JSON parser read an entry by entry from large JSON file

It looks like Gson has a streaming API, which is what you want: https://sites.google.com/site/gson/streaming

With Jackson you can use a SAX-like approach (streaming) using a JsonParser object, in your case it would be something like this:

JsonFactory jsonFactory = new JsonFactory();
JsonParser parser = jsonFactory.createParser(new File("/path/to/my/jsonFile"));

// Map where to store your field-value pairs per object
Map<String, String> fields = new HashMap<String, String>();

JsonToken token;
while ((token = parser.nextToken()) != JsonToken.END_ARRAY) {
    switch (token) {

        // Starts a new object, clear the map
        case START_OBJECT:
            fields.clear();
            break;

        // For each field-value pair, store it in the map 'fields'
        case FIELD_NAME:
            String field = parser.getCurrentName();
            token = parser.nextToken();
            String value = parser.getValueAsString();
            fields.put(field, value);
            break;

        // Do something with the field-value pairs
        case END_OBJECT:
            doSomethingWithTheObject(fields)
            break;
        }
    }
    parser.close();