GSON: How to get a case insensitive element from Json?

Question

Code shown below works well when JSON object contains jsonKey as it was passed to the method. I wonder ... if there is a way to get a value assigned to a case insensitive representation of a key?

Example:

public String getOutputEventDescription(JsonElement outputEvent) throws ParserException {
    return retrieveString(outputEvent, DESCRIPTION);
}

Should work regardless whether DESCRIPTION is defined as "Description", "description" or "DeScRipTIOn"

protected String retrieveString(JsonElement e, String jsonKey) throws ParserException {

JsonElement value = e.getAsJsonObject().get(jsonKey);

if (value == null) {
    throw new ParserException("Key not found: " + jsonKey);
}

if (value.getAsString().trim().isEmpty()) {
    throw new ParserException("Key is empty: " + jsonKey);
}

return e.getAsJsonObject().get(jsonKey).getAsString();
}

Answer 1

I faced the similar issue. I did this to get around the issue. (Replaced all the keys with their corresponding lowercase version and had all lower case fields in matching class). Hope this helps.

 input = input.replaceAll("\\s","");
        Matcher m = Pattern.compile("\"\\b\\w{1,}\\b\"\\s*:").matcher(input);
        StringBuilder sanitizedJSON = new StringBuilder();
        int last = 0;
        while (m.find()) {
            sanitizedJSON.append(input.substring(last, m.start()));
            sanitizedJSON.append(m.group(0).toLowerCase());
            last = m.end();
        }
        sanitizedJSON.append(input.substring(last));

        input = sanitizedJSON.toString();

Answer 2

I stumbled across this question when I ran into an issue where a different naming convention was being used at the two endpoints and subsequently discovered a less invasive solution.

Gson does support setting a naming convention that is used when mapping from the Java model names to the JSON names, both when when serializing and deserializing. Use the setFieldNamingPolicy method of the builder to change this behavior.

GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE);
Gson gson = gsonBuilder.create();

See here for a nice article on the subject, including an overview of the different policies.

This isn't really a case insensitive solution, but it does provide a way to work around many of the situations where the case is not matching up.