Question

org.apache.jasper.JasperException java.lang java.lang.NullPointerException 空指针错误

报错提示 各位大侠帮帮忙解决一下！
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: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:491)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

root cause

java.lang.NullPointerException
org.apache.jsp.shop_jsp._jspService(shop_jsp.java:102)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

Answer 1

朋友，你要学会追踪异常的来源才行啊，我解释给你听吧，希望能够帮到你，谢谢
org.apache.jasper.JasperException: java.lang.NullPointerException
这个空指针异常其实是由下面的空指针异常导致的，你只要解决下面那个，这里就不会有问题了
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:491)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

root cause

java.lang.NullPointerException
而这个空指针异常明显是由于你shop_jsp.java的102行导致的嘛，你在那里设置个断点，肯定是某个对象为空，你调用了他的属性或者方法才抛出这个异常的。如果不不会debug的话。那就在这行之前设置一个System.out.println(obj);在控制台输出这个对象看看是否为null。这里肯定是null的。
整个异常就这样追踪就可以了啊。
org.apache.jsp.shop_jsp._jspService(shop_jsp.java:102)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

Answer 2

在jsp的代码里面有实例为空。但你却调用了它的函数。去检查下shop.jsp吧。

Answer 3

jsp-api.jar 与tomcat中jar包冲突，删除jsp-api.jar即可

Answer 4

在你的shop.jsp中 对java代码进行debug.

Answer 5

跟踪问题根源...代码都没贴出来.怎么找错误.