Question

我正在使用OkHttp和Retrofit来制作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，虽然响应状态为200 OK，但返回空体。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，但是我也希望修复它，而不必使用null检查将所有成功回调代码包装在整个应用程序中。

当前我倾向于两种选择，尽管欢迎任何其他想法： 1）不从拦截器返回（这是否可能？）并且只显示错误对话框 2）返回会使Retrofit调用失败的部分回调。

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

刚刚有相同的情况，这篇文章帮助我实施了解决方案。感谢@mastov指出了正确的方向。

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，以补充这个答案。

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;
    }

Answer 2

返回自定义响应将解决此问题。将此代码段放入拦截器中，然后再返回

    if(response.body() == null)
          return new Response.Builder()
                    .code(404)
                    .body(response.body())
                    .protocol(Protocol.HTTP_2)
                    .message("Token has expired please login once again")
                    .request(chain.request())
                    .build()

Answer 3

你应该抛出 IOException。在这种情况下，retrofit2 将使用 onFailure 路径。

Answer 4

我的解决方案来自okhttp3.logging.HttpLoggingInterceptor

class ErrorResponseInterceptor : Interceptor {

    override fun intercept(chain: Interceptor.Chain): Response {
        val response = chain.proceed(chain.request())
        val code = response.code()
        if (code in 400..500) {
            responseBody(response)?.also { errorString ->
                // error string here is a body of server error
            }
        }
        return response
    }

    private fun responseBody(response: Response): String? {
        val responseBody = response.body() ?: return null
        val contentLength = responseBody.contentLength()

        if (contentLength == 0L) {
            return null
        }

        val source = responseBody.source()
        source.request(Long.MAX_VALUE) // Buffer the entire body.
        var buffer = source.buffer()
        val headers = response.headers()

        if ("gzip".equals(headers.get("Content-Encoding"), ignoreCase = true)) {
            var gzippedResponseBody: GzipSource? = null
            try {
                gzippedResponseBody = GzipSource(buffer.clone())
                buffer = okio.Buffer()
                buffer.writeAll(gzippedResponseBody)
            } finally {
                gzippedResponseBody?.close()
            }
        }

        val charset: Charset = responseBody.contentType()?.charset(UTF8) ?: UTF8
        return buffer.clone().readString(charset)
    }

    private companion object {
        val UTF8: Charset = Charset.forName("UTF-8")
    }
}

从OKHttp拦截器返回错误（使用改造）

4 个答案: