ClassCastException com.gao5805123.servlet.ServletDemo cannot be cast to javax.servlet.Servlet

异常信息

严重: Allocate exception for servlet servletDemo
java.lang.ClassCastException: com.gao5805123.servlet.ServletDemo cannot be cast to javax.servlet.Servlet
	at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1144)
	at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:865)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:136)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

异常原因

<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>servlet-api</artifactId>
	<version>6.0.29</version>
</dependency>
JVM在检测到两个类型间转换不兼容时引发的运行时异常

解决方法

<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>servlet-api</artifactId>
	<version>6.0.29</version>
	<scope>provided</scope>
</dependency>