当出现这样问题时，怎样解决呢，我弄了半天也没有搞好：
Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK
org.apache.tools.ant.taskdefs.compilers.CompilerAdapterFactory.getCompiler(CompilerAdapterFactory.java:105)
org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:929)
org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:758)
org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:407)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:497)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:476)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:464)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
将JDK安装目录下lib中的tools.jar拷贝到Tomcat的安装目录下common/lib目录下，重启Tomcat即可