Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
com.servlet.ServletB.doPost(ServletB.java:29)
com.servlet.ServletB.doGet(ServletB.java:22)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.
代码出现的错误的地方：
HttpSession session=request.getSession();
System.out.println(session.getAttribute("name"));
String name=session.getAttribute("name").toString();
String sessionid=session.getAttribute("sessionID").toString(); response.setContentType("text/html;charset=gbk");
response.setCharacterEncoding("gbk");
PrintWriter out=response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");//需要导入的JSP相关代码
out.println("<html>");
out.println("<head><title>获取session的相关属性</titel>");
out.println("</head>");
out.println("<body>");
out.println("session的name为："+name);
out.println("session的sessionid为："+sessionid);
out.println("</body>");
out.println("</html>");
out.flush();
out.close();
------解决方案--------------------------------------------------------
String sessionid=session.getAttribute("sessionID").toString();
改成：
String sessionid=(String)session.getAttribute("sessionID");