1
我想通過Vaadin（Vaadin框架8）創建一個Web應用程序。建立一個Vaadin網絡應用程序與動態內容
我讀了幾頁文檔，但仍然有一個關於Vaadin應用程序結構的大問題。我的問題是我缺乏關於它背後的理論的某些東西，我會嘗試通過第一次嘗試代碼來暴露我的問題。我會很感激任何能夠幫助我理解Vaadin如何工作的東西。
我想創建一個網站，用戶可以註冊，登錄和註銷。
網站的GUI的結構是首頁那裏有點像一個按鈕或類似的東西做的登錄，如果用戶沒有登錄，如果用戶登錄，而不是登錄按鈕，它應該出現註銷按鈕。
首先，我有一個類延伸UI;在那個類中，我設置了servlet和init()方法。
在init()方法中，我開始創建VerticalLayout()，然後MenuBar和Panel（稱爲contentPanel）。然後，我創建了一個Navigator。我遇到的第一個問題是，我將導航器理解爲在不同頁面之間瀏覽的可能性;導航器的構造函數想要一個SingleComponentContainer，所以現在，我不知道如何在不同的網頁之間導航。對於我的例子，在構造函數中我使用面板：new Navigator(this, contentPanel);然後我添加不同的View，然後將出現在面板內。最後，我導航到Welcome頁面。
MyUI類：
public class MyUI extends UI {
/**
* Class that checks if the user is in the database
* and the psw inserted is correct
*/
public static Authentication AUTH;
public static User user = null;
@WebServlet(value = "/*", asyncSupported= true)
@VaadinServletConfiguration(productionMode = false, ui = MyUI.class)
public static class MyUIServlet extends VaadinServlet {
}
@Override
protected void init(VaadinRequest request) {
AUTH = new Authentication();
VaadinSession.getCurrent().setAttribute("user", user);
final VerticalLayout layout = new VerticalLayout();
layout.setMargin(true);
setContent(layout);
Panel contentPanel = new Panel("Main Panel");
contentPanel.setSizeFull();
new Navigator(this, contentPanel);
getNavigator().addView(LoginPage.NAME, LoginPage.class);
getNavigator().setErrorView(LoginPage.class);
getNavigator().addView(LogoutPage.NAME, LogoutPage.class);
getNavigator().addView(WelcomePage.NAME, WelcomePage.class);
MenuBar.Command welcome = new Command() {
@Override
public void menuSelected(MenuItem selectedItem) {
getNavigator().navigateTo(WelcomePage.NAME);
}
};
MenuBar.Command login = new Command() {
@Override
public void menuSelected(MenuItem selectedItem) {
getNavigator().navigateTo(LoginPage.NAME);
}
};
MenuBar.Command logout = new Command() {
@Override
public void menuSelected(MenuItem selectedItem) {
getNavigator().navigateTo(LogoutPage.NAME);
}
};
MenuBar mainMenu = new MenuBar();
mainMenu.addItem("Welcome", VaadinIcons.ARROW_CIRCLE_LEFT, welcome);
mainMenu.addItem("Login", VaadinIcons.ENTER, login);
mainMenu.addItem("Logout", VaadinIcons.EXIT, logout);
layout.addComponent(mainMenu);
layout.addComponent(contentPanel);
getNavigator().navigateTo(WelcomePage.NAME);
}
}
LoginPage類：
public class LoginPage extends VerticalLayout implements View {
private static final long serialVersionUID = 1L;
public static final String NAME = "loginpage";
public LoginPage(){
Panel panel = new Panel("Login");
panel.setSizeUndefined();
addComponent(panel);
FormLayout content = new FormLayout();
TextField username = new TextField("Username");
content.addComponent(username);
PasswordField password = new PasswordField("Password");
content.addComponent(password);
Button send = new Button("Enter");
send.addClickListener(new Button.ClickListener() {
private static final long serialVersionUID = 1L;
public void buttonClick(ClickEvent event) {
//The authenticate method will returns
//true if the credentials are correct
//false otherwise
if(MyUI.AUTH.authenticate(username.getValue(), password.getValue())){
//In AUTH there is a User field called "user"
//User is a class that represents an user (so it has mail, psw, name etc)
VaadinSession.getCurrent().setAttribute("user", MyUI.AUTH.getUser());
}else{
Notification.show("Invalid credentials", Notification.Type.ERROR_MESSAGE);
}
}
});
content.addComponent(send);
content.setSizeUndefined();
content.setMargin(true);
panel.setContent(content);
setComponentAlignment(panel, Alignment.MIDDLE_CENTER);
}
}
註銷類有登錄類的相同的結構;有一個註銷方法：
private void doLogout() {
MyUI.AUTH.setUser(null);
VaadinSession.getCurrent().setAttribute("user", MyUI.AUTH.getUser());
getSession().close();
}
另一個問題是：我怎麼能動態地添加組件在我的佈局，立足於用戶狀態（？登錄與否）
下一個問題是：我沒有了解如何有效地進行註銷。
我將添加完整的代碼以方便進行任何測試。
public class LogoutPage extends VerticalLayout implements View {
private static final long serialVersionUID = 1L;
public static final String NAME = "logoutpage";
public LogoutPage(){
Panel panel = new Panel("Logout");
panel.setSizeUndefined();
addComponent(panel);
Button logout = new Button("Logout");
logout.addClickListener(e -> doLogout());
addComponent(logout);
}
private void doLogout() {
MyUI.AUTH.setUser(null);
VaadinSession.getCurrent().setAttribute("user", MyUI.AUTH.getUser());
getSession().close();
}
}
______________________________________________________________________________
public class WelcomePage extends VerticalLayout implements View {
private static final long serialVersionUID = 1L;
public static final String NAME = "welcomepage";
public WelcomePage() {
setMargin(true);
setSpacing(true);
Label welcome = new Label("Welcome");
welcome.addStyleName("h1");
addComponent(welcome);
}
@Override
public void enter(ViewChangeEvent event) {
}
}
______________________________________________________________________________
public class Authentication {
private static User user = null;
//those fields should be in user; this is just a test
private String userID = "ID";
private String psw = "psw";
public Authentication() {
}
public void setUser(User user) {
Authentication.user = user;
}
public User getUser(){
return Authentication.user;
}
public Boolean authenticate(String userID, String psw){
if(userID == this.userID && psw == this.psw) {
user = new User();
return true;
}
return false;
}
}