无法为扩展名“ application”设置未知属性“ mainClass”

gradle 6.1版

在我的build.gradle中:

plugins {
    id 'application'
}

application {
    mainClass = 'com.mytestproject.Main'
}

java {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8
}

group 'com.mytestproject'
version '1.0-SNAPSHOT'

repositories {
    mavenCentral()
}

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
}

但是在控制台中我运行

./gradlew汇编

但是我在这一行中出错:

application {
    mainClass = 'com.mytestproject.Main'
}

这里详细说明:

./gradlew汇编

FAILURE: Build failed with an exception.

* Where:
Build file '/com/myproject/build.gradle' line: 6

* What went wrong:
A problem occurred evaluating root project 'JavaTestProject'.
> Could not set unknown property 'mainClass' for extension 'application' of type org.gradle.api.plugins.internal.DefaultJavaApplication.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 484ms