Fixed NPE issue with Metadata calls in SEA (#1130)

## Description
<!-- Provide a brief summary of the changes made and the issue they aim
to address.-->
Fixed NPE in metadata calls for SEA.
## Testing
<!-- Describe how the changes have been tested-->
Tested locally
## Additional Notes to the Reviewer
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understand the changes better. This could include challenges faced,
limitations, or compromises made during the development process.
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NO_CHANGELOG=true
Fixes
[PECOBLR-1372](https://databricks.atlassian.net/browse/PECOBLR-1372)


[PECOBLR-1372]:
https://databricks.atlassian.net/browse/PECOBLR-1372?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: msrathore-db

src/main/java/com/databricks/jdbc/dbclient/impl/sqlexec/DatabricksMetadataSdkClient.java

@@ -79,7 +79,7 @@ public DatabricksResultSet listSchemas(
       return metadataResultSetBuilder.getSchemasResult(getResultSet(SQL, session), catalog);
     } catch (SQLException e) {
       if (WildcardUtil.isNullOrWildcard(catalog)
-          && e.getSQLState().equals(PARSE_SYNTAX_ERROR_SQL_STATE)) {
+          && PARSE_SYNTAX_ERROR_SQL_STATE.equals(e.getSQLState())) {
         // This is a fallback for the case where the SQL command fails with "syntax error at or near
         // "ALL CATALOGS""
         // This is a known issue for older DBR versions
@@ -115,7 +115,7 @@ public DatabricksResultSet listTables(
       return metadataResultSetBuilder.getTablesResult(
           getResultSet(SQL, session), validatedTableTypes);
     } catch (SQLException e) {
-      if (e.getSQLState().equals(PARSE_SYNTAX_ERROR_SQL_STATE)
+      if (PARSE_SYNTAX_ERROR_SQL_STATE.equals(e.getSQLState())
           && (catalog == null || catalog.equals("*") || catalog.equals("%"))) {
         // Gracefully handles the case where an older DBSQL version doesn't support all catalogs in
         // the SHOW TABLES command.
@@ -247,7 +247,7 @@ public DatabricksResultSet listImportedKeys(
     try {
       return metadataResultSetBuilder.getImportedKeysResult(getResultSet(SQL, session));
     } catch (SQLException e) {
-      if (e.getSQLState().equals(PARSE_SYNTAX_ERROR_SQL_STATE)) {
+      if (PARSE_SYNTAX_ERROR_SQL_STATE.equals(e.getSQLState())) {
         // This is a workaround for the issue where the SQL command fails with "syntax error at or
         // near "foreign""
         LOGGER.debug("SQL command failed with syntax error. Returning empty result set.");
@@ -293,7 +293,7 @@ public DatabricksResultSet listCrossReferences(
       return metadataResultSetBuilder.getCrossReferenceKeysResult(
           getResultSet(SQL, session), parentCatalog, parentSchema, parentTable);
     } catch (SQLException e) {
-      if (e.getSQLState().equals(PARSE_SYNTAX_ERROR_SQL_STATE)) {
+      if (PARSE_SYNTAX_ERROR_SQL_STATE.equals(e.getSQLState())) {
         // This is a workaround for the issue where the SQL command fails with "syntax error at or
         // near "foreign""
         // This is a known issue in Databricks for older DBSQL versions

src/test/java/com/databricks/jdbc/dbclient/impl/sqlexec/DatabricksMetadataSdkClientTest.java

