feat: Add method to construct InputTableUpdater from Table

engine/table/src/main/java/io/deephaven/engine/table/impl/util/BaseArrayBackedInputTable.java

@@ -54,7 +54,7 @@ public BaseArrayBackedInputTable(TrackingRowSet rowSet, Map<String, ? extends Co
     }
 
     public InputTableUpdater inputTable() {
-        return (InputTableUpdater) getAttribute(Table.INPUT_TABLE_ATTRIBUTE);
+        return InputTableUpdater.from(this);
     }
 
     public Table readOnlyCopy() {

engine/table/src/main/java/io/deephaven/engine/util/input/InputTableUpdater.java

@@ -21,6 +21,19 @@
  */
 public interface InputTableUpdater {
 
+    /**
+     * Get the input table updater from the given {@code table}, or {@code null} if the input table updater is not set
+     * or is the wrong type.
+     * 
+     * @param table the table
+     * @return the input table updater
+     * @see Table#INPUT_TABLE_ATTRIBUTE
+     */
+    static InputTableUpdater from(Table table) {
+        final Object obj = table.getAttribute(Table.INPUT_TABLE_ATTRIBUTE);
+        return obj instanceof InputTableUpdater ? (InputTableUpdater) obj : null;
+    }
+
     /**
      * Gets the names of the key columns.
      *

engine/table/src/test/java/io/deephaven/engine/table/impl/util/TestKeyedArrayBackedInputTable.java

@@ -43,7 +43,7 @@ public void testSimple() throws Exception {
 
         assertTableEquals(input, kabut);
 
-        final InputTableUpdater inputTableUpdater = (InputTableUpdater) kabut.getAttribute(Table.INPUT_TABLE_ATTRIBUTE);
+        final InputTableUpdater inputTableUpdater = InputTableUpdater.from(kabut);
         TestCase.assertNotNull(inputTableUpdater);
 
         final Table input2 = TableTools.newTable(stringCol("Name", "Randy"), stringCol("Employer", "USGS"));
@@ -101,8 +101,7 @@ public void testAppendOnly() throws Exception {
 
         assertTableEquals(input, aoabmt);
 
-        final InputTableUpdater inputTableUpdater =
-                (InputTableUpdater) aoabmt.getAttribute(Table.INPUT_TABLE_ATTRIBUTE);
+        final InputTableUpdater inputTableUpdater = InputTableUpdater.from(aoabmt);
         TestCase.assertNotNull(inputTableUpdater);
 
         final Table input2 =
@@ -127,7 +126,7 @@ public void testFilteredAndSorted() throws Exception {
 
         final Table fs = kabut.where("Name.length() == 4").sort("Name");
 
-        final InputTableUpdater inputTableUpdater = (InputTableUpdater) fs.getAttribute(Table.INPUT_TABLE_ATTRIBUTE);
+        final InputTableUpdater inputTableUpdater = InputTableUpdater.from(fs);
         TestCase.assertNotNull(inputTableUpdater);
 
         final Table delete = TableTools.newTable(stringCol("Name", "Fred"));
@@ -149,7 +148,7 @@ public void testAddBack() throws Exception {
 
         assertTableEquals(input, kabut);
 
-        final InputTableUpdater inputTableUpdater = (InputTableUpdater) kabut.getAttribute(Table.INPUT_TABLE_ATTRIBUTE);
+        final InputTableUpdater inputTableUpdater = InputTableUpdater.from(kabut);
         TestCase.assertNotNull(inputTableUpdater);
 
         final Table input2 =

py/server/deephaven/table_factory.py

@@ -26,7 +26,6 @@
 _JKeyedArrayBackedInputTable = jpy.get_type("io.deephaven.engine.table.impl.util.KeyedArrayBackedInputTable")
 _JTableDefinition = jpy.get_type("io.deephaven.engine.table.TableDefinition")
 _JTable = jpy.get_type("io.deephaven.engine.table.Table")
-_J_INPUT_TABLE_ATTRIBUTE = _JTable.INPUT_TABLE_ATTRIBUTE
 _J_InputTableUpdater = jpy.get_type("io.deephaven.engine.util.input.InputTableUpdater")
 _JRingTableTools = jpy.get_type("io.deephaven.engine.table.impl.sources.ring.RingTableTools")
 _JSupplier = jpy.get_type('java.util.function.Supplier')
@@ -247,11 +246,9 @@ class InputTable(Table):
 
     def __init__(self, j_table: jpy.JType):
         super().__init__(j_table)
-        self.j_input_table = self.j_table.getAttribute(_J_INPUT_TABLE_ATTRIBUTE)
+        self.j_input_table = getattr(_J_InputTableUpdater, "from")(self.j_table)
         if not self.j_input_table:
             raise DHError("the provided table input is not suitable for input tables.")
-        if not _J_InputTableUpdater.jclass.isInstance(self.j_input_table):
-            raise DHError("the provided table's InputTable attribute type is not of InputTableUpdater type.")
 
     def add(self, table: Table) -> None:
         """Synchronously writes rows from the provided table to this input table. If this is a keyed input table,

py/server/tests/test_table_factory.py

@@ -380,7 +380,7 @@ def test_input_table(self):
 
             with self.assertRaises(DHError) as cm:
                 InputTable(place_holder_input_table)
-            self.assertIn("not of InputTableUpdater type", str(cm.exception))
+            self.assertIn("the provided table input is not suitable for input tables.", str(cm.exception))
 
             self.assertTrue(isinstance(_wrapper.wrap_j_object(place_holder_input_table), Table))