java - 如何在 Java Android Spring 中接收验证错误

Question

我在 Android (Java) 中使用 Spring 向后端 API 发送 API 请求。我的问题是如何在 ex 400 错误请求响应中将验证错误接收到错误处理程序。这是我的代码:

 class RestTask extends AsyncTask<String,Void,ResponseEntity<ExpectedReturn>>
    {
        protected ResponseEntity<ExpectedReturn> doInBackground(String... uri)
        {
            try{
                final String url = uri[0];
                RestTemplate restTemplate = new RestTemplate();
                restTemplate.setErrorHandler(subscriber.getErrorHandler());
                restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
                // set authentication tokens:
                ResponseEntity<ExpectedReturn> response = restTemplate.exchange(url,callMethod,httpEntity, expectedReturnClass);
                return response;
            }catch(Exception e)
            {
                System.out.println(e.getMessage());
            }
            return null;
        }

        @Override
        protected void onPostExecute(ResponseEntity<ExpectedReturn> result) {
            if(result !=null && result.getBody() !=null)
            {
                subscriber.getSubscriber().onComplete(result.getBody(),result.getStatusCode());
            }
        }
    }

我的问题是，如果 post 数据验证失败(不正确)，API 将作为带有错误的 JSON 错误对象返回，例如:

如果出现验证错误，将调用错误处理程序，并使用 ClientHttpResponse 对象作为参数。调用 response.getBody() 返回一个 InputStream。我的问题是，是否有任何方法可以接收从 JSON 错误响应(如上所示)映射到错误处理程序的对象，或者可能将输入流转换为可读的内容(如 HashMap )，以便我可以显示返回的错误API(例如:“需要名称”等...)？

Answer 1

我已经测试了您的代码，如果出现 400 次错误请求，catch block 会收到一个 HttpClientErrorException 实例，该实例具有将错误主体获取为字符串的方法:

private class HttpRequestTask extends AsyncTask<Void, Void, String> {
    @Override
    protected String doInBackground(Void... params) {
        try {
            final String url = "https://reqres.in/api/login";
            RestTemplate restTemplate = new RestTemplate();
            //Same result with restTemplate.exchange() too
            return restTemplate.postForObject(url, "{\n" +
                    "    \"email\": \"peter@klaven\"\n" +
                    "}", String.class);

        } catch (Exception e) {
            Log.e(TAG, e.getMessage());
            if (e instanceof HttpClientErrorException) {
                String responseBodyAsString = ((HttpClientErrorException) e).getResponseBodyAsString();
                Log.e(TAG, "Validation error" + responseBodyAsString);
                //You can parse this with gson or jackson here
                return responseBodyAsString;
            }
        }

        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        Log.d(TAG, "onPostExecute() called with: result = [" + result + "]");
    }

}

打印在:

W/RestTemplate: POST request for "https://reqres.in/api/login" resulted in 
400 (Bad Request); invoking error handler
E/MainActivity: 400 Bad Request
E/MainActivity: Validation error{"error":"Missing email or username"}
D/MainActivity: onPostExecute() called with: result = [{"error":"Missing email or username"}]

如果您想使用无默认错误处理程序并设置您的自定义错误处理程序，您可以通过这种方式将错误消息作为字符串获取:

restTemplate.setErrorHandler(new ResponseErrorHandler() {
                @Override
                public boolean hasError(ClientHttpResponse response) throws IOException {
                    return response.getStatusCode().is4xxClientError();
                }

                @Override
                public void handleError(ClientHttpResponse response) throws IOException {
                    String errorResponse = new String(getResponseBody(response), getCharset(response).name());
                    Log.e(TAG, "handleError: called with: " + errorResponse);
                }
            });

private byte[] getResponseBody(ClientHttpResponse response) {
    try {
        InputStream responseBody = response.getBody();
        if (responseBody != null) {
            return FileCopyUtils.copyToByteArray(responseBody);
        }
    } catch (IOException ex) {
        // ignore
    }
    return new byte[0];
}

private Charset getCharset(ClientHttpResponse response) {
    HttpHeaders headers = response.getHeaders();
    MediaType contentType = headers.getContentType();
    return contentType != null ? contentType.getCharSet() : Charset.defaultCharset();
}

然后您可以使用 Jackson 或 Gson 来解析错误响应，如下所示:

new Gson().fromJson(responseBodyAsString, ExpectedResponse.class);

请注意，我刚刚做了与 DefaultResponseErrorHandler

中实现的相同的事情

编辑:整个 AsyncTask 和 Spring Android API 都太过时了，下面是 Retrofit 的同一个例子:

        api.login(new BodyModel("peter@klaven"))
            .enqueue(new Callback<ExpectedModel>() {
                @Override
                public void onResponse(@NonNull Call<ExpectedModel> call, @NonNull Response<ExpectedModel> response) {
                    if (response.isSuccessful()) {
                        //Do what you got to do
                    } else {
                        Converter<ResponseBody, ErrorModel> converter = MainActivity.this.retrofit.responseBodyConverter(ErrorModel.class, new Annotation[0]);
                        ErrorModel errorModel = null;
                        try {
                            errorModel = converter.convert(response.errorBody());
                            Toast.makeText(MainActivity.this, errorModel.toString(), Toast.LENGTH_SHORT).show();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }

                }

                @Override
                public void onFailure(@NonNull Call<ExpectedModel> call, @NonNull Throwable t) {
                    t.printStackTrace();
                }
            })

您可以找到完整的 gist in my github repo