jetty启动时错误如下,显示servlet类找不到?
2016-03-22 21:04:50.227:WARN:oejuc.AbstractLifeCycle:FAILED o.e.j.w.WebAppContext{/,file:/F:/Project/FireGoBacker/Client/webapp/},F:\Project\FireGoBacker\Client\webapp: java.lang.NoClassDefFoundError: javax/servlet/Servlet
java.lang.NoClassDefFoundError: javax/servlet/Servlet
at java.lang.ClassLoader.findBootstrapClass(Native Method)
at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1012)
at java.lang.ClassLoader.loadClass(ClassLoader.java:413)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.eclipse.jetty.util.Loader.loadClass(Loader.java:100)
at org.eclipse.jetty.util.Loader.loadClass(Loader.java:79)
at org.eclipse.jetty.webapp.WebDescriptor.newParser(WebDescriptor.java:91)
at org.eclipse.jetty.webapp.WebDescriptor.ensureParser(WebDescriptor.java:61)
at org.eclipse.jetty.webapp.Descriptor.parse(Descriptor.java:59)
at org.eclipse.jetty.webapp.WebDescriptor.parse(WebDescriptor.java:148)
at org.eclipse.jetty.webapp.MetaData.setDefaults(MetaData.java:149)
at org.eclipse.jetty.webapp.WebXmlConfiguration.preConfigure(WebXmlConfiguration.java:54)
at org.eclipse.jetty.webapp.WebAppContext.preConfigure(WebAppContext.java:457)
at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:493)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:95)
at org.eclipse.jetty.server.Server.doStart(Server.java:282)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
at net.sourceforge.eclipsejetty.starter.embedded.JettyEmbeddedAdapter.start(JettyEmbeddedAdapter.java:67)
at net.sourceforge.eclipsejetty.starter.common.AbstractJettyLauncherMain.launch(AbstractJettyLauncherMain.java:84)
at net.sourceforge.eclipsejetty.starter.embedded.JettyEmbeddedLauncherMain.main(JettyEmbeddedLauncherMain.java:42)
2016-03-22 21:04:50.231:WARN:oejuc.AbstractLifeCycle:FAILED org.eclipse.jetty.server.Server@246ae04d: java.lang.NoClassDefFoundError: javax/servlet/Servlet
java.lang.NoClassDefFoundError: javax/servlet/Servlet
at java.lang.ClassLoader.findBootstrapClass(Native Method)
at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1012)
at java.lang.ClassLoader.loadClass(ClassLoader.java:413)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.eclipse.jetty.util.Loader.loadClass(Loader.java:100)
at org.eclipse.jetty.util.Loader.loadClass(Loader.java:79)
at org.eclipse.jetty.webapp.WebDescriptor.newParser(WebDescriptor.java:91)
at org.eclipse.jetty.webapp.WebDescriptor.ensureParser(WebDescriptor.java:61)
at org.eclipse.jetty.webapp.Descriptor.parse(Descriptor.java:59)
at org.eclipse.jetty.webapp.WebDescriptor.parse(WebDescriptor.java:148)
at org.eclipse.jetty.webapp.MetaData.setDefaults(MetaData.java:149)
at org.eclipse.jetty.webapp.WebXmlConfiguration.preConfigure(WebXmlConfiguration.java:54)
at org.eclipse.jetty.webapp.WebAppContext.preConfigure(WebAppContext.java:457)
at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:493)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:95)
at org.eclipse.jetty.server.Server.doStart(Server.java:282)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
at net.sourceforge.eclipsejetty.starter.embedded.JettyEmbeddedAdapter.start(JettyEmbeddedAdapter.java:67)
at net.sourceforge.eclipsejetty.starter.common.AbstractJettyLauncherMain.launch(AbstractJettyLauncherMain.java:84)
at net.sourceforge.eclipsejetty.starter.embedded.JettyEmbeddedLauncherMain.main(JettyEmbeddedLauncherMain.java:42)
Exception in thread "main" java.lang.NoClassDefFoundError: javax/servlet/Servlet
at java.lang.ClassLoader.findBootstrapClass(Native Method)
at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1012)
at java.lang.ClassLoader.loadClass(ClassLoader.java:413)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.eclipse.jetty.util.Loader.loadClass(Loader.java:100)
at org.eclipse.jetty.util.Loader.loadClass(Loader.java:79)
at org.eclipse.jetty.webapp.WebDescriptor.newParser(WebDescriptor.java:91)
at org.eclipse.jetty.webapp.WebDescriptor.ensureParser(WebDescriptor.java:61)
at org.eclipse.jetty.webapp.Descriptor.parse(Descriptor.java:59)
at org.eclipse.jetty.webapp.WebDescriptor.parse(WebDescriptor.java:148)
at org.eclipse.jetty.webapp.MetaData.setDefaults(MetaData.java:149)
at org.eclipse.jetty.webapp.WebXmlConfiguration.preConfigure(WebXmlConfiguration.java:54)
at org.eclipse.jetty.webapp.WebAppContext.preConfigure(WebAppContext.java:457)
at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:493)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:95)
at org.eclipse.jetty.server.Server.doStart(Server.java:282)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
at net.sourceforge.eclipsejetty.starter.embedded.JettyEmbeddedAdapter.start(JettyEmbeddedAdapter.java:67)
at net.sourceforge.eclipsejetty.starter.common.AbstractJettyLauncherMain.launch(AbstractJettyLauncherMain.java:84)
at net.sourceforge.eclipsejetty.starter.embedded.JettyEmbeddedLauncherMain.main(JettyEmbeddedLauncherMain.java:42)
可是我明明在项目中都用过了啊,jetty启动时也加载了啊,为什么会有这样的错误?