Q: How does SuperMap iServer get a sublayer style of a map？

A: Send the http request through the rest API, and the request example is as follows: 
http://supermapiserver:8090/iserver/services/map-world/rest/maps/WorldMap/layers/Capitals@World@@ WorldMap/style.rjson 
Please refer to the Help document > REST API > services > root > maps > map > layers > layer > style. You can view the detailed request methods and parameters.