How to avoid Method Overloading in Java to avoid duplicates?

Question

I have 2 method which performs 80% same work but differ in result processing. I am doing :

 private <T> T getResponse(final RestURI query, final Class<T> responseClass) throws IOException {
        T response = null;

        final RestResponse<Record> tempResponse = getResponseFromDataPath(query);

        if (isResponseOK(tempResponse, query)) {
            final CustomReader reader = createCustomReaderFromResponse(tempResponse);
            response = objectMapper.readValue(reader, responseClass);
                                                          ^
            // DIFFERENCE --------------------------------|
        }

        return response;
    }

    private <T> T getResponse(final RestURI query, final TypeReference valueTypeRef) throws IOException {
        T response = null;

        final RestResponse<Record> tempResponse = getResponseFromDataPath(query);

        if (isResponseOK(tempResponse, query)) {
            final CustomReader reader = createCustomReaderFromResponse(tempResponse);
            response = objectMapper.readValue(reader, valueTypeRef);
                                                          ^
            // DIFFERENCE --------------------------------|
        }

        return response;
    }

This looks like lot of duplicate. How do I make this such that I reduce the duplicates.

Pass all three parameters into a single constructor, and the simply pass null in the unused parameter. Check for null to distinguish inside the constructor. — Susmit Agrawal
– Susmit Agrawal, Commented Aug 23, 2018 at 7:38
Honestly, it would be helpful if you somehow marked or explicitly repeated the not common parts. I had to re-read the code 5 times to figure where they are different. — GhostCat
– GhostCat, Commented Aug 23, 2018 at 7:46

ernest_k · Accepted Answer · 2018-08-23 07:41:57Z

5

You can use a BiFunction parameter that calls objectMapper:

private <T> T getResponse(final RestURI query, 
    final BiFunction<CustomReader, ObjectMapper, T> mapper) throws IOException {
    T response = null;

    final RestResponse<Record> tempResponse = getResponseFromDataPath(query);

    if (isResponseOK(tempResponse, query)) {
        final CustomReader reader = createCustomReaderFromResponse(tempResponse);
        response = mapper.apply(reader, objectMapper); 
    }

    return response;
}

And callers can choose how to call objectMapper:

getResponse(query, 
   (reader, objectMapper) -> objectMapper.readValue(reader, <valueTypeRef>);

Or:

getResponse(query, 
    (reader, objectMapper) -> objectMapper.readValue(reader, <class>);

answered Aug 23, 2018 at 7:41

ernest_k

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3 Comments

GhostCat Over a year ago

The important thing to keep in mind: this is only a good idea when that method stays private. Would it be something that external code is using, then obviously do not want to expose such a level of detail. Nice answer though!

ernest_k Over a year ago

@GhostCat Agreed.

davidxxx Over a year ago

As getResponse() is a private method, the caller method can directly reference the objectMapper field in the lambda body : getResponse(query, reader -> objectMapper.readValue(reader, valueTypeRef));. So Function<CustomReader, T> is enough. Which simplifies things in both sides.

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