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Tomcat 7(cuando se incluye un proyecto de servlet) no está mirando en 45 segundos... y aumentar el tiempo de espera no resuelve

Question

Tomcat 7 no está comenzando cuando se intenta ejecutar una aplicación web (con un servlet). El servidor funciona bien cuando solo tengo una página html. Pero cuando intento agregar un servlet y agregarlo a tomcat, el servidor no funciona. comienza y da un error que dice "Tomcat 7 no se inició en 45 segundos". Aumenté el tiempo de espera, pero no pasó nada. Por favor, ayúdame a resolver este problema

La consola dice:

"23 Jan, 2012 1:43:44 PM org.apache.catalina.core.AprLifecycleListener init
INFO: The APR based Apache Tomcat Native library which allows optimal performance in                  production environments was not found on the java.library.path: C:/Program Files (x86)/Java/jdk1.7.0/bin;.;C:/Windows/Sun/Java/bin;C:/Windows/system32;C:/Windows;C:/Program Files/Java/jdk1.6.0_23/jre/bin/server;C:/Program Files/Java/jdk1.6.0_23/jre/bin;C:/Program Files/Java/jdk1.6.0_23/jre/lib/amd64;C:/Program Files (x86)/Java/jdk1.7.0/jre/bin;F:/SOFTWARES/Eclipse Indigo/eclipse;
23 Jan, 2012 1:43:44 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property     ''source'' to ''org.eclipse.jst.jee.server:Basic'' did not find a matching property.
23 Jan, 2012 1:43:44 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-bio-80"]
23 Jan, 2012 1:43:44 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-bio-9999"]
23 Jan, 2012 1:43:44 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 717 ms
23 Jan, 2012 1:43:44 PM org.apache.catalina.core.StandardService startInternal
INFO: Starting service Catalina
23 Jan, 2012 1:43:44 PM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet Engine: Apache Tomcat/7.0.23
23 Jan, 2012 1:43:45 PM org.apache.catalina.core.ContainerBase startInternal
SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component     [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/Basic]]
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:252)
at java.util.concurrent.FutureTask.get(FutureTask.java:111)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1100)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:782)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1525)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1515)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:674)
    Caused by: org.apache.catalina.LifecycleException: Failed to start component     [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/Basic]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    ... 7 more
    Caused by: java.lang.UnsupportedClassVersionError: Simple : Unsupported major.minor version 51.0 (unable to load class Simple)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2827)
at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1160)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1655)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1533)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:108)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:58)
at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:338)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:831)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:302)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5148)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
23 Jan, 2012 1:43:45 PM org.apache.catalina.core.ContainerBase startInternal
SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to     start component [StandardEngine[Catalina].StandardHost[localhost]]
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:252)
at java.util.concurrent.FutureTask.get(FutureTask.java:111)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1100)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:291)
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:727)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.startup.Catalina.start(Catalina.java:624)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:623)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:450)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1525)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1515)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:674)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1108)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:782)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
23 Jan, 2012 1:43:45 PM org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start: 
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8000]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.startup.Catalina.start(Catalina.java:624)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:623)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:450)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:727)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component         [StandardEngine[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 9 more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1108)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:291)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 11 more
23 Jan, 2012 1:43:45 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 313 ms "    ''

Answer 1

Si acaba de copiar el mensaje de error de la causa de la excepción en Google, habría encontrado el problema. "Major.minor versión no soportada 51.0" significa que compiló las clases con JDK7, pero intenta implementarlo y ejecutarlo con una versión anterior de JDK o JRE. Comience su tomcat con JDK7, o cambie el JDK que está utilizando para compilar sus clases.

Nota al margen: su clase parece tener el nombre Simple y estar en el paquete predeterminado. Esto es una mala práctica que causará todo tipo de problemas. Siempre ponga sus clases en un paquete.