学习Struts(1)-郁闷的第一步，环境问题

今天有点心血来潮，突然想自己整个struts的应用学习一下，于是拿来前阵子买的《精通struts：基于MVC的Java Web设计与开发》，看到第二章，有个非常简单的例子，因此觉得拿来上手。
启动tomcat5.0.19，在地址栏输入http://localhost:8080/helloapp/，......居然显示了一页编译错误，很是郁闷。
错误信息如下：

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...

开始查找原因，设置了环境变量后，重新启动了tomcat，结果错误依旧，痛苦万分~
上google，果然好用，一下就找到了解决方法：
        

1. Make sure the following environment variables are set correctly:   >>> JAVA_HOME points to "C:/j2sdk1.4.2" (correct folder if changed)                            >>> CLASSPATH points to %JAVA_HOME%/lib                                                        >>> PATH points to %JAVA_HOME%/bin                                                             2. copy $JAVA_HOME/lib/tools.jar to the common/lib directory of the Tomcat server              3. Update your registry to reflect the new JVM location:                                       key:  HKEY_LOCAL_MACHINE/SYSTEM/ControlSet001/Services/Apache                                  Tomcat/Parameters/JVM Library                                                                  value:      C:/j2sdk1.4.2/jre/bin/server/jvm.dll