!MESSAGE Could not publish to the server.

When I start my server & try publishing it  I got the following error.When I opened the application.xml of MDM(inside META-INF),it says an unexpected error occurred.



!MESSAGE Could not publish to the server.
!STACK 0
java.lang.NullPointerException
    at org.eclipse.emf.ecore.resource.impl.ResourceSetImpl.getResource(Unknown Source)
    at org.eclipse.jem.internal.util.emf.workbench.ProjectResourceSetImpl.getResource(Unknown Source)
    at org.eclipse.wst.common.internal.emfworkbench.WorkbenchResourceHelper.getOrCreateResource(Unknown Source)
    at org.eclipse.wst.common.internal.emfworkbench.integration.EditModel.getResource(Unknown Source)
    at org.eclipse.wst.common.componentcore.internal.ArtifactEditModel.getResource(Unknown Source)
    at org.eclipse.jst.j2ee.componentcore.util.EARArtifactEdit.getDeploymentDescriptorResource(Unknown Source)
    at org.eclipse.jst.j2ee.componentcore.EnterpriseArtifactEdit.getDeploymentDescriptorRoot(Unknown Source)
    at org.eclipse.jst.j2ee.componentcore.util.EARArtifactEdit.getApplication(Unknown Source)
    at org.eclipse.jst.j2ee.internal.deployables.J2EEFlexProjDeployable.isNestedJ2EEModule(Unknown Source)
    at org.eclipse.jst.j2ee.internal.deployables.J2EEFlexProjDeployable.shouldIncludeUtilityComponent(Unknown Source)
    at org.eclipse.wst.web.internal.deployables.ComponentDeployable.addUtilMembers(Unknown Source)
    at org.eclipse.jst.j2ee.internal.deployables.J2EEFlexProjDeployable.members(Unknown Source)
    at org.eclipse.wst.server.core.internal.ModulePublishInfo.fillCache(Unknown Source)
    at org.eclipse.wst.server.core.internal.ModulePublishInfo.getDelta(Unknown Source)
    at org.eclipse.wst.server.core.internal.ServerPublishInfo.getDelta(Unknown Source)
    at org.eclipse.wst.server.core.internal.Server.getPublishedResourceDelta(Unknown Source)
    at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.getPublishedResourceDelta(Unknown Source)
    at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(Unknown Source)
    at org.eclipse.wst.server.core.internal.Server.doPublish(Unknown Source)
    at org.eclipse.wst.server.core.internal.Server.publish(Unknown Source)
    at org.eclipse.wst.server.core.internal.PublishServerJob.run(Unknown Source)
    at org.eclipse.core.internal.jobs.Worker.run(Unknown Source)

Solution:
I dont know the exact reason for the error but the simple solution is to close & reopen the workspace :)