调用Dropbox API获取文件列表时遇404错误求助

首次接触Dropbox API，编写代码尝试获取文件列表时遇到错误：Access dropbox file - The remote server returned an error: (404) Not Found。修改安全协议类型后仍出现相同错误，代码如下：

Dim token As String
token = "sl.B6........."
Dim _command As String
_command = "https://api.dropboxapi.com/2/files/list_folder"
Dim Request As HttpWebRequest
Request = HttpWebRequest.Create(_command)
Request.Method = "GET"
Request.KeepAlive = True
Request.ContentType = "application/x-www-form-urlencoded"
Request.UserAgent = "Mozilla/5.0 (Windows NT 6.3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36"
Request.AllowAutoRedirect = True
Request.Headers.Add("Authorization", "Bearer " & token)
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
Dim Response As HttpWebResponse = Request.GetResponse()

解决方法 #

• 核心错误：请求方法不匹配
  Dropbox的/2/files/list_folder接口仅支持POST请求，你代码中使用的GET方法会直接触发404错误，这和安全协议无关。
• 具体修正点：
  1. 将请求方法改为POST：Request.Method = "POST"
  2. 接口要求JSON格式的请求体（即使查询根目录，也需要传入{"path": ""}），需添加请求内容
  3. 把ContentType改为application/json，匹配接口的请求格式要求

修正后的完整代码示例：

Dim token As String
token = "sl.B6........."
Dim _command As String
_command = "https://api.dropboxapi.com/2/files/list_folder"
Dim Request As HttpWebRequest = CType(HttpWebRequest.Create(_command), HttpWebRequest)
Request.Method = "POST"
Request.KeepAlive = True
Request.ContentType = "application/json"
Request.UserAgent = "Mozilla/5.0 (Windows NT 6.3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36"
Request.AllowAutoRedirect = True
Request.Headers.Add("Authorization", "Bearer " & token)
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

' 添加JSON请求体
Dim postData As String = "{""path"": """"}"
Dim byteArray As Byte() = System.Text.Encoding.UTF8.GetBytes(postData)
Request.ContentLength = byteArray.Length
Using dataStream As Stream = Request.GetRequestStream()
    dataStream.Write(byteArray, 0, byteArray.Length)
End Using

' 读取响应内容
Using Response As HttpWebResponse = CType(Request.GetResponse(), HttpWebResponse)
    Using reader As New StreamReader(Response.GetResponseStream())
        Dim responseText As String = reader.ReadToEnd()
        ' 此处可处理响应内容，比如输出或解析
        Console.WriteLine(responseText)
    End Using
End Using

内容的提问来源于stack exchange，提问作者Luca Geremei