[英]How to read a JSON response using HttpClient in vb.net
我已經建立了一個用於訪問WEB API服務的Java例程,但是我在ASP.Net的VB等效版本中苦苦掙扎。 我得到了API響應,但是我不知道如何將其轉換為json元素。
Java版本是:
public boolean canLogin(){
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(hostURL + TOKEN_ACCESS_URL);
httppost.addHeader("Accept", "application/json");
// Add the post content
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(3);
nameValuePairs.add(new BasicNameValuePair("grant_type", "password"));
nameValuePairs.add(new BasicNameValuePair("username", accessUserName));
nameValuePairs.add(new BasicNameValuePair("password", accessPassword));
try {
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
} catch (UnsupportedEncodingException e1) {
mobileLogDataHandler.ToLog(LogType.Error, "UnsupportedEncodingException closing data stream with error: " + e1.getLocalizedMessage() + ",detail:" + e1.getMessage() + " in canLogin", mResolver, RemoteDataHandler.class);
return false;
}
// post the server
InputStream inputStream = null;
String result = null;
try {
HttpResponse response = httpclient.execute(httppost);
if (response.getStatusLine().getStatusCode()!=200){
mobileLogDataHandler.ToLog(LogType.Error, "Failed to get server token with error: " + response.getStatusLine().toString() + " in canLogin", mResolver, this.getClass());
return false;
}
HttpEntity entity = response.getEntity();
inputStream = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);// json is UTF-8 by default
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line + "\n");
}
result = sb.toString();
inputStream.close();
} catch (ClientProtocolException e) {
mobileLogDataHandler.ToLog(LogType.Error, "ClientProtocolException trying to get bearer token from server with error: " + e.getLocalizedMessage() + ",detail:" + e.getMessage() + " in canLogin", mResolver, this.getClass());
return false;
} catch (IOException e) {
mobileLogDataHandler.ToLog(LogType.Error, "IOException trying to get bearer token from server with error: " + e.getLocalizedMessage() + ",detail:" + e.getMessage() + " in canLogin", mResolver, this.getClass());
return false;
}
//read the response content
try{
JSONObject jObject = new JSONObject(result);
bearerToken = jObject.getString("access_token");
String expiryIntervalInSeconds = jObject.getString("expires_in");
return canSaveNewBearerToken(bearerToken, expiryIntervalInSeconds);
} catch (JSONException e){
mobileLogDataHandler.ToLog(LogType.Error, "JSON error reading data sent from server for bearer token request with error: " + e.getLocalizedMessage() + ",detail:" + e.getMessage() + " in canLogin", mResolver, this.getClass());
return false;
}
但是在我的VB版本中-這就是我所擁有的。 我如何閱讀它,以便從其中獲取json對象:
Public Function canLogin() As Boolean
Dim client As HttpClient = New HttpClient
client.DefaultRequestHeaders.Accept.Add(
New System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"))
'Dim content As HttpContent = New StringContent("grant_type=password&username=" & mAccessUserName & "&password=" & mAccessPassword)
Dim urlEncodedList As New List(Of KeyValuePair(Of String, String))
urlEncodedList.Add(New KeyValuePair(Of String, String)("grant_type", "password"))
urlEncodedList.Add(New KeyValuePair(Of String, String)("username", mAccessUserName))
urlEncodedList.Add(New KeyValuePair(Of String, String)("password", mAccessPassword))
Dim content As New FormUrlEncodedContent(urlEncodedList)
'content.Headers.ContentType = New Headers.MediaTypeHeaderValue("application/x-www-form-urlencoded") 'not sure if i need this
Dim response As HttpResponseMessage = client.PostAsync(New Uri(mHostURL & TOKEN_ACCESS_URL), content).Result
If response.IsSuccessStatusCode Then
Return True
Else
Return False
End If
End Function
任何幫助表示贊賞。
Dim response As HttpResponseMessage = client.PostAsync(
New Uri("someuri"), content).Result
If response.IsSuccessStatusCode Then
Dim json As String = response.Content.ReadAsStringAsync().Result
Dim bearerToken As String = DirectCast(
JObject.Parse(json).SelectToken("access_token"),
String)
Return True
Else
Return False
End If
PS。 確保您有對JSON.NET的引用。 另外,在ASP.NET中使用.Result
也是一個問題,很容易導致死鎖。 最好使用await
。
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