@Override
    public Object convertRequest(
            ServiceRequestContext ctx, AggregatedHttpRequest request, Class<?> expectedResultType,
            @Nullable ParameterizedType expectedParameterizedResultType) throws Exception {

        if (expectedResultType == String.class ||
            expectedResultType == CharSequence.class) {
            final Charset charset;
            final MediaType contentType = request.contentType();
            if (contentType != null) {
                charset = contentType.charset(ArmeriaHttpUtil.HTTP_DEFAULT_CONTENT_CHARSET);
            } else {
                charset = ArmeriaHttpUtil.HTTP_DEFAULT_CONTENT_CHARSET;
            }
            return request.content(charset);
        }
        return RequestConverterFunction.fallthrough();
    }
Converts the specified {@link AggregatedHttpRequest} to a {@link String}.
core/src/main/java/com/linecorp/armeria/server/annotation/StringRequestConverterFunction.java