How to use regular expressions to identify the error message in the JSON String?

Question

I am working on a project in which I am making a call to one of my servers using RestTemplate which is running a restful service and getting the response back from them.

The response that I will be getting from my server can be either of these error responses (that's all I have for error response) if something has gone wrong -

{"warning": "user_id not found", "user_id": some_user_id}
{"error": "user_id for wrong partition", "user_id": some_user_id, "partition": some_partition}
{"error": "missing client id", "client_id":2000}

or below successful response (it can be any random json string key can also be different) -

{"@data": {"oo":"1205000384","p":"2047935"} 

1. If I am getting any error response as mentioned above, then I am deserializing it (my bad :( ) so that I can log them as an error with a specific error or warning I got front the server which can be for example - user_id not found or missing client id .
2. If it is a successful response then also I am deserializing it which I don't need for my use case as we don't have any POJO and I just need to return the response as it is which I have got from the server.

In my use case, I don't need to deserialize my response string if it is a successful response as we don't have any POJO for that and we are returning the response string as it is which we have got from the server. But just for logging specific error messages (if I am getting error response from the server) I am deserializing it which I am thinking is unnecessary. There might be better solution for my use case.

Below is my Java client which is calling Callable task using future.get -

public class TestingClient implements IClient {

    private ExecutorService service = Executors.newFixedThreadPool(10);
    private RestTemplate restTemplate = new RestTemplate();

    @Override
    public String executeSync(ClientKey keys) {

        String response = null;
        try {

            ClientTask ClientTask = new ClientTask(keys, restTemplate);
            Future<String> future = service.submit(ClientTask);
            response = handle.get(keys.getTimeout(), TimeUnit.MILLISECONDS);
        } catch (TimeoutException e) {

        } catch (Exception e) {

        }

        return response;
    }
}

And now below is my ClientTask class which implements Callable interface. In the call method, I am generating an URL and then hit the server using RestTemplate and get the response back -

class ClientTask implements Callable<String> {

    private ClientKey cKeys;
    private RestTemplate restTemplate;

    public ClientTask(ClientKey cKeys, RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
        this.cKeys = cKeys;
    }

    @Override
    public String call() throws Exception {

        // .. some code here
        String url = "some_url";            
        String response = restTemplate.getForObject(url, String.class);

        String test = checkJSONResponse(response);

        return test;
    }

    private String checkJSONResponse(final String response) throws Exception {

        // may be there are some better way of doing it for my scenario instead of using GSON
        Gson gson = new Gson();
        String str = null;
        JsonObject jsonObject = gson.fromJson(response, JsonObject.class); // parse it, may be performance issues here/
        if (jsonObject.has("error") || jsonObject.has("warning")) {

        final String error = jsonObject.get("error") != null ? jsonObject.get("error").getAsString() : jsonObject
        .get("warning").getAsString();

        // log specific `error` here using log4j
        str = response;
        } else {
            str = response;
        }

        return str;
    }
}

As you can see in my above code we are deserializing the JSON string only to log specific error messages if we are getting any error response back. But for successful response we don't need any deserialization but still we are doing it.

Is there any better way of solving this problem? Because currently I am seeing some performance issues with the GSON deserialization.

The only way I can identify successful response along with error response is with error or warning in the response so I am thinking of using regular expressions which can identify error or warning as the key in the response string. If they contain error or warning in the response string then extract the specific error or warning message and log it.

I guess there might be some better way of solving this problem without paying the cost for deserialization.

Answer 1

Just relying on a regex is I think to dangerous. What if the server slightly changes the output format?

I would try to make a quick test, possibly with a simple regexp looking for the string "error" and if there is a chance that it is an error response do a full deserialization to determine if it really was an error or not.

You would pay the extra cost only for false positives when a regular response by chance triggers the quick check.

Answer 2

我将使用http代码来控制成功/失败数据解析。