Tomcat中的Java JSP内部服务器错误

Question

任何人都可以帮我解决这个错误：

HTTP Status 500 - An exception occurred processing JSP page /LoginPage.jsp at line 45
Exception report
An exception occurred processing JSP page /LoginPage.jsp at line 45
The server encountered an internal error that prevented it from fulfilling this request.


org.apache.jasper.JasperException: An exception occurred processing JSP page /LoginPage.jsp at line 45

42:             }
43: 
44:             // Here you put the check on the username and password
45:             if (username.toLowerCase().trim().equals("admin") && password.toLowerCase().trim().equals("admin")) {
46:                 out.println("Welcome " + username + " <a href=\"index.jsp\">Back to main</a>");
47:                 session.setAttribute("username", username);
48:             }


Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)