Struts2配置错误求解

使用注解配置Struts2后tomcat启动出错，提示如下：（我已经将convention。jar文件放到lib目录下了）
严重: Exception starting filter Struts2
java.lang.NoClassDefFoundError: org/objectweb/asm/ClassVisitor
at org.apache.struts2.convention.PackageBasedActionConfigBuilder.findActions(PackageBasedActionConfigBuilder.java:376)
at org.apache.struts2.convention.PackageBasedActionConfigBuilder.buildActionConfigs(PackageBasedActionConfigBuilder.java:334)
at org.apache.struts2.convention.ClasspathPackageProvider.loadPackages(ClasspathPackageProvider.java:53)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:215)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:380)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:424)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:69)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:295)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:422)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:115)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4071)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4725)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3460)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:426)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1357)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1649)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1658)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1658)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1638)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.ClassNotFoundException: org.objectweb.asm.ClassVisitor
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 22 more