从OKHttp拦截器返回错误(使用改造)

Question

我正在使用OkHttp和Retrofit来制作我的应用程序的网络请求.我还使用拦截器进行身份验证,并在必要时重试请求.

服务器有时会出现临时问题,并返回空体,尽管响应状态为200 OK.这会导致我的应用程序崩溃,因为调用了Retrofit Callback的成功块,返回(并使用GSON解析)的自定义对象为null,成功回调中的代码假定返回一个对象.

我已经向服务器团队报告了这个问题,但我也想修复它,而不必使用null检查将所有成功回调代码包装在应用程序上.

Currenty我倾向于两个选项,虽然任何其他想法都是最受欢迎的:1)不从拦截器返回(这甚至可能吗？)并且只显示一个错误对话框2)返回一些会使Retrofit调用失败的部分打回来.

我的代码如下.正如您所看到的,当收到空体时,我会重试该请求最多3次.

@Override
public Response intercept(Chain chain) throws IOException
{
    // First
    Request request = chain.request();
    Response response = chain.proceed(request);

    ....
    ....
    ....

    // Retry empty body response requests for a maximum of 3 times
    Integer retryMaxCount = 3;
    MediaType contentType = response.body().contentType();
    String bodyString = response.body().string();

    while (bodyString.length() == 0 && retryMaxCount > 0)
    {
        //Empty body received!, Retrying...

        retryMaxCount--;
        response = chain.proceed(request);
        bodyString = response.body().string();
    }

    if (bodyString.length() != 0)
    {
        // Create and return new response because it was consumed
        ResponseBody newResponseBody = ResponseBody.create(contentType, bodyString);
        return response.newBuilder().body(newResponseBody).build();
    }
    else
    {
        // WHAT TO WRITE HERE???
    }
}

非常感谢.

Answer 1

刚刚遇到了相同的情况，这篇文章帮助我实施了解决方案。感谢@mastov 指出正确的方向。

使用后端 api，即使出现错误也始终返回 HTTP 200。这是我的错误响应示例

{"status":403,"message":"Bad User credentials","time":1495597740061,"version":"1.0"}

这是一个简单的实现来补充这个答案。

public Response intercept(Chain chain) throws IOException {
        Request request   = chain.request();
        Response response = chain.proceed(request);
        ResponseBody body = response.body();
        // Only intercept JSON type responses and ignore the rest.
        if (body != null && body.contentType() != null && body.contentType().subtype() != null && body.contentType().subtype().toLowerCase().equals("json")) {
            String errorMessage = "";
            int errorCode       = 200; // Assume default OK
            try {
                BufferedSource source = body.source();
                source.request(Long.MAX_VALUE); // Buffer the entire body.
                Buffer buffer   = source.buffer();
                Charset charset = body.contentType().charset(Charset.forName("UTF-8"));
                // Clone the existing buffer is they can only read once so we still want to pass the original one to the chain.
                String json     = buffer.clone().readString(charset);
                JsonElement obj = new JsonParser().parse(json);
                // Capture error code an message.
                if (obj instanceof JsonObject && ((JsonObject) obj).has("status")) {
                    errorCode   = ((JsonObject) obj).get("status").getAsInt();
                }
                if (obj instanceof JsonObject && ((JsonObject) obj).has("message")) {
                    errorMessage= ((JsonObject) obj).get("message").getAsString();
                }
            } catch (Exception e) {
                Log.e(TAG, "Error: " + e.getMessage());
            }
            // Check if status has an error code then throw and exception so retrofit can trigger the onFailure callback method.
            // Anything above 400 is treated as a server error.
            if(errorCode > 399){
                throw new Exception("Server error code: " + errorCode + " with error message: " + errorMessage);
            }
        }

        return response;
    }