Unresolved symbol:mainClassName - spring-boot

Question

I have a SpringBoot project with the following build.gradle:
import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
plugins {
id("org.springframework.boot") version "2.7.0"
id("io.spring.dependency-management") version "1.0.9.RELEASE"
kotlin("jvm") version "1.7.0"
kotlin("plugin.spring") version "1.7.0"
kotlin("plugin.jpa") version "1.6.21"
id("org.flywaydb.flyway") version "6.4.4"
}
group = "com.planes"
version = "0.0.1-SNAPSHOT"
java.sourceCompatibility = JavaVersion.VERSION_1_8
repositories {
mavenCentral()
}
dependencies {
implementation("org.apache.tomcat.embed:tomcat-embed-jasper")
implementation("org.springframework.boot:spring-boot-starter-data-jpa")
implementation("org.springframework.boot:spring-boot-starter-validation")
implementation("org.springframework.boot:spring-boot-starter-security")
implementation("org.springframework.boot:spring-boot-starter-web")
implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
implementation("org.jetbrains.kotlin:kotlin-reflect")
implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
implementation("io.jsonwebtoken:jjwt:0.9.0")
implementation("org.postgresql:postgresql")
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core")
testImplementation("org.springframework.boot:spring-boot-starter-test") {
exclude(group = "org.junit.vintage", module = "junit-vintage-engine")
}
testImplementation("org.springframework.security:spring-security-test")
}
tasks.withType<Test> {
useJUnitPlatform()
}
tasks.withType<KotlinCompile> {
kotlinOptions {
freeCompilerArgs = listOf("-Xjsr305=strict")
jvmTarget = "1.8"
}
}
springBoot {
mainClassName = "com.planes.planesserver.DemoApplication"
}
When I run the Gradle Wrapper Task I get the following error: "Unresolved reference: mainClassName"
This happens after I updated SpringBoot from Version 2.2 to 2.7 and gradle from version 5 to version 6.9.3
In the previous configuration the project could compile just fine. Are there any adjustments I need to still make for this new configuration ?
Can anyone please give a suggestion ?

Answer 1

In Springboot 2.4 they changed the name and type of the main classname property, see in Springboot 2.4 Release notes:
You need to update your build script as follows :
springBoot {
// before springboot 2.4
// mainClassName = "com.planes.planesserver.DemoApplication"
// since springboot 2.4 :
mainClass.set( "com.planes.planesserver.DemoApplication")
}