tomcat error

what is this error?

Code:

HTTP Status 500 - 

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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:373)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:245)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


root cause 

java.lang.NullPointerException
	org.apache.jsp.prodotti_jsp._jspService(org.apache.jsp.prodotti_jsp:90)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:325)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:245)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


note The full stack trace of the root cause is available in the Apache Tomcat/5.5.7 logs.


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Apache Tomcat/5.5.7