Updated Gradle configuration for Spigot 1.17 and added support for using the so-called "Mojang Mappings" via the use of a third-party plugin (https://www.spigotmc.org/threads/1-17-mappings-with-gradle.511184/).

build.gradle

@@ -1,23 +1,15 @@
 plugins {
     id 'java-library'
+    id 'com.github.yannicklamprecht.spigot.tools' version '1.0.1'
 }
 
 java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-    targetCompatibility = JavaVersion.VERSION_1_8
+    sourceCompatibility = JavaVersion.VERSION_16
+    targetCompatibility = JavaVersion.VERSION_16
 }
 
 repositories {
-    mavenCentral() // This is needed for dependencies.
-    /*
-	   As Spigot-API depends on the Bungeecord ChatComponent-API,
-	   we need to add the Sonatype OSS repository, as Gradle,
-	   in comparison to maven, doesn't want to understand the ~/.m2
-	   directory unless added using mavenLocal(). Maven usually just gets
-	   it from there, as most people have run the BuildTools at least once.
-	   This is therefore not needed if you're using the full Spigot/CraftBukkit,
-	   or if you're using the Bukkit API.
-    */
+    mavenCentral()
     maven { url = 'https://oss.sonatype.org/content/repositories/snapshots' }
     maven { url = 'https://hub.spigotmc.org/nexus/content/repositories/snapshots/' }
     mavenLocal() // This is needed for CraftBukkit and Spigot.
@@ -29,7 +21,7 @@ repositories {
 }
 
 dependencies {
-    compileOnly 'org.spigotmc:spigot:1.16.5-R0.1-SNAPSHOT'  // The full Spigot server with no shadowing. Requires mavenLocal.
+    compileOnly 'org.spigotmc:spigot:1.17-R0.1-SNAPSHOT:remapped-mojang'
     implementation name: 'Factions'
     implementation name: 'GriefPrevention'
     implementation name: 'MassiveCore'
@@ -39,4 +31,12 @@ dependencies {
     implementation name: 'Towny'
     implementation name: 'WorldEdit'
     implementation name: 'WorldGuard'
+}
+
+tasks {
+	spigotTools {
+		mojangMapped.set(true)
+		version.set("1.17")
+		outputClassifier.set("spigot-mapped")
+	}
 }

settings.gradle

@@ -7,4 +7,14 @@
  * in the user manual at https://docs.gradle.org/6.7/userguide/multi_project_builds.html
  */
 
-rootProject.name = 'Herobrine 2'
+pluginManagement {
+	repositories {
+		maven {
+			name = "eldonexus"
+			url = "https://eldonexus.de/repository/maven-releases/"
+		}
+		gradlePluginPortal()
+	}
+}
+
+rootProject.name = 'Herobrine 2'