Spring Boot REST映射冲突事件在不同的控制器中(Spring Boot REST mapping conflict event in different controller)

 问题出在你的比较中。 命令Document.getElementById返回DBNull ，它本身不等于Null。 因此，当您执行： 
 
if ($ie.Document.getElementById("admin"))
{
   ...
}
 
 你总是和True回来。 正如您在以下示例中所看到的， $my_element不等于$null ，其类型为DBNull 。 
 
PS > $my_element = $ie.Document.getElementById("admin")

PS > $my_element -eq $null
False

PS > $my_element.GetType()

IsPublic IsSerial Name                                     BaseType                                                                                                     
-------- -------- ----                                     --------   
True     True     DBNull                                   System.Object   
 
 我建议你使用其中一个比较来确定“admin”是否确实存在： 
 
PS > $my_element.ToString() -eq ""
True

PS > [String]::IsNullOrEmpty($my_element.ToString())
True

PS > $my_element.ToString() -eq [String]::Empty
True
 
 如果比较返回True则表示该值为Empty，因此“admin”不存在。 当然，您可以使用-ne以获得更多便利。 

The problem is in your comparison. The command Document.getElementById is returning with DBNull which by itself doesn't equals to Null. Therefore, when you execute:
 
if ($ie.Document.getElementById("admin"))
{
   ...
}
 
You'd always returned with True. As you can see in the following example, $my_element isn't equals to $null and its type is DBNull.
 
PS > $my_element = $ie.Document.getElementById("admin")

PS > $my_element -eq $null
False

PS > $my_element.GetType()

IsPublic IsSerial Name                                     BaseType                                                                                                     
-------- -------- ----                                     --------   
True     True     DBNull                                   System.Object   
 
I'd suggest you to use one of this comparisons to determine if "admin" really exists:
 
PS > $my_element.ToString() -eq ""
True

PS > [String]::IsNullOrEmpty($my_element.ToString())
True

PS > $my_element.ToString() -eq [String]::Empty
True
 
If the comparisons return with True it means that the value is Empty so "admin" is not exists. Of course you can use -ne for more convenience.