public RestTemplateBuilder withSpecificJsonMessageConverter() {
    isUseDefaultJsonMessageConverter = false;

    AbstractHttpMessageConverter<?> jsonMessageConverter = new MappingJackson2HttpMessageConverter(
            Jackson2ObjectMapperBuilder
                    .json()
                    .featuresToEnable(
                            DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY,
                            DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT)
                    .build());
    jsonMessageConverter.setSupportedMediaTypes(Lists.newArrayList(
            MediaType.TEXT_HTML, MediaType.TEXT_PLAIN,
            MediaType.APPLICATION_JSON));

    withMessageConverter(jsonMessageConverter);

    return this;
}
 

private void applyDefaultCharset() {
	for (HttpMessageConverter<?> candidate : this.getMessageConverters()) {
		if (candidate instanceof AbstractHttpMessageConverter) {
			AbstractHttpMessageConverter<?> converter = (AbstractHttpMessageConverter<?>) candidate;
			if (converter.getDefaultCharset() != null) {
				converter.setDefaultCharset(this.charset);
			}
		}
	}
}
 

/**
 * Apply the configured charset as a default to registered part converters.
 */
private void applyDefaultCharset() {
	for (HttpMessageConverter<?> candidate : this.partConverters) {
		if (candidate instanceof AbstractHttpMessageConverter) {
			AbstractHttpMessageConverter<?> converter = (AbstractHttpMessageConverter<?>) candidate;
			// Only override default charset if the converter operates with a charset to begin with...
			if (converter.getDefaultCharset() != null) {
				converter.setDefaultCharset(this.charset);
			}
		}
	}
}
 

private void writeInternal(Object object, HttpOutputMessage outputMessage) throws Exception {
	Method method = AbstractHttpMessageConverter.class.getDeclaredMethod(
			"writeInternal", Object.class, HttpOutputMessage.class);
	method.setAccessible(true);
	method.invoke(this.converter, object, outputMessage);
}