Spring boot内嵌的tomcat启动失败

根据这篇guide创建了一个简单的spring boot应用，能运行且成功的访问。但移植到现有项目（基于hbase）中的时候，却报出以下错误：

SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[]]
	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.util.concurrent.FutureTask.get(FutureTask.java:188)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:801)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
	... 6 more
Caused by: java.lang.NoSuchMethodError: javax.servlet.ServletContext.addServlet(Ljava/lang/String;Ljavax/servlet/Servlet;)Ljavax/servlet/ServletRegistration$Dynamic;
	at org.springframework.boot.context.embedded.ServletRegistrationBean.onStartup(ServletRegistrationBean.java:156)
	at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext$1.onStartup(EmbeddedWebApplicationContext.java:219)
	at org.springframework.boot.context.embedded.tomcat.ServletContextInitializerLifecycleListener.lifecycleEvent(ServletContextInitializerLifecycleListener.java:54)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5343)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more

一般碰到NoSuchMethodError，要么是没有引入dependency，要么是jar包冲突。在这里应该是servlet-api.jar有冲突。

用命令mvn dependency:tree查看项目所有dependencies，发现有以下依赖：

[INFO] | +- org.apache.hbase:hbase-server:jar:0.96.1.1-cdh5.0.2:compile
...
[INFO] | | +- org.mortbay.jetty:servlet-api-2.5:jar:6.1.14:compile
...
[INFO] | | +- org.apache.hadoop:hadoop-common:jar:2.3.0-cdh5.0.2:compile
...
[INFO] | | | +- javax.servlet:servlet-api:jar:2.5:compile
...

hbase-server中也有servlet-api的jar包，尝试将其移除：

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<dependency>
	<groupId>org.apache.hbase</groupId>
	<artifactId>hbase-server</artifactId>
	<version>0.96.1.1-cdh5.0.2</version>
	<exclusions>
		<exclusion>
			<groupId>org.mortbay.jetty</groupId>
			<artifactId>servlet-api-2.5</artifactId>
		</exclusion>
		<exclusion>
			<groupId>javax.servlet</groupId>
			<artifactId>servlet-api</artifactId>
		</exclusion>
	</exclusions>
</dependency>

运行成功。