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：

<build><finalName>shiro</finalName><!-- tomcat7 配置插件 --><plugins><plugin><groupId>org.apache.tomcat.maven</groupId><artifactId>tomcat7-maven-plugin</artifactId><configuration><port>8080</port><path>/</path><uriEncoding>UTF-8</uriEncoding></configuration></plugin></plugins></build>

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 startjava.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 moreCaused 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 startjava.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 startat 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：

<dependency><groupId>javax.servlet</groupId><artifactId>servlet-api</artifactId><version>2.5</version><scope>provided</scope></dependency>

5、在pom.xml引入的web（如上面的servlet-api）相关的依赖时，需要加入<scope>provided</scope>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。