protected String readJsonFrom(final InputStream json) throws IOException {
        return isJsonFormat() && isLenient()
            ? readHumanJson(IOUtils.toString(json, StandardCharsets.UTF_8))
            : String.join("\n", IOUtils.readLines(json, StandardCharsets.UTF_8));
    }
Gets object mapper and builds on if uninitialized.

@return the object mapper
core/cas-server-core-util-api/src/main/java/org/apereo/cas/util/serialization/BaseJacksonSerializer.java