Can we get the site.com site url dynamically in class or vf page in Salesforce?

Try this code hope this will help you also:-

String name = 'mysite';

Site site = [
SELECT GuestUserId
FROM Site
WHERE Name = :name
];

String path = '/sites/servlet.SiteDebugMode';
PageReference pr = new PageReference(path);
pr.getParameters().put('guid', site.GuestUserId);
pr.getParameters().put('sitedebugmode', 'x');
String url = pr.getContent().toString().substringAfter('URL=').substringBefore(path);

System.debug(url); //eg "http://dev-bigass.cs81.force.com/mysite"

Hi,

Try this -

String sitename = 'testSiteName';

Site site = [SELECT GuestUserId FROM Site WHERE Name = :sitename ];

String sitepath = '/sites/servlet.SiteDebugMode';
PageReference prRef = new PageReference(sitepath );
prRef .getParameters().put('guid', site.GuestUserId);
prRef .getParameters().put('sitedebugmode', 'x');
String siteurl = prRef .getContent().toString().substringAfter('URL=').substringBefore(sitepath );

System.debug(siteurl ); //eg "http://dev-bigass.cs81.force.com/testSiteName"

Hope this helps.