Maven 加载 Servlet API 两次

Question

我收到 org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter 的 ClassCastException

在日志中我看到我的 javax.servlet.Filter 被加载了两次。

一次来自我的本地 maven 存储库

[Loaded javax.servlet.Filter from file:/C:/Users/xxxx/.m2/repository/javax/servlet/servlet-api/2.5/servlet-api-2.5.jar]

，另一个来自 tomcat

[Loaded javax.servlet.Filter from file:/C:/Apache.org/apache-tomcat-6.0.32/lib/servlet-api.jar]

一旦加载第二个版本的过滤器，我就会在服务器日志中收到以下异常。

Apr 20, 2011 2:42:21 PM org.apache.catalina.core.StandardContext filterStart
SEVERE: Exception starting filter struts2
java.lang.ClassCastException:    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter cannot be cast to javax.servlet.Filter
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:275)
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.ContainerBase.addChildInternal(ContainerBase.java:799)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:779)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:601)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:675)
at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:601)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:502)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1315)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:324)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:142)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1061)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
at org.apache.catalina.core.StandardService.start(StandardService.java:525)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Apr 20, 2011 2:42:21 PM org.apache.catalina.core.StandardContext start
SEVERE: Error filterStart

这是我的 pom.xml 的片段，

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>2.5</version>
    <type>jar</type>
    <scope>provided</scope>
    <optional>false</optional>
</dependency>

感谢您的查看。

Answer 1

您应该在 pom.xml 中将 servlet-api 依赖项标记为 provided 这样 Maven 就不会将其包含在最终构建中。然后执行mvn clean package

Answer 2

尝试从 Tomcat 临时目录中清除所有爆炸的战争。有时，这些垃圾会导致加载一个类的多个版本。特别是如果您在此期间更改了 pom.xml。执行此操作并将范围保留为提供的