in log4j2-ecs-layout/src/main/java/co/elastic/logging/log4j2/EcsLayout.java [272:289]
private static void addJson(StringBuilder buffer, StringBuilder jsonBuffer) {
if (isObject(jsonBuffer)) {
moveToRoot(jsonBuffer);
buffer.append(jsonBuffer);
buffer.append(", ");
} else {
buffer.append("\"message\":");
if (isString(jsonBuffer)) {
buffer.append(jsonBuffer);
} else {
// message always has to be a string to avoid mapping conflicts
buffer.append('"');
JsonUtils.quoteAsString(jsonBuffer, buffer);
buffer.append('"');
}
buffer.append(", ");
}
}