会话属性问题 Vaadin 24

Question

我无法理解 VaadinSessions 和 UI 的工作原理。

我的类获取 SampleClient 的 id 和其他信息并将其用作 URL：

@Route(value = "URL-of-page/:sampleClientID?", layout = MainLayout.class)
@RolesAllowed("USER")
public class DocumentazioneEntita extends Div implements BeforeEnterObserver {
    
    @Override
    public void beforeEnter(BeforeEnterEvent event) {
        this.client = (SampleClient) VaadinSession.getCurrent().getAttribute("client");
        System.out.println("client inside override " + client);
        if (this.client == null) {
            Notification.show("No client selected", 3000, Notification.Position.BOTTOM_START);
            navigateToMain(event);
            return;
        }
        this.idClienteString = (String) VaadinSession.getCurrent().getAttribute("idCliente");
        System.out.println("ID CLIENT STRING: " + idClienteString);
        Optional<Long> sampleClientId = event.getRouteParameters().get(SAMPLECLIENT_ID).map(Long::parseLong);
        if (sampleClientId.isPresent()) {
            Optional<SampleClient> sampleClientFromBackend = sampleClientService.get(sampleClientId.get());
            if (sampleClientFromBackend.isPresent()) {
                populateForm(sampleClientFromBackend.get());
            } else {
                Notification.show(
                        String.format("Client not found, ID = %d", sampleClientId.get()),
                        3000, Notification.Position.BOTTOM_START);
                navigateToMain(event);
                return;
            }
            refreshGridData();
        } 
    }
    private Long idCliente = (Long) VaadinSession.getCurrent().getAttribute("IdCliente");
  
    
    private SampleCoursesService sampleCoursesService;
    private SampleContactsService sampleContactsService;
    private SampleClientService sampleClientService;
    private SampleContacts contact;
    private SampleClient client;
    
    private String SAMPLECLIENT_ID = "sampleClientID";


    private Checkbox showArchivedCheckbox; // Define showArchivedCheckbox as a field
    private Grid<SampleContacts> dispositiviTable = new Grid<>(SampleContacts.class);; // Define dispositiviTable as a field
    private List<SampleContacts> contactsList; // Define contactsList as a field

    private Binder<SampleClient> binder = new Binder<>(SampleClient.class);

    private GenerateReport generateReport;
    public String idClienteString;
    

        public DocumentazioneEntita(SampleCoursesService sampleCoursesService, 
                                    SampleContactsService sampleContactsService, 
                                    SampleClientService sampleClientService, GenerateReport generateReport) {
            this.sampleCoursesService = sampleCoursesService;
            this.sampleContactsService = sampleContactsService;
            this.sampleClientService = sampleClientService;
            this.generateReport = generateReport;
            
            setId("documentazione-entita-view");
            setSizeFull();
            System.out.println("ID CLIENTE: " + idCliente); 
            System.out.println("ID CLIENTE STRING: sotto autowired " + idClienteString);

为了更好地了解情况，我开始调试在控制台中打印我拥有的数据。 这是我终端的输出：

ID CLIENTE: 1
ID CLIENTE STRING: sotto autowired null

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA SampleClient [capCliente=null, cfCliente=XYZ789, descrizioneCliente=null, [email protected], idCliente=37, indirizzoCliente=789 Main St, insolvente=false, localitaCliente=New York, nomeCliente=John Smith, noteCliente=null, provinciaCliente=null, pivaCliente=1.23456789E8, sdiCliente=SDI123, telefonoCliente=1234567890]       
ID CLIENTE STRING: 37

所以在

 @Override

里面我有我的数据，在外面我没有。这是为什么呢？
我希望能够在我的页面中自由使用 SampleClient 的数据，但我不明白为什么它只保留在进入类之前。

值得注意的是，在上一页中我通过 Vaadin UI 获取了所有必要的信息：

   private void navigateToEntityDocumentation(SampleClient client) {
        System.out.println("go to: " + client);
        if (client != null) {
            Long idCliente = client.getIdCliente();
            
            if (idCliente != null) {
                
                String idClienteString = idCliente.toString();
                UI.getCurrent().navigate("documentazione-entita/" + idClienteString);
                UI.getCurrent().getSession().setAttribute("idCliente", idClienteString);
                UI.getCurrent().getSession().setAttribute("client", client); 
            } else {
                // Log that idCliente is null
                System.out.println("Cliente not found " + client);
                UI.getCurrent().navigate("#");
            }
        } else {
            // Log that client is null
            System.out.println("Client does not exists");
            UI.getCurrent().navigate("#");
        }
    }

这就是我的

System.out.println("go to: " + client);

在终端中输出的内容，作为我拥有从一个页面到另一个页面的数据流的证明。

go to: SampleClient [capCliente=null, cfCliente=XYZ789, descrizioneCliente=null, [email protected], idCliente=37, indirizzoCliente=789 Main St, insolvente=false, localitaCliente=New York, nomeCliente=John Smith, noteCliente=null, provinciaCliente=null, pivaCliente=1.23456789E8, sdiCliente=SDI123, telefonoCliente=1234567890]

Answer 1

正如评论中指出的，这里的问题与

VaadinSession

无关。

相反，问题在于代码的一部分使用

"IdCliente"

作为会话属性名称，而代码的另一部分使用

"idCliente"

。建议对像这样的魔术字符串值使用常量，以避免此类错误。