GWT错误

假如启动GWT时出现如下错误:

    java.lang.NoSuchMethodError: org.mortbay.thread.Timeout.<init>(Ljava/lang/Object;)V
	at org.mortbay.io.nio.SelectorManager$SelectSet.<init>(SelectorManager.java:306)
	at org.mortbay.io.nio.SelectorManager.doStart(SelectorManager.java:223)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
	at org.mortbay.jetty.nio.SelectChannelConnector.doStart(SelectChannelConnector.java:303)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
	at org.mortbay.jetty.Server.doStart(Server.java:233)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
	at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:542)
	at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:431)
	at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1053)
	at com.google.gwt.junit.JUnitShell.getUnitTestShell(JUnitShell.java:680)
	at com.google.gwt.junit.JUnitShell.runTest(JUnitShell.java:625)
	at com.google.gwt.junit.client.GWTTestCase.runTest(GWTTestCase.java:456)
	at junit.framework.TestCase.runBare(TestCase.java:134)
	at junit.framework.TestResult$1.protect(TestResult.java:110)
	at junit.framework.TestResult.runProtected(TestResult.java:128)
	at junit.framework.TestResult.run(TestResult.java:113)
	at junit.framework.TestCase.run(TestCase.java:124)
	at com.google.gwt.junit.client.GWTTestCase.run(GWTTestCase.java:311)
	at junit.framework.TestSuite.runTest(TestSuite.java:232)
	at junit.framework.TestSuite.run(TestSuite.java:227)
	at org.junit.internal.runners.OldTestClassRunner.run(OldTestClassRunner.java:76)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:38)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

   则可能是GWT的包与AppEngine的包放反了，需要将GWT的包放在AppEngine包的前面,杯催~~