Question

eclipse运行JSP文件时出现的，是什么错误，如何解决

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:370)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

root cause java.lang.NullPointerException
org.apache.jsp.order_jsp._jspService(org.apache.jsp.order_jsp:52)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

note The full stack trace of the root cause is available in the
Apache Tomcat/5.5.9 logs.

Answer 1

NullPointerException
空指针异常

典型情况是

null.callSomeMethod();

你需要在调用对象的方法前检查是否为null的情况，避免上面的情况出现。

Answer 2

你的order.jsp:52行有个变量为空指针就是为null了，你注意逻辑判断一下