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问题:
I am using Google Volley on the Android platform. I am having a problem in which the error parameter in onErrorResponse is returning a null networkResponse For the RESTful API I am using, I need to determine the Http Status Code which is often arriving as 401 (SC_UNAUTHORIZED) or 500 (SC_INTERNAL_SERVER_ERROR), and I can occasionally check via:
final int httpStatusCode = error.networkResponse.statusCode; if(networkResponse == HttpStatus.SC_UNAUTHORIZED) { // Http status code 401: Unauthorized. }
This throws a NullPointerException because networkResponse is null.
How can I determine the Http Status Code in the function onErrorResponse?
Or, how can I ensure error.networkResponse is non-null in onErrorResponse?
回答1:
Or, how can I ensure error.networkResponse is non-null in onErrorResponse?
My first thought would be to check if the object is null.
@Override public void onErrorResponse(VolleyError error) { NetworkResponse networkResponse = error.networkResponse; if (networkResponse != null && networkResponse.statusCode == HttpStatus.SC_UNAUTHORIZED) { // HTTP Status Code: 401 Unauthorized } }
Alternatively, you could also try grabbing the Status Code by extending the Request class and overriding parseNetworkResponse.
For example, if extending the abstract Request<T> class
public class GsonRequest<T> extends Request<T> { ... private int mStatusCode; public int getStatusCode() { return mStatusCode; } ... @Override protected Response<T> parseNetworkResponse(NetworkResponse response) { mStatusCode = response.statusCode; try { Log.d(TAG, "[raw json]: " + (new String(response.data))); Gson gson = new Gson(); String json = new String(response.data, HttpHeaderParser.parseCharset(response.headers)); return Response.success(gson.fromJson(json, mClazz), HttpHeaderParser.parseCacheHeaders(response)); } catch (UnsupportedEncodingException e) { return Response.error(new ParseError(e)); } catch (JsonSyntaxException e) { return Response.error(new ParseError(e)); } } ... }
Or, if you are using one of the toolbox classes that already extend the abstract Request<T> class and you don't want to muddle up the implementation for parseNetworkResponse(NetworkResponse networkResponse), continue overriding the method but return the super's implementation via super.parseNetworkResponse(networkResponse)
e.g. StringResponse
public class MyStringRequest extends StringRequest { private int mStatusCode; public MyStringRequest(int method, String url, Listener<String> listener, ErrorListener errorListener) { super(method, url, listener, errorListener); } public int getStatusCode() { return mStatusCode; } @Override protected Response<String> parseNetworkResponse(NetworkResponse response) { mStatusCode = response.statusCode; return super.parseNetworkResponse(response); } }
usage:
public class myClazz extends FragmentActivity { private Request mMyRequest; ... public void makeNetworkCall() { mMyRequest = new MyNetworkRequest( Method.GET, BASE_URL + Endpoint.USER, new Listener<String>() { @Override public void onResponse(String response) { // Success } }, new ErrorListener() { @Override public void onErrorResponse(VolleyError error) { if (mMyRequest.getStatusCode() == 401) { // HTTP Status Code: 401 Unauthorized } } }); MyVolley.getRequestQueue().add(request); }
Of course, the option to override the method inline is available too
public class MyClazz extends FragmentActivity { private int mStatusCode; ... public void makeNetworkCall() { StringRequest request = new StringRequest( Method.GET, BASE_URL + Endpoint.USER, new Listener<String>() { @Override public void onResponse(String response) { // Success } }, new ErrorListener() { @Override public void onErrorResponse(VolleyError error) { if (mStatusCode == 401) { // HTTP Status Code: 401 Unauthorized } } }) { @Override protected Response<String> parseNetworkResponse(NetworkResponse response) { mStatusCode = response.statusCode; return super.parseNetworkResponse(response); } }; MyVolley.getRequestQueue.add(request); }
Update:
HttpStatus is Deprecated. Use HttpURLConnection instead. See Link.
回答2:
401 Not Supported by Volley
It turns out that it is impossible to guarantee that error.networkResponse is non-null without modifying Google Volley code because of a bug in Volley that throws the Exception NoConnectionError for Http Status Code 401 (HttpStatus.SC_UNAUTHORIZED) in BasicNetwork.java (134) prior to setting the value of networkResponse.
Work-Around
Instead of fixing the Volley code, our solution in this case was to modify the Web Service API to send Http Error Code 403 (HttpStatus.SC_FORBIDDEN) for the particular case in question.
