+    id("sb-ot-demo.java-compile")
+}
+
+dependencies {
+    implementation("org.jetbrains.kotlin:kotlin-reflect")
+    //implementation("io.gitlab.arturbosch.detekt:detekt-formatting:1.23.6")
+    implementation("io.gitlab.arturbosch.detekt:detekt-rules-libraries:1.23.6")
+}
+
+tasks.withType<KotlinCompile> {
+    compilerOptions {
+        freeCompilerArgs.add("-Xjsr305=strict")
+        jvmTarget = JvmTarget.JVM_17
+    }
+}
+
+detekt {
+    toolVersion = "1.23.6"
+    config.setFrom(file("${rootDir}/config/detekt/detekt.yml"))
+    buildUponDefaultConfig = true
+}
+
+tasks {
+    withType<JavaCompile>().configureEach {
+        options.compilerArgs.add("-parameters")
+        options.compilerArgs.add("--should-stop=ifError=FLOW")
+    }
+
+    test {
+        testLogging.showStandardStreams = false // set to true for debug purposes
+    }
+}
+
+
+

config/detekt/detekt.yml

@@ -0,0 +1,7 @@
+performance:
+    SpreadOperator:
+        active: false
+
+style:
+    MaxLineLength:
+        maxLineLength: 200

db-migrations/build.gradle.kts

@@ -1,4 +1,6 @@
 plugins {
     id("java")
     id("sb-ot-demo.java-conventions")
+    id("sb-ot-demo.kotlin-conventions")
 }
+

settings.gradle.kts

@@ -1,8 +1,12 @@
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention") version "0.8.0"
+}
 rootProject.name = "spring-boot-open-telemetry-demo"
 include("spring-boot-3-demo-app")
 include("common-internal-bom")
 include("spring-boot-2-demo-app")
 include("db-migrations")
+include("spring-boot-3-demo-app-kotlin")
 
 dependencyResolutionManagement {
     versionCatalogs {
@@ -15,3 +19,4 @@ dependencyResolutionManagement {
         }
     }
 }
+

spring-boot-2-demo-app/build.gradle.kts

@@ -33,7 +33,9 @@ dependencies {
     implementation("org.springframework.boot:spring-boot-starter-jdbc")
     implementation("org.postgresql:postgresql")
     implementation("com.zaxxer:HikariCP")
-    implementation(project(":db-migrations"))
+    implementation(project(":db-migrations")){
+        exclude(group = "io.gitlab.arturbosch.detekt")
+    }
     implementation("org.liquibase:liquibase-core")
     implementation("com.github.blagerweij:liquibase-sessionlock")
     implementation("net.ttddyy:datasource-proxy:1.9") {