If we don't specify a zkplus in a pom.xml with zkspring-core, the error below will happen:

SEVERE: Unable to load a listenr, [null:jar:file:/Users/hawk/.m2/repository/org/zkoss/zk/zkspring-core/3.1.1/zkspring-core-3.1.1.jar!/metainfo/zk/config.xml:23:12]
org.zkoss.zk.ui.UiException: jar:file:/User...ar!/metainfo/zk/config.xml:23:12: Unable to load org.zkoss.spring.init.CoreWebAppInit
at org.zkoss.zk.ui.sys.ConfigParser.parseClass(ConfigParser.java:744)
at org.zkoss.zk.ui.sys.ConfigParser.parseListener(ConfigParser.java:253)
at org.zkoss.zk.ui.sys.ConfigParser.parseListeners(ConfigParser.java:248)
at org.zkoss.zk.ui.sys.ConfigParser.parseConfigXml(ConfigParser.java:188)
at org.zkoss.zk.ui.http.WebManager.<init>(WebManager.java:132)
at org.zkoss.zk.ui.http.HttpSessionListener23.contextInitialized(HttpSessionListener23.java:140)
at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:549)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:136)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1282)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:518)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:499)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
at org.mortbay.jetty.Server.doStart(Server.java:224)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at runjettyrun.Bootstrap.main(Bootstrap.java:97)
Caused by: java.lang.NoClassDefFoundError: org/zkoss/spring/DelegatingVariableResolver
at org.zkoss.spring.init.CoreWebAppInit.<clinit>(CoreWebAppInit.java:35)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at org.zkoss.lang.Classes.forNameByThread(Classes.java:268)
at org.zkoss.zk.ui.sys.ConfigParser.parseClass(ConfigParser.java:729)
... 15 more
Caused by: java.lang.ClassNotFoundException: org.zkoss.spring.DelegatingVariableResolver
at runjettyrun.ProjectClassLoader.loadClass(ProjectClassLoader.java:91)
... 20 more

The spring's pom.xml should be specified to depend on zkplus.

Benefits

• avoid user frustration and human errors.
• simplify dependency configuration http://books.zkoss.org/wiki/ZK_Spring_Essentials/Getting_Started_with_ZK_Spring/Setting_Up_ZK_Spring_using_Maven