使用maven的tomcat插件启动时报错问题

1、最近在学习Apache下的一个权限框架shiro。在eclipse上建了一个web项目，使用maven引入对应的依赖。在spring和springMVC等配置都准备好后，准备跑一下JSP页面确保环境没问题，跑的时候使用的也是maven的tomcat7插件，在pom.xml的插件配置处配置如下：

	shiro
		
	
	
		
			org.apache.tomcat.maven
			tomcat7-maven-plugin
			
				8080
				/
				UTF-8
			
		
	

2、然后在eclipse中使用maven命令执行，如下：

clean tomcat7:run

3、此时报错，如下：

[INFO] Scanning for projects...
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for com.shiro.test.spring:shiro-test-spring:war:0.0.1-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.tomcat.maven:tomcat7-maven-plugin is missing. @ line 114, column 12
[WARNING] 
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING] 
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING] 
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building shiro-test-spring Maven Webapp 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ shiro-test-spring ---
[INFO] Deleting D:\WorkSpace\EclipseWorkSpace\shiro-test-spring\target
[INFO] 
[INFO] >>> tomcat7-maven-plugin:2.2:run (default-cli) > process-classes @ shiro-test-spring >>>
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ shiro-test-spring ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 2 resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ shiro-test-spring ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] <<< tomcat7-maven-plugin:2.2:run (default-cli) < process-classes @ shiro-test-spring <<<
[INFO] 
[INFO] --- tomcat7-maven-plugin:2.2:run (default-cli) @ shiro-test-spring ---
[INFO] Running war on http://localhost:8080/
[INFO] Creating Tomcat server configuration at D:\WorkSpace\EclipseWorkSpace\shiro-test-spring\target\tomcat
[INFO] create webapp with contextPath: 
一月 02, 2017 2:01:36 下午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["http-bio-8080"]
一月 02, 2017 2:01:36 下午 org.apache.catalina.core.StandardService startInternal
信息: Starting service Tomcat
一月 02, 2017 2:01:36 下午 org.apache.catalina.core.StandardEngine startInternal
信息: Starting Servlet Engine: Apache Tomcat/7.0.47
一月 02, 2017 2:01:38 下午 org.apache.catalina.core.ContainerBase startInternal
严重: 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:192)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:800)
	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:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	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.LinkageError: loader constraint violation: loader (instance of org/apache/catalina/loader/WebappClassLoader) previously initiated loading for a different type with name "javax/servlet/ServletContext"
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
	at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1191)
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1669)
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
	at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:167)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5423)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more

一月 02, 2017 2:01:38 下午 org.apache.catalina.core.ContainerBase startInternal
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost]]
	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.util.concurrent.FutureTask.get(FutureTask.java:192)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
	at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.startup.Tomcat.start(Tomcat.java:341)
	at org.apache.tomcat.maven.plugin.tomcat7.run.AbstractRunMojo.startContainer(AbstractRunMojo.java:1238)
	at org.apache.tomcat.maven.plugin.tomcat7.run.AbstractRunMojo.execute(AbstractRunMojo.java:592)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
	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:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1131)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:800)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.132 s
[INFO] Finished at: 2017-01-02T14:01:38+08:00
[INFO] Final Memory: 20M/336M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.tomcat.maven:tomcat7-maven-plugin:2.2:run (default-cli) on project shiro-test-spring: Could not start Tomcat: Failed to start component [StandardServer[-1]]: Failed to start component [StandardService[Tomcat]]: Failed to start component [StandardEngine[Tomcat]]: A child container failed during start -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

4、解决办法如下：

      javax.servlet
      servlet-api
      2.5
      provided

5、在pom.xml引入的web（如上面的servlet-api）相关的依赖时，需要加入 provided这个配置，意思是这个servlet-api的依赖包只在编译和测试时使用而不在运行时使用；因为web容器自身一般都会带这些依赖包，故配置上scope。假如不配置此项，启动tomcat时出现上述的异常，个人认为是由于我们自己在pom.xml引入的依赖跟web容器自己的一些依赖包冲突导致。

6、再次使用上面的命令启动tomcat，此时问题解决。