fix(sql-execute): fall back to exception type when error message is null

SqlExecuteNode#executeSqlQuery reads e.getMessage() straight into both the
user-facing streamed text ("SQL执行失败: " + errorMessage) and
SqlRetryDto.sqlExecute(). NPE, StackOverflowError and several JDBC driver
wrappers carry a null message, so the UI rendered the literal
"SQL执行失败: null" and the retry reason stored null.

Fall back to the exception class name when the message is blank, so the
user always sees an actionable reason. The logged stack trace is
unchanged.

Add a regression test that throws a message-less RuntimeException and
asserts no "null" leaks into the streamed text while the failure notice
and retry reason are still produced.

Author: ydflow

data-agent-management/src/main/java/com/alibaba/cloud/ai/dataagent/workflow/node/SqlExecuteNode.java

@@ -152,7 +152,9 @@ private Map<String, Object> executeSqlQuery(OverAllState state, Integer currentS
 			.flatMapMany(executed -> Flux.concat(baseResultResponses(executed.resultSet()),
 					chartUpdateResponses(state, executed.resultSet())))
 			.onErrorResume(e -> {
-				String errorMessage = e.getMessage();
+				// NPE / StackOverflowError and several JDBC wrappers carry a null message;
+				// fall back to the exception type so the user never sees the literal "null"
+				String errorMessage = StringUtils.isNotBlank(e.getMessage()) ? e.getMessage() : e.getClass().getName();
 				log.error("SQL execution failed - SQL as follows: \n {} \n ", sqlQuery, e);
 				result.put(SQL_REGENERATE_REASON, SqlRetryDto.sqlExecute(errorMessage));
 				return Flux.just(ChatResponseUtil.createResponse("SQL执行失败: " + errorMessage));

data-agent-management/src/test/java/com/alibaba/cloud/ai/dataagent/workflow/node/sql/SqlExecuteNodeTest.java

@@ -237,6 +237,26 @@ void apply_sqlExecutionError_setsRetryReason() throws Exception {
 		assertFalse(execution.finalResult().containsKey(PLAN_CURRENT_STEP));
 	}
 
+	@Test
+	void apply_sqlExecutionErrorWithoutMessage_doesNotLeakNullIntoUserFacingText() throws Exception {
+		OverAllState state = createTestState();
+		setupBasicState(state);
+		setupBasicMocks();
+
+		// NPE / StackOverflowError and several JDBC wrappers carry a null message
+		when(accessor.executeSqlAndReturnObject(any(), any())).thenThrow(new RuntimeException((String) null));
+
+		NodeExecution execution = execute(sqlExecuteNode.apply(state), SQL_EXECUTE_NODE_OUTPUT);
+
+		String streamed = execution.streamedText();
+		assertFalse(streamed.contains("null"),
+				"user-facing text must not leak the literal 'null', was: " + streamed);
+		assertTrue(streamed.contains("SQL执行失败"), "failure notice must still be emitted, was: " + streamed);
+		SqlRetryDto retryReason = (SqlRetryDto) execution.finalResult().get(SQL_REGENERATE_REASON);
+		assertNotNull(retryReason);
+		assertTrue(retryReason.sqlExecuteFail());
+	}
+
 	@Test
 	void apply_connectionFailure_throwsException() throws Exception {
 		OverAllState state = createTestState();