Question

JSP向Servlet传值

我写了个测试类：
MyJsp01.jsp
<form action="testRequestsetAttribute/MyJsp02.jsp" method="post">
<%
session.setAttribute("val","mark");
%>
<input type="submit" value="submit">
</form>

MyJsp02.jsp
<%=session.getAttribute("val") %>
<form action="testRequextGetAttribute" method="post">

<input type="submit" value="submit">
</form>

servlet:
HttpSession session = null;
String mark=session.getAttribute("mark").toString();
out.print(mark);

MyJsp01.jsp提交给MyJsp02.jsp，session值取到，MyJsp02.jsp提交给servlet，报空指针异常
异常行：String user=session.getAttribute("user").toString();

前辈们帮忙分析下原因
写错个地方：servlet取值getAttribute("val"),不是"mark"
异常行：String mark=session.getAttribute("val").toString();

Answer 1

HttpSession session = request.getSession();而不能HttpSession session = null;