skip dataflint UI on databricks spark 4 to avoid jakarta.servlet crash

spark-plugin/plugin/src/main/scala/org/apache/spark/dataflint/DataflintSparkUICommonLoader.scala

@@ -112,6 +112,10 @@ class DataflintSparkUICommonInstaller extends Logging {
       logInfo("DataFlint UI is already installed, skipping installation...")
       return ui.webUrl
     }
+    if (!pageFactory.isUISupported(ui)) {
+      logWarning("DataFlint UI is not supported in this environment, skipping UI installation; listeners will still run")
+      return ui.webUrl
+    }
     pageFactory.addStaticHandler(ui, "io/dataflint/spark/static/ui", ui.basePath + "/dataflint")
     val dataflintStore = new DataflintStore(store = ui.store.store)
     val tab = pageFactory.createDataFlintTab(ui)

spark-plugin/plugin/src/main/scala/org/apache/spark/dataflint/api/DataflintPageFactory.scala

@@ -27,6 +27,8 @@ abstract class DataflintPageFactory {
   def createSQLStagesRddPage(ui: SparkUI): WebUIPage
 
   def addStaticHandler(ui: SparkUI, resourceBase: String, contextPath: String): Unit
-  
+
   def getTabs(ui: SparkUI): Seq[WebUITab]
+
+  def isUISupported(ui: SparkUI): Boolean = true
 }

spark-plugin/pluginspark4/src/main/scala/org/apache/spark/dataflint/api/Spark4PageFactory.scala

@@ -44,8 +44,15 @@ class Spark4PageFactory extends DataflintPageFactory {
   override def addStaticHandler(ui: SparkUI, resourceBase: String, contextPath: String): Unit = {
     DataflintJettyUtils.addStaticHandler(ui, resourceBase, contextPath)
   }
-  
+
   override def getTabs(ui: SparkUI): Seq[WebUITab] = {
     ui.getTabs.toSeq
   }
+
+  // Databricks Runtime 17.3 (Spark 4 based) ships javax.servlet instead of jakarta.servlet,
+  // so any access to jakarta.servlet.* in this module crashes with NoClassDefFoundError.
+  // Skip the entire DataFlint UI on Databricks; listeners (data export) still run.
+  override def isUISupported(ui: SparkUI): Boolean = {
+    !ui.conf.getOption("spark.databricks.clusterUsageTags.cloudProvider").isDefined
+  }
 }