KAFKA-10787: Add import ordering checkstyle rule and configure an automatic formatter

build.gradle

@@ -47,7 +47,7 @@ plugins {
   // Updating the shadow plugin version to 8.1.1 causes issue with signing and publishing the shadowed
   // artifacts - see https://github.com/johnrengelman/shadow/issues/901
   id 'com.github.johnrengelman.shadow' version '8.1.0' apply false
-  id 'com.diffplug.spotless' version '6.14.0' apply false // 6.14.1 and newer require Java 11 at compile time, so we can't upgrade until AK 4.0
+  id 'com.diffplug.spotless' version "${spotlessVersion}" apply false
 }
 
 ext {
@@ -196,6 +196,19 @@ def determineCommitId() {
   }
 }
 
+def spotlessApplyModules = ['']
+
+def configureSpotless = { project ->
+  project.apply plugin: 'com.diffplug.spotless'
+
+  project.spotless {
+    java {
+      importOrder('kafka', 'org.apache.kafka', 'com', 'net', 'org', 'java', 'javax', '', '\\#')
+      removeUnusedImports()
+    }
+  }
+}
+
 apply from: file('wrapper.gradle')
 
 if (repo != null) {
@@ -787,6 +800,12 @@ subprojects {
     skipProjects = [ ":jmh-benchmarks", ":trogdor" ]
     skipConfigurations = [ "zinc" ]
   }
+
+  afterEvaluate {
+    if (project.name in spotlessApplyModules) {
+      configureSpotless(project)
+    }
+  }
 }
 
 gradle.taskGraph.whenReady { taskGraph ->
@@ -1007,7 +1026,7 @@ project(':core') {
     testImplementation libs.junitJupiter
     testImplementation libs.slf4jlog4j
     testImplementation libs.caffeine
-    
+
     generator project(':generator')
   }
 

checkstyle/checkstyle.xml

@@ -82,6 +82,14 @@
       <property name="file" value="${config_loc}/${importControlFile}"/>
     </module>
 
+    <module name="ImportOrder">
+      <property name="groups" value="kafka,org.apache.kafka,com,net,org,java,javax"/>
+      <property name="ordered" value="true"/>
+      <property name="separated" value="true"/>
+      <property name="option" value="bottom"/>
+      <property name="sortStaticImportsAlphabetically" value="true"/>
+    </module>
+
     <!-- whitespace -->
     <module name="GenericWhitespace"/>
     <module name="NoWhitespaceBefore"/>

checkstyle/suppressions.xml

@@ -361,4 +361,7 @@
     <suppress checks="(ClassDataAbstractionCoupling|ClassFanOutComplexity)"
               files="(ReplicaFetcherThreadBenchmark).java"/>
 
+    <!--import order -->
+    <suppress checks="ImportOrder" files="^*$"/>
+
 </suppressions>

gradle.properties

@@ -28,6 +28,8 @@ scalaVersion=2.13.14
 # Adding swaggerVersion in gradle.properties to have a single version in place for swagger
 # New version of Swagger 2.2.14 requires minimum JDK 11.
 swaggerVersion=2.2.8
+# 6.14.0 and newer are need for java 11
+spotlessVersion=6.13.0
 task=build
 org.gradle.jvmargs=-Xmx2g -Xss4m -XX:+UseParallelGC
 org.gradle.parallel=true