@@ -964,4 +964,125 @@ void testListSchemasWithMultipleCatalogSupportDisabled() throws SQLException {
     assertEquals(METADATA_STATEMENT_ID, actualResult.getStatementId());
     assertEquals(2, ((DatabricksResultSetMetaData) actualResult.getMetaData()).getTotalRows());
   }
+
+  /**
+   * Test that listTables handles SQLException with null SQL state without NPE. This tests the fix
+   * for the issue where e.getSQLState() could return null, causing NullPointerException when
+   * calling .equals() on it.
+   */
+  @Test
+  void testListTables_handlesNullSqlStateWithoutNPE() throws Exception {
+    // Create exception with null SQL state (simulating server response without structured SQL
+    // state)
+    DatabricksSQLException exception =
+        new DatabricksSQLException(
+            "[SCHEMA_NOT_FOUND] The schema cannot be found. SQLSTATE: 42704",
+            (String) null); // null SQL state
+
+    when(session.getComputeResource()).thenReturn(WAREHOUSE_COMPUTE);
+    IDatabricksConnectionContext mockContext = mock(IDatabricksConnectionContext.class);
+    when(mockContext.getEnableMultipleCatalogSupport()).thenReturn(true);
+    when(mockClient.getConnectionContext()).thenReturn(mockContext);
+
+    DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
+    when(mockClient.executeStatement(
+            "SHOW TABLES IN CATALOG ",
+            WAREHOUSE_COMPUTE,
+            new HashMap<>(),
+            StatementType.METADATA,
+            session,
+            null))
+        .thenThrow(exception);
+
+    // This should throw the original exception, not NPE
+    assertThrows(
+        DatabricksSQLException.class,
+        () -> metadataClient.listTables(session, "", null, null, null));
+  }
+
+  @Test
+  void testListSchemas_handlesNullSqlStateWithoutNPE() throws Exception {
+    DatabricksSQLException exception =
+        new DatabricksSQLException(
+            "syntax error at or near \"ALL CATALOGS\"", (String) null); // null SQL state
+
+    when(session.getComputeResource()).thenReturn(WAREHOUSE_COMPUTE);
+    IDatabricksConnectionContext mockContext = mock(IDatabricksConnectionContext.class);
+    when(mockContext.getEnableMultipleCatalogSupport()).thenReturn(true);
+    when(mockClient.getConnectionContext()).thenReturn(mockContext);
+
+    DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
+    when(mockClient.executeStatement(
+            "SHOW SCHEMAS IN ALL CATALOGS",
+            WAREHOUSE_COMPUTE,
+            new HashMap<>(),
+            StatementType.METADATA,
+            session,
+            null))
+        .thenThrow(exception);
+
+    // This should throw the original exception, not NPE
+    assertThrows(
+        DatabricksSQLException.class, () -> metadataClient.listSchemas(session, null, null));
+  }
+
+  @Test
+  void testListImportedKeys_handlesNullSqlStateWithoutNPE() throws Exception {
+    DatabricksSQLException exception =
+        new DatabricksSQLException(
+            "syntax error at or near \"foreign\"", (String) null); // null SQL state
+
+    when(session.getComputeResource()).thenReturn(WAREHOUSE_COMPUTE);
+    IDatabricksConnectionContext mockContext = mock(IDatabricksConnectionContext.class);
+    when(mockContext.getEnableMultipleCatalogSupport()).thenReturn(true);
+    when(mockClient.getConnectionContext()).thenReturn(mockContext);
+
+    DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
+    when(mockClient.executeStatement(
+            "SHOW FOREIGN KEYS IN CATALOG catalog1 IN SCHEMA testSchema IN TABLE testTable",
+            WAREHOUSE_COMPUTE,
+            new HashMap<>(),
+            StatementType.METADATA,
+            session,
+            null))
+        .thenThrow(exception);
+
+    // This should throw the original exception, not NPE
+    assertThrows(
+        DatabricksSQLException.class,
+        () -> metadataClient.listImportedKeys(session, TEST_CATALOG, TEST_SCHEMA, TEST_TABLE));
+  }
+
+  @Test
+  void testListCrossReferences_handlesNullSqlStateWithoutNPE() throws Exception {
+    DatabricksSQLException exception =
+        new DatabricksSQLException(
+            "syntax error at or near \"foreign\"", (String) null); // null SQL state
+
+    when(session.getComputeResource()).thenReturn(WAREHOUSE_COMPUTE);
+    when(mockClient.getConnectionContext()).thenReturn(mock(IDatabricksConnectionContext.class));
+
+    DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
+    when(mockClient.executeStatement(
+            "SHOW FOREIGN KEYS IN CATALOG catalog1 IN SCHEMA testSchema IN TABLE testTable",
+            WAREHOUSE_COMPUTE,
+            new HashMap<>(),
+            StatementType.METADATA,
+            session,
+            null))
+        .thenThrow(exception);
+
+    // This should throw the original exception, not NPE
+    assertThrows(
+        DatabricksSQLException.class,
+        () ->
+            metadataClient.listCrossReferences(
+                session,
+                "parentCatalog",
+                "parentSchema",
+                "parentTable",
+                TEST_CATALOG,
+                TEST_SCHEMA,
+                TEST_TABLE));
+  }
 }