虚拟目录或web.xml配置问题？

我在server.xml下建了一个虚拟目录，我将jsp-examples拷贝到虚拟目录下运行正常。
但我自已写的一个one.jsp文件，放在webapps/jsp-exmples/运行正常，但放在虚拟目录中的运行出错，出错为：
HTTP Status 500 -

--------------------------------------------------------------------------------

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: com/sun/tools/javac/Main (Unsupported major.minor version 48.0)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:256)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)


root cause

java.lang.UnsupportedClassVersionError: com/sun/tools/javac/Main (Unsupported major.minor version 48.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:486)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:111)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:248)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at org.apache.catalina.loader.StandardClassLoader.findClass(StandardClassLoader.java:520)
at org.apache.catalina.loader.StandardClassLoader.loadClass(StandardClassLoader.java:857)
at org.apache.catalina.loader.StandardClassLoader.loadClass(StandardClassLoader.java:756)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:120)
at org.apache.tools.ant.taskdefs.compilers.CompilerAdapterFactory.doesModernCompilerExist(CompilerAdapterFactory.java:173)
at org.apache.tools.ant.taskdefs.compilers.CompilerAdapterFactory.getCompiler(CompilerAdapterFactory.java:131)
at org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:835)
at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:682)
at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:390)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:458)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:552)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:291)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)


note The full stack trace of the root cause is available in the Tomcat logs.

请问是什么原因？而且我没有配置web.xml文件。