在 Vaadin 中将字符串设置为 LocalDate 转换器 Table

Question

继 "Learning Vaadin 7, Second Edition" 这本书之后，我现在正尝试在 table 中显示简单的 beans。然而，本书只涵盖了旧java.util.Dateclass的用法。我正在尝试使用转换器显示 LocalDate 属性。

我要显示的 bean（人）：

public class Person {

private long id;
private String firstName;
private String lastName;
private LocalDate birthdate;
private Gender gender;

// .. GETTERS & SETTERS

我写了一个 LocalDateToStringConverter，实现了 com.vaadin.data.util.converter.Converter。

package be.kapture.converters;

import com.vaadin.data.util.converter.Converter;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.Locale;

public class LocalDateToStringConverter implements Converter<String, LocalDate> {

    @Override
    public LocalDate convertToModel(String value, Class<? extends LocalDate> targetType, Locale locale) throws ConversionException {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy");
        try {
            return LocalDate.parse(value, formatter);

        } catch (DateTimeParseException ex) {
            return null;
        }
    }

    @Override
    public String convertToPresentation(LocalDate value, Class<? extends String> targetType, Locale locale) throws ConversionException {
        return value.toString();
    }

    @Override
    public Class<LocalDate> getModelType() {
        return LocalDate.class;
    }

    @Override
    public Class<String> getPresentationType() {
        return String.class;
    }
}

在 UI 中，这是我设置转换器的代码片段：

...
Table table = new Table("", container);
table.setConverter("birthdate", new LocalDateToStringConverter());

verticalLayout.addComponent(table);

'container' 是一个 BeanItemContainer，我在其中放置了一些示例 Person 对象。在我的浏览器中访问 Vaadin 应用程序时，出现以下异常：

jun 27, 2016 1:56:45 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [HelloVaadinServlet] in context with path [] threw exception [com.vaadin.server.ServiceException: com.vaadin.ui.Table$CacheUpdateException: Error during Table cache update. Additional causes not shown.] with root cause
com.vaadin.data.util.converter.Converter$ConversionException: Unable to convert value of type java.time.LocalDate to presentation type class java.lang.String. No converter is set and the types are not compatible.
    at com.vaadin.data.util.converter.ConverterUtil.convertFromModel(ConverterUtil.java:116)
    at com.vaadin.ui.AbstractField.convertFromModel(AbstractField.java:736)
    at com.vaadin.ui.AbstractField.convertFromModel(AbstractField.java:721)
    at com.vaadin.ui.AbstractField.setPropertyDataSource(AbstractField.java:657)
    at com.vaadin.ui.Table.bindPropertyToField(Table.java:4140)
    at com.vaadin.ui.Table.getPropertyValue(Table.java:4109)
    at com.vaadin.ui.Table.parseItemIdToCells(Table.java:2386)
    at com.vaadin.ui.Table.getVisibleCellsNoCache(Table.java:2225)
    at com.vaadin.ui.Table.refreshRenderedCells(Table.java:1745)
    at com.vaadin.ui.Table.refreshRowCache(Table.java:2691)
    at com.vaadin.ui.Table.containerItemSetChange(Table.java:4587)
    at com.vaadin.data.util.AbstractContainer.fireItemSetChange(AbstractContainer.java:242)
    at com.vaadin.data.util.AbstractInMemoryContainer.fireItemsAdded(AbstractInMemoryContainer.java:1012)
    at com.vaadin.data.util.AbstractInMemoryContainer.fireItemAdded(AbstractInMemoryContainer.java:994)
    at com.vaadin.data.util.AbstractInMemoryContainer.internalAddItemAtEnd(AbstractInMemoryContainer.java:884)
    at com.vaadin.data.util.AbstractBeanContainer.addItem(AbstractBeanContainer.java:533)
    at com.vaadin.data.util.AbstractBeanContainer.addBean(AbstractBeanContainer.java:598)
    at com.vaadin.data.util.BeanItemContainer.addItem(BeanItemContainer.java:227)
    at be.kapture.MyUI.init(MyUI.java:88)
    at com.vaadin.ui.UI.doInit(UI.java:682)
    at com.vaadin.server.communication.UIInitHandler.getBrowserDetailsUI(UIInitHandler.java:214)
    at com.vaadin.server.communication.UIInitHandler.synchronizedHandleRequest(UIInitHandler.java:74)
    at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41)
    at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1409)
    at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:364)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2508)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2497)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

为什么不注册 Converter 来进行 String 到 LocalDate 的转换（如果需要，反之亦然）？我试过在 Table.setConverter 方法中使用匿名内部 class 作为参数，结果相同。我在这里做错了什么？

