数据库中有好多字段是null，如果强行转换为toString会抛出异常。dto的Date类型，可以在返回json的时候，直接为null，或者日期？

project-order/src/main/java/com/alibaba/cloud/integration/order/dto/WorkbenchEngineersGanttRespDTO.java

@@ -2,6 +2,7 @@ package com.alibaba.cloud.integration.order.dto;
 
 import lombok.experimental.Accessors;
 
+import java.util.Date;
 import java.util.List;
 
 @lombok.Data
@@ -46,7 +47,7 @@ public class WorkbenchEngineersGanttRespDTO {
         /**
          * 结束时间
          */
-        private String endTime;
+        private Date endTime;
         /**
          * 服务单ID
          */
@@ -58,7 +59,7 @@ public class WorkbenchEngineersGanttRespDTO {
         /**
          * 开始时间
          */
-        private String startTime;
+        private Date startTime;
         private List<?> tips;
     }
 

project-order/src/main/java/com/alibaba/cloud/integration/order/service/impl/WorkbenchServiceImpl.java

@@ -82,7 +82,7 @@ public class WorkbenchServiceImpl implements WorkbenchService {
                 mapEngineers.put(entity.getEngineerCode(), new ArrayList<>());
             }
             WorkbenchEngineersGanttRespDTO.Timeline timeline = new WorkbenchEngineersGanttRespDTO.Timeline();
-            timeline.setStartTime(entity.getStartTime().toString()).setEndTime(entity.getEndTime().toString())
+            timeline.setStartTime(entity.getStartTime()).setEndTime(entity.getEndTime())
                     .setServiceOrderId(entity.getOrderId()).setServiceOrderStatus(entity.getStatus());
             timeline.setTips(getOrderTips(entity.getOrderId()));
         }