请问这是什么错误？

[kln78]

我在webapps下建立了helloapp虚拟目录，目录下有login.jsp,只是一个登陆页面。
打127.0.0.1/helloapp/login.jsp出现以下错误。编译不了
但我以把系统变量path中加入了%java_home%\bin
type Exception report

message

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

exception

org.apache.jasper.JasperException: Unable to compile class for JSP

No Java compiler was found to compile the generated source for the JSP.
This can usually be solved by copying manually $JAVA_HOME/lib/tools.jar from the JDK
to the common/lib directory of the Tomcat server, followed by a Tomcat restart.
If using an alternate Java compiler, please check its installation and access path.

org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:128)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:351)
org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:413)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:453)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:437)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:555)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:291)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
我把j2sdk与tomcat安装在不同的盘里，是否有关系？

[dropship]

This can usually be solved by copying manually $JAVA_HOME/lib/tools.jar from the JDK
to the common/lib directory of the Tomcat server, followed by a Tomcat restart.

看看这段话就明白了