Custome or Dynamic Datasource for jasper Reports

Dear jasper master ,

I am new to jasper

In our organization we calling jasper server from another server by making call from java

url ="https://jasper.ourorganization.com/jasperserver/flow.html?_flowId=viewRe..."+encodeURIComponent(repName)+"&decorate=no&j_username=emr_"+userName+"&j_password=emr_"+passWord+"&viewAsDashboardFrame=false ";

here we are passing

url for jasper server and user name and password.

like that can i pass data source name or Db name and

Main problem is we have so many users more than 300 Clints  and having diff DB s based on the user we need to give Data source so i want pass db name and host name from the above url and based on that user custom data source should give that data .

please help me  to create custom data sources using url parameters or how to store url parameters in jasper server

Thanks

Rajasekhar