java - Session 对象中的 ArrayList 似乎丢失了内容

Question

我在从 session 中检索和转换 ArrayList 时遇到问题。我收到以下错误:

    javax.servlet.ServletException: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1

我将 arrayList 存储在 session 中:

    List<UserApplication> userList = uaDAO.searchUser(eds);
    if (!userList.isEmpty()) {
    request.getSession().setAttribute("userList", userList);
    action_forward = EDITSUCCESS;

为了将 session 对象转换为 ArrayList，执行以下操作:

    EditStudentForm edt = (EditStudentForm)form;
    if ((session.getAttribute("userList")) instanceof List){
    List <UserApplication> studtList = (ArrayList<UserApplication>)session.getAttribute("userList");
    }
    try {
    uaDAO.editUser(edt,studtList);
    action_forward = EDITSUCCESS;
    }

我在 DAO 类中遇到错误:

    public void editUser(EditStudentForm edt,List studtList) throws Exception {
    PreparedStatement pst = null;
    StringBuilder sb = new StringBuilder();
    int stCode =Integer.parseInt(studtList.get(1).toString());  GETTING ERROR HERE
    if (edt.getTitle() != null && !edt.getTitle().equals(studtList.get(2).toString())) {
    sb.append("title = '").append(edt.getTitle()).append("'");
    }
    .
    .

Answer 1

您明确要求列表中的第二个 (studtList.get(1)) 和第三个 (studtList.get(2)) 项目，但从未真正确定这个 list 足够大了。此外，您的代码显然甚至无法编译:

if ((session.getAttribute("userList")) instanceof List){
  List <UserApplication> studtList = ///...
}
try {
  uaDAO.editUser(edt,studtList);

studtList 在 try block 中无法访问，if 语句中的括号也不匹配。