We can also add solrcore.properties in the configuration directory to specify user-defined properties that can be set in solrconfig.xml. 

For example, solr.autoCommit.maxTime can be added to solrcore.properties.

On the use of APIs, the Solr core will have its core.properties automatically created. In the case of the SolrCloud collection, we can submit our own parameters, which will go into the respective core.properties. The only thing to make sure is prefixing the parameter name with property as a URL parameter:

http://localhost:8983/solr/admin/collections?action=CREATE&name=gettingstarted&numShards=1&property.user.name=Dharmesh Vasoya

 This will create core.properties with the following entry:

user.name=Dharmesh Vasoya

Now this property can be used in solrconfig.xml as ${user.name}.