更新（根据要求）：

这是完整的 UI 代码，其中使用了 Table、容器和转换器。注意：这是一个没有实际目标的 "HelloVaadin" 沙盒项目。它是专门为像这个问题这样的目的而设置的，试图将 Java 8 的 LocalDate 集成到 Vaadin 项目中。

package be.kapture;

import be.kapture.converters.LocalDateToDateConverter;
import be.kapture.converters.LocalDateToStringConverter;
import be.kapture.entities.Person;
import be.kapture.util.CustomFieldGroupFieldFactory;
import com.vaadin.annotations.*;
import com.vaadin.data.fieldgroup.FieldGroup;
import com.vaadin.data.util.BeanItem;
import com.vaadin.data.util.BeanItemContainer;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.*;

import javax.servlet.annotation.WebServlet;
import java.time.LocalDate;
import java.util.Arrays;

import static com.vaadin.data.Property.ValueChangeListener;


@Theme("mytheme")
@Widgetset("be.kapture.MyAppWidgetset")
@PreserveOnRefresh
@Title("Hello Vaadin!")

public class MyUI extends UI implements Window.CloseListener {

    private static final Person person1 = new Person(1L, "John", "DOE", LocalDate.of(70, 1, 1));
    private static final Person person2 = new Person(2L, "Jane", "doe", LocalDate.of(70, 1, 1));
    private static final Person person3 = new Person(3L, "jules", "winnf", LocalDate.of(48, 11, 21));
    private static final Person person4 = new Person(4L, "vincent", "Vega", LocalDate.of(54, 2, 17));

    private static final BeanItemContainer<Person> container = new BeanItemContainer<>(Person.class);

    static {
        container.addAll(Arrays.asList(person1, person2, person3, person4));
    }

    private final VerticalLayout verticalLayout = new VerticalLayout();

    @Override
    protected void init(VaadinRequest vaadinRequest) {

        Person person = new Person(1L);
        person.setFirstName("John");
        person.setLastName("Doe");
        person.setBirthdate(LocalDate.now());

        BeanItem<Person> beanItem = new BeanItem<>(person);

        FieldGroup group = new FieldGroup(beanItem);
        group.setFieldFactory(new CustomFieldGroupFieldFactory());

        Field<?> id = group.buildAndBind("id");
        Field<?> firstName = group.buildAndBind("firstName");
        Field<?> lastName = group.buildAndBind("lastName");

        Field<?> birthdate = group.buildAndBind("birthdate");

        Field<?> gender = group.buildAndBind("gender");

//        birthdate.setConverter(new LocalDateToDateConverter());
//        birthdate.setPropertyDataSource(item.getItemProperty("birthdate"));
//        FormLayout layout = new FormLayout(id, firstName, lastName,
//                birthdate);
//        layout.setMargin(true);
//        setContent(layout);

        verticalLayout.setMargin(true);
        verticalLayout.setSpacing(true);

        verticalLayout.addComponents(id, firstName, lastName, birthdate, gender);

         // Define a person which cannot exist
        Person nullPerson = new Person(-1L);
        nullPerson.setFirstName("Test");
        container.addItem(nullPerson);
        final ListSelect select = new ListSelect("", container);

        // Send events on directly when clicked
        select.setImmediate(true);

        // Handle the value of the person as null
        select.setNullSelectionItemId(nullPerson);
        select.setItemCaptionPropertyId("firstName");
        select.addValueChangeListener((ValueChangeListener) event -> System.out.println(select.getValue()));

        verticalLayout.addComponent(select);

        Table table = new Table("");
        table.setEditable(true);
        table.setConverter(LocalDateToDateConverter.class);
        table.setContainerDataSource(container);

        verticalLayout.addComponent(table);

        setContent( verticalLayout);
    }

    @Override
    public void windowClose(Window.CloseEvent e) {
        Notification.show("Window closed.");
    }

    @WebServlet(urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true)
    @VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
    public static class MyUIServlet extends VaadinServlet {
    }
}

Answer 1

我很好奇并想出了你的问题。 setConverter(Object, Converter) 方法只允许更改该列中的值向用户显示的方式（文本表示）。这就是为什么第二个参数的类型是 Converter<java.lang.String,?>.

在您的示例中，您在 table 中启用了编辑功能。这需要 Vaadin 知道它将如何为您的 LocalDate 列提供 table 单元格编辑器。默认情况下，table 不知道 LocalDate。我知道您有 2 个选项：

实施 converter factory，returns Converter LocalDate 至 String。然后 table 组件能够显示一个文本字段，您可以在其中根据转换器中的格式输入日期。我没有尝试用户输入无效字符串时发生的情况。
在 table 组件上实施 table field factory and call setTableFieldFactory。现场工厂会显示 PopupDateField 或类似的东西。这样你是类型安全的并且可以使用内置的日期字段。

IMO 后者会是一个更好的用户体验，但当然它在开发中需要更多的努力。

在 Vaadin 中将字符串设置为 LocalDate 转换器 Table

Setting a String to LocalDate converter in Vaadin Table

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