JSP - HTTP 상태 500 - 내부 서버 오류

Question

아래는 내 .jsp의 일부입니다.

<%User user = (User) (session.getAttribute("user"));%> 
<b>Welcome <%= user.getFirstName() + " " + user.getLastName()%></b> 
<br/> 

그리고 오류가 아래에 무엇입니까 :

HTTP Status 500 – Internal Server Error

Type Exception Report

Message An exception occurred processing [/home.jsp] at line [20]

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception org.apache.jasper.JasperException: An exception occurred processing [/home.jsp] at line [20]

17: This is added information page
18: <%=new Date()%> 19: <%User user = (User) (session.getAttribute("user"));%> 20: Welcome <%= user.getFirstName() + " " + user.getLastName()%> 21:
22: 23: Logout

Stacktrace: org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:593) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:482) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329) javax.servlet.http.HttpServlet.service(HttpServlet.java:741) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

Root Cause java.lang.NullPointerException org.apache.jsp.home_jsp._jspService(home_jsp.java:139) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:741) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:444) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329) javax.servlet.http.HttpServlet.service(HttpServlet.java:741) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

Note The full stack trace of the root cause is available in the server logs.

Apache Tomcat/9.0.1

사람이 PLS 도와 드릴까요? 오류는 라인 20에 있습니다. user (= session.getAttribute("user"))이 null이기 때문에

Answer 1

NullPointerException이 발생합니다.

최소한 if (user != null) { ...을 추가해야합니다.