有TreeWiewDemo.war文件 放到webapps文件夹下 运行tomcat 可以自动解压缩 且可以生成CLASS文件，
使用：http://localhost:8080/TreeWiewDemo/dynamicTree.jsp 出现错误如下：
HTTP Status 500 -
--------------------------------------------
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
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)
root cause
java.lang.NullPointerException
book.treeview.Category.FromDb(Category.java:43)
book.treeview.Category. <init> (Category.java:17)
org.apache.jsp.dynamicTree_jsp._jspService(dynamicTree_jsp.java:60)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
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)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
这个是为什么
注：运行tomcat界面正常 运行自己写的HELLOWORD的JSP程序正常
本部署文件为征服AJAX那本书中第十四章的示例
谢谢
------解决方案--------------------
book.treeview.Category.FromDb(Category.java:43)
java.lang.NullPointerException
看这一句啊，空指针。
------解决方案--------------------
找到这个代码看看就知道了
代码迷推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.daimami.com/search?q=317