的try/catch不是在PowerShell中

Question

工作，我具备的功能GET_USER，搜索键入的用户名：

function get_user 
{ 
    $url2 = "myurl/userName:" + $userName 

    $contentType2 = "application/json" 
    $basicAuth2 = post_token 
    $headers2 = @{ 
       Authorization = $basicAuth2 
      } 
    $body2 = @{ 
       grant_type = 'client_credentials' 
      } 
    $getUser = Invoke-RestMethod -Method Get -Uri $url2 -ContentType $contentType2 -Headers $headers2 -Body $body2 

    return $getUser.userName 
} 

然后，我有我的主要方法try/catch语句这是不工作：

#MAIN 

try { 

$userName = Read-Host -Prompt "Input the user's username" 
$getUser = get_user 

    if ($userName -eq $getUser) 
     { 
      $courseId = Read-Host -Prompt "Input the course's ID" 
      $availability = Read-Host -Prompt "Available? (Yes/No)" 
      $courseRoleId = Read-Host -Prompt "Course Role? (Student/Instructor)" 

      $confirmationEnrollment = putStudentCourse 
      " " 
      "####################################################" 
      "Success!" 
      "####################################################" 
     }  
    else 
     { 
      $firstName = Read-Host -Prompt "First Name" 
      $lastName = Read-Host -Prompt "Last Name" 
      $netId = $userName 
      $email = $userName + "@school.edu" 
      $password = Read-Host -Prompt "Password" 
      $uin = Read-Host -Prompt "ID Number" 
      $isAvailable = Read-Host -Prompt "Available? (Yes/No)" 

      $confirmationUserCreate = user_create 
      " " 
      "####################################################" 
      "User created!" 
      "####################################################" 
      " " 
      $courseId = Read-Host -Prompt "Input the course's ID" 

      $confirmEnroll = putStudentCourse 
      " " 
      "####################################################" 
      "User enrolled!" 
      "####################################################" 
     } 
    } 
catch [System.Net.HttpWebRequest] 
    { 
     "####################################################" 
     "User not found. We'll create it now!" 
     "####################################################" 
     " " 
    } 

现在你键入一个不存在的用户名后抛出错误：

Invoke-RestMethod : The remote server returned an error: (404) Not Found. 
At E:\Blackboard_REST_API_Project\PowerShell\Post_Student_Course.ps1:42 char:13 
+  $getUser = Invoke-RestMethod -Method Get -Uri $url2 -ContentType $contentType2 ... 
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
    + CategoryInfo   : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException 
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand 

我想隐藏红色错误并输出我在catch语句中的内容，但它跳过catch并直接跳到else找不到用户名。有任何想法吗？

Answer 1

关于Try Catch最可能的原因是发生了Catch之后明确列出的错误以外的错误。测试这种方法是删除指定的异常类型，并捕获所有错误。我不建议在生产代码中这样做，但为了测试它至少会揭示您的总体想法是否正确。然后，您可以澄清要捕捉的具体错误。

对于理想的行为似乎存在一些混淆。基于问题下面的评论和你的代码评论，你似乎在说如果请求抛出一个错误，那么用户一定不存在，应该创建。如果这是正确的，那么要小心，因为这种假设并不总是如此。

一旦错误被抛出，你实际上会跳过你的If Else结构中的所有代码。基本上我认为你想在你的ELSE语句中使用逻辑并将其移入Catch块。如果你想尝试创建用户，或者如果get_user抛出一个错误，或者如果它不抛出一个错误，但If条件失败，那么你会想要在catch和else中的相​​同逻辑。当然，创建一个函数可以更好地调用而不是重复代码。

本质：

Try{ 
    #try to invoke the request 

    #if the request did not fail then compare the user entered text to the text returned from the request 
    #if these match then user already exists 
    #else the user does not exist so create it here 
} 
catch{ 
    #if the request failed assume that the user does not exist and create it here 

} 

Answer 2

你检查错误的异常类型的catch语句来。一个404引发错误的WebException：

$Error[0] 
Invoke-RestMethod : The remote server returned an error: (404) Not Found. 
At line:2 char:5 
+  Invoke-RestMethod -Uri "http://www.vg.no/nonexistingpage" 
+  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
    + CategoryInfo   : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException 
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand 

$Error[0].Exception 

The remote server returned an error: (404) Not Found. 

$Error[0].Exception.GetType().FullName 

System.Net.WebException 

尝试：

try { 
    Invoke-RestMethod -Uri "http://www.vg.no/nonexistingpage" 
} 
catch [System.Net.WebException] 
{ 
    "Exception caught!" 
} 

至于剧本，我可能会做这样的事情，使创建用户，如果它不（404-错误）：

#MAIN 

$userName = Read-Host -Prompt "Input the user's username" 

try { 
    $getUser = get_user 
} catch [System.Net.WebException] { 
    #User doesn't exist, create new 
    $firstName = Read-Host -Prompt "First Name" 
    $lastName = Read-Host -Prompt "Last Name" 
    $netId = $userName 
    $email = $userName + "@school.edu" 
    $password = Read-Host -Prompt "Password" 
    $uin = Read-Host -Prompt "ID Number" 
    #Is it required to create user? If not, remove as it's specified later 
    $isAvailable = Read-Host -Prompt "Available? (Yes/No)" 

    $confirmationUserCreate = user_create 
    " " 
    "####################################################" 
    "User created!" 
    "####################################################" 

    #Verify user was created 
    $getUser = get_user 
} 

#Not sure if test is still needed.. 
if($userName -eq $getUser) { 
    $courseId = Read-Host -Prompt "Input the course's ID" 
    $availability = Read-Host -Prompt "Available? (Yes/No)" 
    $courseRoleId = Read-Host -Prompt "Course Role? (Student/Instructor)" 

    $confirmationEnrollment = putStudentCourse 
    " " 
    "####################################################" 
    "Success!" 
    "####################################################" 
} 

提示：您应该在函数中使用参数，而不要依赖可能存在的变量。