You can invoke a Sling Servlet deployed within Adobe Experience Manager by using Java APIs located in the org.apache.commons.httpclient.HttpClient package. This Java package contains classes that let you perform HTTP operations such as invoking a Servlet's doGet method. For information about this Java package, see Package org.apache.commons.httpclient.
Assume that you have a business requirement to invoke a deployed AEM Sling Servlet from another AEM service defined within an OSGi bundle. You can perform this use case by using a org.apache.commons.httpclient.HttpClient object.
To read this development article, click: https://helpx.adobe.com/experience-manager/using/HttpClient_AEM.html.