com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input

Question

I need to map a JSON array object with java POJO class. I wrote the code like this:

// execute the client with get method 
InputStream inputStream = getMethod.getResponseBodyAsStream();

BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

ObjectMapper objectMapper = new ObjectMapper();

JsonFactory jsonFactory = new JsonFactory();
List<OwnerDetail> owners = new ArrayList<>();
JsonParser jsonParser = jsonFactory.createJsonParser(inputStream);

if (jsonParser.nextToken() != null && jsonParser.)
{ // end-of-input
  owners = objectMapper.readValue(bufferedReader, TypeFactory.defaultInstance().constructCollectionType(List.class, OwnerDetail.class));
}

The above block is giving me following error:

com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: java.io.BufferedReader@5e66c5fc; line: 1, column: 1]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:164)
at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3029)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2971)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2128)

Any help would be appreciated. Thanks.

Answer 1

After reading response the data from the response is consumed. If your code is in interceptor you could try creating response again and return as below:

    Request request = chain.request();
    Response originalResponse = chain.proceed(request);
    final ResponseBody original = originalResponse.body();
    // if(request.url().toString().equalsIgnoreCase(string)){
    if (originalResponse.code() == HttpURLConnection.HTTP_OK) {
        try {
            String response = originalResponse.body().string();
            JSONObject mainObject = new JSONObject(response);

            // your mapping - manipulation code here.
            originalResponse = originalResponse.newBuilder()
                            .header("Cache-Control", "max-age=60")
                            .body(ResponseBody.create(original.contentType(),
                                    mainObject.toString().getBytes()))
                            .build();

        } catch (JSONException | IOException e) {
            e.printStackTrace();
        }
    }
    return originalResponse;

Here response is created again and returned.

Do let me know any update.

Answer 2

The use of both inputStream and bufferedReader seems wrong. If you've made a JsonParser for the input, it is probably best to continue using it for the object mapping. There might be a problem with the buffered reader eagerly reading all the content from the stream, leaving nothing for the JSON parser to read.

There also looks to be a section missing from your code, in the if condition.

Something like this:

    if (parser.isExpectedStartArrayToken()) {
        owners = mapper.readValue(parser, mapper.getTypeFactory().constructCollectionType(List.class, OwnerDetail.class));
    }

Extra notes:

• It's recommended not to wrap streams in buffering/decoding (InputStreamReader) before passing to Jackson as Jackson's parsers have heavily optimised this process already
  • Actually, wrapping InputStreamReader in BufferedReader is practically always redundant as InputStreamReader does buffer content
• TypeFactory and JsonFactory can both be obtained from an ObjectMapper instance
• No need to initialise owners to an empty list that will get overridden anyway-- declare it without initialisation and use an else to set the default only when necessary