Using Tomcat 9 and Oracle DB i got the following errors when I was trying to execute XWiki for the first time:
Root Cause
com.xpn.xwiki.XWikiException: Error number 11007 in 0: Failed to extract Entity Resource Reference from URL [http://localhost:8080/xwiki/bin/view/Main/]
com.xpn.xwiki.XWiki.initializeResourceFromURL(XWiki.java:1046)
com.xpn.xwiki.XWiki.getXWiki(XWiki.java:906)
com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:345)
com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:250)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:112)
org.xwiki.wysiwyg.filter.ConversionFilter.doFilter(ConversionFilter.java:109)
org.xwiki.container.servlet.filters.internal.SetHTTPHeaderFilter.doFilter(SetHTTPHeaderFilter.java:63)
org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:208)
org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:111)
org.xwiki.resource.servlet.RoutingFilter.doFilter(RoutingFilter.java:132)
Root Cause
java.lang.RuntimeException: Failed to locate wiki descriptor for alias [localhost]
org.xwiki.url.internal.standard.AbstractWikiReferenceExtractor.getWikiDescriptorByAlias(AbstractWikiReferenceExtractor.java:80)
org.xwiki.url.internal.standard.DomainWikiReferenceExtractor.resolveDomainBasedWikiReference(DomainWikiReferenceExtractor.java:61)
org.xwiki.url.internal.standard.DomainWikiReferenceExtractor.extract(DomainWikiReferenceExtractor.java:47)
org.xwiki.url.internal.standard.entity.BinEntityResourceReferenceResolver.extractWikiReference(BinEntityResourceReferenceResolver.java:51)
org.xwiki.url.internal.standard.entity.AbstractEntityResourceReferenceResolver.resolve(AbstractEntityResourceReferenceResolver.java:87)
org.xwiki.url.internal.standard.entity.AbstractEntityResourceReferenceResolver.resolve(AbstractEntityResourceReferenceResolver.java:50)
org.xwiki.url.internal.GenericResourceReferenceResolver.resolve(GenericResourceReferenceResolver.java:61)
org.xwiki.url.internal.GenericResourceReferenceResolver.resolve(GenericResourceReferenceResolver.java:47)
org.xwiki.url.internal.standard.StandardExtendedURLResourceReferenceResolver.resolve(StandardExtendedURLResourceReferenceResolver.java:65)
org.xwiki.url.internal.standard.StandardExtendedURLResourceReferenceResolver.resolve(StandardExtendedURLResourceReferenceResolver.java:43)
org.xwiki.url.internal.DefaultResourceReferenceResolver.resolve(DefaultResourceReferenceResolver.java:93)
org.xwiki.url.internal.DefaultResourceReferenceResolver.resolve(DefaultResourceReferenceResolver.java:48)
com.xpn.xwiki.XWiki.initializeResourceFromURL(XWiki.java:1041)
com.xpn.xwiki.XWiki.getXWiki(XWiki.java:906)
com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:345)
com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:250)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:112)
org.xwiki.wysiwyg.filter.ConversionFilter.doFilter(ConversionFilter.java:109)
org.xwiki.container.servlet.filters.internal.SetHTTPHeaderFilter.doFilter(SetHTTPHeaderFilter.java:63)
org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:208)
org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:111)
org.xwiki.resource.servlet.RoutingFilter.doFilter(RoutingFilter.java:132)