解决：问题4：平板设备绑定问题：在PAD设备管理把PAD设备关联WL0023账号修改成WL01000003， 再进入客户端账号对WL0023进行修改， 发现关联的PAD设备信息还存在，并且点确定提示“该平板设备不存在”

src/main/java/com/om/controller/admin/DeviceController.java

@@ -88,6 +88,16 @@ public class DeviceController {
     @PostMapping("update")
     @Transactional
     public Result update(@RequestBody Device device) {
+        //根据id查询旧数据
+        Device byId = deviceService.getById(device.getId());
+        if (!byId.getUsername().equals(device.getUsername())) {
+            LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
+            queryWrapper.eq(User::getUsername, byId.getUsername());
+            User user = userMapper.selectOne(queryWrapper);
+            user.setDeviceSn("");
+            user.setUpdateTime(LocalDateTime.now());
+            userMapper.updateById(user);
+        }
         if (StringUtils.isNotBlank(device.getUsername())) {
             LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
             queryWrapper.eq(User::getUsername, device.getUsername());