android - 响应代码 304 和 200 时的 Volley 异常错误

Question

在使用 Volley 库时，我注意到在进行 POST 时 JsonObjectRequest , 如果服务器返回代码 304 或 200 而响应中没有数据 (response.data) , Volley 将其解释为错误响应，而不是成功。

我设法通过在方法 Response<JSONObject> parseNetworkResponse(NetworkResponse response) 中添加几行代码来解决它在类里面JsonObjectRequest.java .

@Override
protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
    try {
        if (!response.notModified) {// Added for 304 response
            String jsonString = new String(response.data,
                    HttpHeaderParser.parseCharset(response.headers));
            return Response.success(new JSONObject(jsonString),
                    HttpHeaderParser.parseCacheHeaders(response));
        } else // Added for 304 response
            return Response.success(new JSONObject(),HttpHeaderParser.parseCacheHeaders(response));
    } catch (UnsupportedEncodingException e) {
        Log.v("Volley", "UnsupportedEncodingException " + response.statusCode);
        if (response.statusCode == 200)// Added for 200 response
            return Response.success(new JSONObject(), HttpHeaderParser.parseCacheHeaders(response));
        else
            return Response.error(new ParseError(e));
    } catch (JSONException je) {
        Log.v("Volley", "JSONException " + response.statusCode);
        if (response.statusCode == 200)// Added for 200 response
            return Response.success(new JSONObject(),HttpHeaderParser.parseCacheHeaders(response));
        else
            return Response.error(new ParseError(je));
    }
}

它是这个问题的最佳解决方案吗？

谢谢!

编辑

检查类 BasicNetwork.java我意识到 Volley 通过询问是否 httpResponse.getEntity() != null 来检查响应是否没有数据.

// Some responses such as 204s do not have content. We must check.
    if (httpResponse.getEntity() != null) {
        responseContents = entityToBytes(httpResponse.getEntity());         
    } else {// Add 0 byte response as a way of honestly representing a
    // no-content request.
        responseContents = new byte[0];
    }

但问题仍然是当 Volley 尝试使用 response.data == new byte[0] 创建新字符串时出现的 JSONException在 parseNetworkResponse 方法中。

Answer 1

Miguel- 是否仅当响应成功时才调用此方法？

对于所有状态代码 <200 或状态代码 >200 的 volley 调用 parseNetworkError(VolleyError volleyError) 而不是 parseNetworkResponse(NetworkResponse response) 方法。看这里-

https://android.googlesource.com/platform/frameworks/volley/+/master/src/com/android/volley/toolbox/BasicNetwork.java

行号-118-120

  if (statusCode < 200 || statusCode > 299) {
                throw new IOException();
   }

和对应的catch block 行号——128 -151

catch (IOException e) {
            int statusCode = 0;
            NetworkResponse networkResponse = null;
            if (httpResponse != null) {
                statusCode = httpResponse.getStatusLine().getStatusCode();
            } else {
                throw new NoConnectionError(e);
            }
            VolleyLog.e("Unexpected response code %d for %s", statusCode, request.getUrl());
            if (responseContents != null) {
                networkResponse = new NetworkResponse(statusCode, responseContents,
                        responseHeaders, false);
                if (statusCode == HttpStatus.SC_UNAUTHORIZED ||
                        statusCode == HttpStatus.SC_FORBIDDEN) {
                    attemptRetryOnException("auth",
                            request, new AuthFailureError(networkResponse));
                } else {
                    // TODO: Only throw ServerError for 5xx status codes.
                    throw new ServerError(networkResponse);
                }
            } else {
                throw new NetworkError(networkResponse);
            }
        }

如果您想覆盖此行为，您可以在 BasicNetwork.java->performRequest 方法中添加您的状态代码特定实现。

编辑:所以这不是因为状态代码，而是因为空响应。好吧，我认为您正在做正确的事情来实现您的自定义 Request 类。Volley 带有一些预定义的流行请求类型以便于使用，但您始终可以创建自己的请求。我宁愿在反序列化之前简单地检查以下字符串是否为空，而不是基于状态代码的实现 -

String jsonString = new String(response.data,
                HttpHeaderParser.parseCharset(response.headers));
if (!jsonString .isEmpty()) {
                 return Response.success(new JSONObject(jsonString),
                HttpHeaderParser.parseCacheHeaders(response));
}
else {
return Response.success(new JSONObject(),
                    HttpHeaderParser.parseCacheHeaders(response));
}

**还没有测试过这个，但你明白了:)