My ear is not able to find ejb module classes

I am new to the EAR. I have developed a web module and a ejb module which are dependent on each other for the functionality. For that I am trying to confiure them in a EAR. I mapped both web and ejb module to EAR and can see application.xml as

  <display-name>EBS-ear</display-name>
  <module>
    <ejb>EBS-ejb.jar</ejb>
  </module>
  <module>
    <web>
      <web-uri>EBS-web.war</web-uri>
      <context-root>EBS-web</context-root>
    </web>
  </module>
</application>

But when I try to execute EAR my server throws below exception

23:58:29,606 ERROR [io.undertow.request] (default task-5) UT005023: Exception handling request to /EBS-web/: java.lang.NoClassDefFoundError: com/ebs/service/UserAuthorisationService
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)
    at java.lang.Class.getConstructor0(Unknown Source)
    at java.lang.Class.getConstructor(Unknown Source)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyAction(XmlConfigurationProvider.java:480)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:429)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:556)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:295)
    at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:264)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
    at org.apache.struts2.dispatcher.Dispatcher.getContainer(Dispatcher.java:967)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:435)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:479)
    at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)
    at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:111)
    at org.wildfly.extension.undertow.security.RunAsLifecycleInterceptor.init(RunAsLifecycleInterceptor.java:84)
    at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:97)
    at io.undertow.servlet.core.ManagedFilter.createFilter(ManagedFilter.java:80)
    at io.undertow.servlet.core.ManagedFilter.getFilter(ManagedFilter.java:66)
    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
    at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84)
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
    at io.undertow.jsp.JspFileHandler.handleRequest(JspFileHandler.java:32)
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
    at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
    at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
    at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
    at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:805)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: com.ebs.service.UserAuthorisationService from [Module "deployment.EBS-web.war:main" from Service Module Loader]
    at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:198)
    at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:363)
    at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:351)
    at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:93)
    ... 61 more

What I can understand from above is the EAR is not able to locate the classes present in the EJB module and therefore throwing the exception. I am using WildFLy 10 server and eclipse IDE.

An EAR file is just a container for various enterprise modules (EJB jars, WAR files and regular jar files) with some well defined (but often misunderstood) rules for which classes can see which.

In most cases, you will see an EAR file with the following internal structure:

EAR
 \-lib
 |  \- utilityA.jar
 |  \- utilityB.jar
 |  \- ...
 |- ejb-jarC.jar
 |- ejb-jarD.jar
 |- ...
 |- warE.jar
 |- warF.jar
 |- ...

For the purposes of class visibility, this EAR above shows five modules:

lib module
ejb-jar1.jar
ejb-jar2.jar
war1.jar
war2.jar

where:

All jars in the lib module are considered to be in the same module;
All jars and classes in each WAR file are considered to be in the same module;
Each ejb-jar is an independent module.

Typically, each module has it's own class loader.

Now, JBossAS/WildFly relaxes the class visibility rules a little to make developers lives simpler (and for historical reasons). On these server implementations the rules are:

Each WAR module can see it's own classes, the classes in each EJB jar and the classes in every jar in the the EAR/lib directory
- it cannot see the classes in other WAR modules;
Each EJB module can see it's own classes, the classes in other EJB modules and the classes in every jar in the the EAR/lib directory;
- it cannot see the classes in any WAR modules;
The classes in the EAR/lib module can only see each other:
- they cannot see classes in any EJB modules or WAR modules

A stricter implementation would require the definition of manifest Class-path entries in order to make EJB modules visible to each other and WAR modules.

Now, given all of the above your particular problem is most likely one of:

a class in the lib module attempting to access a class in one of the EJB modules or one of the WAR modules - did you place the struts2 jars in the EAR/lib directory?
a class in an EJB module trying to access a class in one of the WAR modules

Having said all of that you could make your life a lot easier since you're using a JavaEE 7 server. Just package everything including EJBs into a WAR file. Chances are you are gaining no benefit from building and deploying an EAR