JREのバージョンが違うとこんなエラー

JDK6でコンパイルしたWARファイルをJDK５の環境で実行させたらこんなエラー。
JDKを更新したの忘れてた。

JDK5でコンパイルしなおすか、JDK6のコンパイルオプションでJDK5互換で動作するようにコンパイルしなおすこと。

java.lang.UnsupportedClassVersionError: Bad version number in .class file
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
        at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1853)
        at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:875)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1330)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1209)
        at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:207)
        at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:302)
        at org.apache.catalina.core.ApplicationFilterConfig.(ApplicationFilterConfig.java:78)
        at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3635)
        at org.apache.catalina.core.StandardContext.start(StandardContext.java:4222)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544)
        at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:626)
        at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:553)
        at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:488)
        at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1149)
        at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
        at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022)
        at org.apache.catalina.core.StandardHost.start(StandardHost.java:736)
        at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014)
        at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
        at org.apache.catalina.core.StandardService.start(StandardService.java:448)
        at org.apache.catalina.core.StandardServer.start(StandardServer.java:700)
        at org.apache.catalina.startup.Catalina.start(Catalina.java:552)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295)
        at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433)

以上