Allow build to directly run under JDK 9 (elastic/x-pack-elasticsearch#2320)

With Gradle 4.1 and newer JDK versions, we can finally invoke Gradle directly using a JDK9 JAVA_HOME without requiring a JDK8 to "bootstrap" the build. As the thirdPartyAudit task runs within the JVM that Gradle runs in, it needs to be adapted now to be JDK9 aware.

Relates to elastic/elasticsearch#25859

Original commit: elastic/x-pack-elasticsearch@4bf266e0b0

plugin/build.gradle

@@ -290,10 +290,17 @@ thirdPartyAudit.excludes = [
     'com.sun.activation.registries.LineTokenizer',
     'com.sun.activation.registries.LogSupport',
     'com.sun.activation.registries.MailcapFile',
-    'com.sun.activation.registries.MailcapParseException',
     'com.sun.activation.registries.MailcapTokenizer',
     'com.sun.activation.registries.MimeTypeEntry',
     'com.sun.activation.registries.MimeTypeFile',
+    'javax.activation.MailcapCommandMap',
+    'javax.activation.MimetypesFileTypeMap',
+]
+
+// pulled in as external dependency to work on java 9
+if (JavaVersion.current() <= JavaVersion.VERSION_1_8) {
+  thirdPartyAudit.excludes += [
+    'com.sun.activation.registries.MailcapParseException',
     'javax.activation.ActivationDataFlavor',
     'javax.activation.CommandInfo',
     'javax.activation.CommandMap',
@@ -307,11 +314,9 @@ thirdPartyAudit.excludes = [
     'javax.activation.DataSourceDataContentHandler',
     'javax.activation.FileDataSource',
     'javax.activation.FileTypeMap',
-    'javax.activation.MailcapCommandMap',
     'javax.activation.MimeType',
     'javax.activation.MimeTypeParameterList',
     'javax.activation.MimeTypeParseException',
-    'javax.activation.MimetypesFileTypeMap',
     'javax.activation.ObjectDataContentHandler',
     'javax.activation.SecuritySupport$1',
     'javax.activation.SecuritySupport$2',
@@ -321,7 +326,8 @@ thirdPartyAudit.excludes = [
     'javax.activation.SecuritySupport',
     'javax.activation.URLDataSource',
     'javax.activation.UnsupportedDataTypeException'
-]
+  ]
+}
 
 run {
   setting 'xpack.ml.enabled', 'true'

plugin/ml-cpp-snapshot/build.gradle

@@ -21,6 +21,9 @@ buildscript {
   dependencies {
     classpath group: 'com.bettercloud', name: 'vault-java-driver', version:"1.1.0"
     classpath 'com.amazonaws:aws-java-sdk-s3:1.10.33'
+    if (JavaVersion.current() > JavaVersion.VERSION_1_8) {
+      classpath 'com.sun.xml.bind:jaxb-impl:2.2.3-1' // pulled in as external dependency to work on java 9
+    }
   }
 }
 
@@ -40,17 +43,17 @@ void checkJavaVersion() {
   final String javaVendor = System.getProperty('java.vendor')
   def matcher = javaVersion =~ /1\.8\.0(?:_(\d+))?/
   boolean matches = matcher.matches()
-  assert matches
-
-  final int update
-  if (matcher.group(1) == null) {
-    update = 0
-  } else {
-    update = matcher.group(1).toInteger()
-  }
-  if (update < 101) {
-    throw new GradleException("JDK ${javaVendor} ${javaVersion} does not have necessary root certificates " +
-            "(https://bugs.openjdk.java.net/browse/JDK-8154757), update your JDK to at least JDK 8u101+")
+  if (matches) {
+    final int update
+    if (matcher.group(1) == null) {
+      update = 0
+    } else {
+      update = matcher.group(1).toInteger()
+    }
+    if (update < 101) {
+      throw new GradleException("JDK ${javaVendor} ${javaVersion} does not have necessary root certificates " +
+              "(https://bugs.openjdk.java.net/browse/JDK-8154757), update your JDK to at least JDK 8u101+")
+    }
   }
 }