check for Oracle account and report if not found

core/src/main/java/hudson/tools/JDKInstaller.java

@@ -49,6 +49,7 @@ import org.apache.commons.io.IOUtils;
 import org.kohsuke.stapler.DataBoundConstructor;
 import org.kohsuke.stapler.HttpResponse;
 import org.kohsuke.stapler.QueryParameter;
+import org.kohsuke.stapler.Stapler;
 
 import javax.servlet.ServletException;
 import java.io.ByteArrayInputStream;
@@ -582,12 +583,11 @@ public class JDKInstaller extends ToolInstaller {
         }
 
         public FormValidation doCheckId(@QueryParameter String value) {
-            if (Util.fixEmpty(value) == null) {
+            if (Util.fixEmpty(value) == null)
                 return FormValidation.error(Messages.JDKInstaller_DescriptorImpl_doCheckId()); // improve message
-            } else {
-                // XXX further checks? 
-                return FormValidation.ok();
-            }
+            if (username==null || password==null)
+                return FormValidation.errorWithMarkup(Messages.JDKInstaller_RequireOracleAccount(Stapler.getCurrentRequest().getContextPath()+getDescriptorUrl()));
+            return FormValidation.ok();
         }
 
         /**

core/src/main/resources/hudson/tools/Messages.properties

@@ -25,6 +25,7 @@ CommandInstaller.DescriptorImpl.displayName=Run Command
 CommandInstaller.no_command=Must provide a command to run.
 CommandInstaller.no_toolHome=Must provide a tool home directory.
 JDKInstaller.FailedToInstallJDK=Failed to install JDK. Exit code={0}
+JDKInstaller.RequireOracleAccount=Installing JDK requires Oracle account. <a href="{0}">Please enter your username/password</a>
 JDKInstaller.UnableToInstallUntilLicenseAccepted=Unable to auto-install JDK until the license is accepted.
 ZipExtractionInstaller.DescriptorImpl.displayName=Extract *.zip/*.tar.gz
 ZipExtractionInstaller.bad_connection=Server rejected connection.