fix(finance): stabilize settlement idempotency request hashes

finance/src/main/java/com/baiyue/finance/service/FinanceSettlementService.java

@@ -12,6 +12,7 @@ import com.baiyue.finance.dto.FinanceSettlementDtos.SettlementActionRequest;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import org.slf4j.MDC;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.support.GeneratedKeyHolder;
@@ -523,10 +524,13 @@ public class FinanceSettlementService {
         return documentNumbers.next("PAY");
     }
 
+    /** 固定映射键序，避免 JVM 重启改变 Map.of 遍历顺序而误拒绝原请求。 */
     private String hash(Object value) {
         try {
+            String canonical = objectMapper.writer()
+                .with(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS).writeValueAsString(value);
             return HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256")
-                .digest(json(value).getBytes(StandardCharsets.UTF_8)));
+                .digest(canonical.getBytes(StandardCharsets.UTF_8)));
         } catch (Exception failure) {
             throw error("FIN_001", "幂等请求哈希失败");
         }

finance/src/test/java/com/baiyue/finance/FinanceSettlementRequestHashTest.java

@@ -0,0 +1,39 @@
+package com.baiyue.finance;
+
+import com.baiyue.finance.service.FinanceSettlementService;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Test;
+import org.springframework.test.util.ReflectionTestUtils;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class FinanceSettlementRequestHashTest {
+    /** 模拟不同 JVM 的 Map 遍历顺序；同一付款请求必须得到相同摘要。 */
+    @Test
+    void equivalentRequestsIgnoreMapIterationOrderButDetectChangedPayment() {
+        var service = new FinanceSettlementService(null, new ObjectMapper(), null, null, null);
+        Map<String, Object> body = new LinkedHashMap<>();
+        body.put("amount", 190); body.put("expectedVersion", 0);
+        Map<String, Object> first = new LinkedHashMap<>();
+        first.put("path", "/settlements/202/transactions"); first.put("method", "POST");
+        first.put("customerId", 10L); first.put("body", body);
+        Map<String, Object> reversedBody = new LinkedHashMap<>();
+        reversedBody.put("expectedVersion", 0); reversedBody.put("amount", 190);
+        Map<String, Object> second = new LinkedHashMap<>();
+        second.put("body", reversedBody); second.put("customerId", 10L);
+        second.put("method", "POST"); second.put("path", "/settlements/202/transactions");
+
+        String original = ReflectionTestUtils.invokeMethod(service, "hash", first);
+        String reordered = ReflectionTestUtils.invokeMethod(service, "hash", second);
+        assertThat(reordered).isEqualTo(original);
+        reversedBody.put("amount", 191);
+        String changed = ReflectionTestUtils.invokeMethod(service, "hash", second);
+        assertThat(changed).isNotEqualTo(original);
+        second.put("customerId", 11L); reversedBody.put("amount", 190);
+        String otherCustomer = ReflectionTestUtils.invokeMethod(service, "hash", second);
+        assertThat(otherCustomer).isNotEqualTo(original);
+    }
+}