org.apache.sling.engine.impl.SlingRequestProcessorImpl service: Uncaught Throwable java.lang.LinkageError: loader constraint violation - AEM

Sometimes we may receive the following exception while invoking the Adobe Experience Manager(AEM) services.

20.12.2014 11:15:31.816 *ERROR* [0:0:0:0:0:0:0:1 [1419054331815] GET /services/EmailServlet HTTP/1.1] org.apache.sling.engine.impl.SlingRequestProcessorImpl service: Uncaught Throwable java.lang.LinkageError: loader consaint violation: when resolving interface method "com..commerce.connector.CommerceService.getSession(Ljavax/servlet/http/HttpServleequest;Ljavax/servlet/http/HttpServleesponse;)Lcom//commerce/connector/session/CommerceSession;" the class loader (instance of org/apache/felix/framework/BundleWiringImpl$BundleClassLoaderJava5) of the current class, com///servlet/EmailServlet, and the class loader (instance of org/apache/felix/framework/BundleWiringImpl$BundleClassLoaderJava5) for resolved class, com//commerce/connector/CommerceService, have different Class objects for the type connector.CommerceService.getSession(Ljavax/servlet/http/HttpServleequest;Ljavax/servlet/http/HttpServleesponse;)Lcom//commerce/connector/session/CommerceSession; used in the signature
at com...servlet.EmailServlet.doPost(EmailServlet.java:67)
at com...servlet.EmailServlet.doGet(EmailServlet.java:56)
at org.apache.sling.api.servlets.SlingSafeMethodsServlet.mayService(SlingSafeMethodsServlet.java:268)
at org.apache.sling.api.servlets.SlingAllMethodsServlet.mayService(SlingAllMethodsServlet.java:139)

This error will be thrown while invoking the service of one bundle from another bundle.

To fix this issue, make sure the required packages from the target bundle is imported to the source bundle.