For this Http Status Code, the value of error.networkResponse is non-null in the Volley error handler: public void onErrorResponse(VolleyError error). And, error.networkResponse.httpStatusCode correctly returns HttpStatus.SC_FORBIDDEN.
Other-Suggestions
Rperryng's suggestion of extending the Request<T> class may have provided a solution, and is a creative and excellent idea. Thank you very much for the detailed example. I found the optimal solution for our case is to use the work-around because we are fortunate enough to have control of the web services API.
I might opt for fixing the Volley code in one location within BasicNetwork.java if I did not have access to making a simple change at the server.
回答3:
Volley supports HTTP 401 Unauthorized response. But this response MUST include "WWW-Authenticate" header field.
Without this header, 401 response causes "com.android.volley.NoConnectionError: java.io.IOException: No authentication challenges found" error.
For more detail : https://stackoverflow.com/a/25556453/860189
If you consume 3rd party API's and have no right to change response header, you may consider to implement your own HttpStack because of this exception thrown from HurlStack. Or better, use OkHttpStack as a HttpStack.
回答4:
The error.networkResponse will be null, if the device has no network connection (you can proof this by enabling the airplane mode). Look at the corresponding code fragment from the Volley library.
You have to check then, if the error is an instance of the NoConnectionError, before you look for the networkResponse. I cannot agree, that 401 error is not supported by Volley, I tested it and got a non-null networkResponse object back with 401 status code. Look at the corresponding code here.
回答5:
Network response can be received in the following format
NetworkResponse response = error.networkResponse; if(response != null && response.data != null){ switch(response.statusCode){ case 403: json = new String(response.data); json = trimMessage(json, "error"); if(json != null) displayMessage(json); break; } }
回答6:
This is how I check and grep error.
// TimeoutError => most likely server is down or network is down. Log.e(TAG, "TimeoutError: " + (e instanceof TimeoutError)); Log.e(TAG, "NoConnectionError: " + (e instanceof NoConnectionError)); /*if(error.getCause() instanceof UnknownHostException || error.getCause() instanceof EOFException ) { errorMsg = resources.getString(R.string.net_error_connect_network); } else { if(error.getCause().toString().contains("Network is unreachable")) { errorMsg = resources.getString(R.string.net_error_no_network); } else { errorMsg = resources.getString(R.string.net_error_connect_network); } }*/ Log.e(TAG, "NetworkError: " + (e instanceof NetworkError)); Log.e(TAG, "AuthFailureError: " + (e instanceof AuthFailureError)); Log.e(TAG, "ServerError: " + (e instanceof ServerError)); //error.networkResponse.statusCode // inform dev Log.e(TAG, "ParseError: " + (e instanceof ParseError)); //error.getCause() instanceof JsonSyntaxException Log.e(TAG, "NullPointerException: " + (e.getCause() instanceof NullPointerException)); if (e.networkResponse != null) { // 401 => login again Log.e(TAG, String.valueOf(e.networkResponse.statusCode)); if (e.networkResponse.data != null) { // most likely JSONString Log.e(TAG, new String(e.networkResponse.data, StandardCharsets.UTF_8)); Toast.makeText(getApplicationContext(), new String(e.networkResponse.data, StandardCharsets.UTF_8), Toast.LENGTH_LONG).show(); } } else if (e.getMessage() == null) { Log.e(TAG, "e.getMessage"); Log.e(TAG, "" + e.getMessage()); if (e.getMessage() != null && e.getMessage() != "") Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show(); else Toast.makeText(getApplicationContext(), "could not reach server", Toast.LENGTH_LONG).show(); } else if (e.getCause() != null) { Log.e(TAG, "e.getCause"); Log.e(TAG, "" + e.getCause().getMessage()); if (e.getCause().getMessage() != null && e.getCause().getMessage() != "") Toast.makeText(getApplicationContext(), e.getCause().getMessage(), Toast.LENGTH_LONG).show(); else Toast.makeText(getApplicationContext(), "could not reach server", Toast.LENGTH_LONG).show(); }
回答7:
I handle this problem manually:
Download Volley library from github and add into AndroidStudio project
Go to com.android.volley.toolbox.HurlStack class
Find setConnectionParametersForRequest(connection, request); line inside of performRequest method
And finally add this codes belew of setConnectionParametersForRequest(connection, request); line :
// for avoiding this exception : No authentication challenges found try { connection.getResponseCode(); } catch (IOException e) { e.printStackTrace(); }
