I want to create service user using YAML Config & Access to get Resource Resolver.

Hi @ashok67621, you will need to follow below 3 steps.

1. Create yaml (using AC Tool) file definition to create system user and assign it to group (I have used administrator group as an example - but you can use any other group)
   

   - user_config:
   
        - custom-system-user:
          - isMemberOf: administrators
            path: /home/users/system/custom
            isSystemUser: true

2. Add an entry in the Apache Sling Service User Mapper Service (it can be done manually from OSGi console, or via xml/config file) - below example shows config file usage.
   Name of the file: org.apache.sling.serviceusermapping.impl.ServiceUserMapperImpl.amended-custom.config
   

   service.ranking=I"0"
   user.mapping=["<bundle-symbolic-name>:<name-of-service>\=custom-system-user"]

3. Get resource resolver instance that will use above user
   

   @Reference
   private ResourceResolverFactory resolverFactory;
   
   Map<String, Object> param = new HashMap<String, Object>();
   param.put(ResourceResolverFactory.SUBSERVICE, "name-of-service");
   
   ResourceResolver resourceResolver = resourceResolverFactory.getServiceResourceResolver(param);