异常信息如下：

[org.springframework.web.context.ContextLoader]Context initialization failed
org.springframework.beans.factory.CannotLoadBeanClassException: Error loading class [com.baikeyang.service.bike.impl.XABikeServiceImpl] for bean with name 'xaBikeService' defined in file [D:\Develop\Tomcat\apache-tomcat-7.0.40\wtpwebapps\youth\WEB-INF\classes\com\baikeyang\service\bike\impl\XABikeServiceImpl.class]: problem with class file or dependent class; nested exception is java.lang.UnsupportedClassVersionError: com/baikeyang/service/bike/impl/XABikeServiceImpl : Unsupported major.minor version 51.0 (unable to load class com.baikeyang.service.bike.impl.XABikeServiceImpl)
     at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1355)
     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:628)
     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:597)
     at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1445)
     at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:975)
     at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:752)
     at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
     at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
     at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444)
     at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326)
     at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
     at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4887)
     at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5381)
     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$Sync.innerRun(FutureTask.java:303)
     at java.util.concurrent.FutureTask.run(FutureTask.java:138)
     at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
     at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.UnsupportedClassVersionError: com/baikeyang/service/bike/impl/XABikeServiceImpl : Unsupported major.minor version 51.0 (unable to load class com.baikeyang.service.bike.impl.XABikeServiceImpl)
     at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2899)
     at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1173)
     at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1681)
     at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
     at org.springframework.util.ClassUtils.forName(ClassUtils.java:250)
     at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:394)
     at org.springframework.beans.factory.support.AbstractBeanFactory.doResolveBeanClass(AbstractBeanFactory.java:1397)
     at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1344)
     ... 20 more

JDK 编译器版本	target 参数	十六进制 minor.major	十进制 minor.major
jdk1.1.8	不能带 target 参数	00 03   00 2D	45.3
jdk1.2.2	不带(默认为 -target 1.1)	00 03   00 2D	45.3
jdk1.2.2	-target 1.2	00 00   00 2E	46.0
jdk1.3.1_19	不带(默认为 -target 1.1)	00 03   00 2D	45.3
jdk1.3.1_19	-target 1.3	00 00   00 2F	47.0
j2sdk1.4.2_10	不带(默认为 -target 1.2)	00 00   00 2E	46.0
j2sdk1.4.2_10	-target 1.4	00 00   00 30	48.0
jdk1.5.0_11	不带(默认为 -target 1.5)	00 00   00 31	49.0
jdk1.5.0_11	-target 1.4 -source 1.4	00 00   00 30	48.0
jdk1.6.0_01	不带(默认为 -target 1.6)	00 00   00 32	50.0
jdk1.6.0_01	-target 1.5	00 00   00 31	49.0
jdk1.6.0_01	-target 1.4 -source 1.4	00 00   00 30	48.0
jdk1.7.0	不带(默认为 -target 1.6)	00 00   00 32	50.0
jdk1.7.0	-target 1.7	00 00   00 33	51.0
jdk1.7.0	-target 1.4 -source 1.4	00 00   00 30	48.0

关于major.minor更多的信息大家可以去的Oracle官网去查看哦。

这个异常是由于 开发项目下使用的jdk版本和项目运行服务器jdk版本不同 而导致。解决方式就是使开发项目JDK版本和运行服务器的JDK版本保持一致。在这里就以我自己机子的Eclipse 和 Tomcat 为例来进行说明了。

1、设置Eclipse的JDK为1.7

2、设置项目的 java compiler改为jdk1.7

修改项目java compiler的方法：在项目点右键->选择Perperties->在出现的菜单中选择Java Compiler->最上面选中Enable project Specific setting->然后将jdk改为jdk1.7->完成。

3、设置Tomcat的JDK版本（如果配置了Java的环境变量且环境变量中配置的Java版本也是1.7时，不用进行第三步的操作也是可以运行的。当然，我的机子上可以并不能保证所有机子都有效，因为每人机子配置都有些差异性。所以我还是建议各位按照第三步操作配置，以防万一嘛。）：

搞定，然后重新编译下你的项目，Tomcat启动成功，无异常提示。