我有一个从HTML下拉页面获取参数的servlet。在按钮上单击,数据将发送到servlet。它在第一次发送数据时有效,但是如果我留在页面上并从下拉列表中选择不同的值 并单击提交按钮,新数据未设置到会话变量中。
我的servlet在下面。我是否需要修改DoGet
方法?同样,它第一次工作,但会话变量之后不会改变。
@WebServlet("/ListStudentServlet")
public class ListStudentServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public ListStudentServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String sessid = request.getParameter("studentid");
ArrayList<FactStudentDataBean> result = new ArrayList<>();
try ( Connection con = JdbcUtil.getConnection()) {
String sql= "select F.Sessionid "
+ "from FACT_STUDENT F "
+ "where studentid = '"+sessid+"';";
try (Statement st = con.createStatement()) {
ResultSet rs = st.executeQuery(sql);
while (rs.next()){
result.add(new FactStudentDataBean(rs.getString(1)));
}
for (FactStudentDataBean factStudentDataBean : result) {
sessid = factStudentDataBean.getSessid();
}
} catch (Exception e) {
e.printStackTrace();
}
}
catch (Exception e) {
e.printStackTrace();
}
//Trying to set the session variable below, works the first time but anything after doesn't change
HttpSession session = request.getSession(true);
session.setAttribute("sessid", sessid);
}
}
答案 0 :(得分:0)
你的代码有点&#34;脏&#34;。首先:你为什么要编写这样的SQL查询?:
String sql= "select F.Sessionid "
+ "from FACT_STUDENT F "
+ "where studentid = '"+sessid+"';";
而不是这样?:
String sql= "select F.Sessionid from FACT_STUDENT F where studentid = '"+sessid+"';";
第二:始终尝试使用prepareStatement
代替createStatement
(有关我所说的内容的解释,请参阅此问题:prepareStatement vs executeStatement)
现在回答:我想你必须使用session.getAttribute("sessid", sessid);
答案 1 :(得分:-1)
检查您在服务器端获得的jsessionid值。如果两者都不同,那么尝试通过传递false而不是true来获取会话。
request.getSession(false);
还可以转到tomcat manager应用程序并监视活动会话。
希望这会有所帮助。