UnsupportedClassVersionError 异常阻止 Tomcat 启动答案

【问题标题】：UnsupportedClassVersionError exception prevents Tomcat from startingUnsupportedClassVersionError 异常阻止 Tomcat 启动
【发布时间】：2014-04-06 00:14:41
【问题描述】：

子容器在启动过程中失败

java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/PersonalCalculator]]
    at java.util.concurrent.FutureTask$Sync.innerGet(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1128)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:782)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1566)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1556)
    at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/PersonalCalculator]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    ... 7 more
Caused by: java.lang.UnsupportedClassVersionError: servlets/CheckContacts : Unsupported major.minor version 51.0 (unable to load class servlets.CheckContacts)
    at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2893)
    at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1170)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1556)
    at org.apache.catalina.startup.WebAnnotationSet.loadClass(WebAnnotationSet.java:480)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:130)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:66)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:381)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:858)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:345)
    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:5161)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 7 more
Mar 4, 2014 3:51:29 AM 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[/p]]
    at java.util.concurrent.FutureTask$Sync.innerGet(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1128)
    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$StartChild.call(ContainerBase.java:1566)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1556)
    at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/p]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    ... 7 more
Caused by: java.lang.UnsupportedClassVersionError: com/servlets/AdminLogin : Unsupported major.minor version 51.0 (unable to load class com.servlets.AdminLogin)
    at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2893)
    at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1170)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1556)
    at org.apache.catalina.startup.WebAnnotationSet.loadClass(WebAnnotationSet.java:480)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:130)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:66)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:381)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:858)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:345)
    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:5161)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 7 more
Mar 4, 2014 3:51:29 AM 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$Sync.innerGet(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1128)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:675)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:450)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1566)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1556)
    at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1136)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:782)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 7 more
Mar 4, 2014 3:51:29 AM org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start: 
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:675)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    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:732)
    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:1136)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 11 more

【问题讨论】：

你不应该发你一辈子！！

标签： java eclipse tomcat servlets

【解决方案1】：

您的 lib 文件夹中有一个不兼容的类：

java.lang.UnsupportedClassVersionError: servlets/CheckContacts : Unsupported major.minor version 51.0

【讨论】：

【解决方案2】：

这可能是由于编译/运行时版本不兼容造成的。（你在编译你的类时使用了一个比运行它们时更高的一个）。因此，请在编译时检查使用的 jdk 版本，并在加载服务器时使用相同的版本。

【讨论】：

如何在编译和运行时检查 java 版本？
在编译时它是你在编译你的类时使用的那个，所以这取决于你是怎么做的或者你使用什么工具？在运行时它是 Tomcat AS 正在使用的一个，因此一个 catalina 进程正在使用（大多数时候它是 $JAVA_HOME 路径变量）。

【解决方案3】：

UnsupportedClassVersionError 表示您有一些代码使用较新的 JDK 编译，但运行在较旧的 JRE 上。在您的情况下，版本 51.0 指的是 Java7（您正在使用的某些库已被编译 - 在您的情况下，它看起来像 servlet API），并且您正在使用以前的版本运行，很可能是 Java6。

确保您使用的是 Java7，问题就会消失。

【讨论】：

先生，我正在使用 java1.7.0 .m 新手请帮我解决这个问题
不，您没有使用 java 1.7 - 至少没有安装那个 tomcat。 Java7（或 1.7）可以执行 51.0 版本的字节码，你的不能。检查您的 JAVA_HOME 环境变量，还检查它是否在 startup.[bat|sh]、setenv.[bat|sh] 或 catalina.[bat|sh] 中显式设置。还要检查你的tomcat旁边是否有一个jre目录，或者你是否安装了多个版本的java。另外，我希望 1.7.0 不是指“无补丁”，而是您处于当前的补丁级别，对（已经超过 50）

【解决方案4】：

使用正确的 JAVA_HOME 更新您的 ~/.profile 或 ~/.zshrc 文件

export JAVA_HOME="/path/to/java/jdk"
export PATH="$JAVA_HOME/bin/java:$PATH"

然后构建war文件并运行tomcat startup.sh

【讨论】：