JavaEE servlet setAttribute 的用途

Question

希望大家能帮我理解servlet方法doGet中的case。

例如，我们有一个用户class，名字和姓氏，当然getters和setters都设置好了。附加信息位于代码的注释中。问题是，在这种情况下 SetAttribute 的目的是什么？我应该使用它吗？打开和关闭时我看不出有什么区别。预先感谢您的及时回复。

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    //here I initiate servlet to create a session yes?
    HttpSession session = request.getSession(true);
    // here im getting atribiute which is goinna be null now:
    User user = (User) session.getAttribute("user");



    //now in case of null i want to create object which can have null atributes like name and lastname:
    if(user == null) {

        user = createUser(request);

        //here is my problem, i dont know what is it for? I already get atrributes, why would i want to set object again? to what?
        session.setAttribute("user", user);
    }

    returnInfo(response,user);




}

protected User createUser(HttpServletRequest request) {
    User user = new User();
    String name = request.getParameter("name");
    String lastname = request.getParameter("lastname");

    user.setName(name);
    user.setSurname(lastname);
    return user;
}

protected void returnInfo(HttpServletResponse response,User user) throws IOException {
    PrintWriter write = response.getWriter();
    write.println("<html>");
    write.println("<body>");
    write.println("<div>");
    if(user.getName() == null && user.getSurname() == null) {
        write.println("no person was added");
    }
    else{
        write.println("person is" + " " + user.getName() + " " + user.getSurname());
    }

    write.println("</div>");
    write.println("</body>");
    write.println("</html>");
}

Answer 1

您刚刚创建了一个新用户。它必须添加到会话中，否则您的用户属性将始终为空。

JavaEE servlet setAttribute 的用途

JavaEE servlet setAttribute what for

servlets

jakarta-ee

request

response

setattribute