按照书＃34;学习Vaadin 7，Second Edition＆＃34;，我现在试图在表格中显示简单的豆子。但是，本书仅介绍旧java.util.Date类的用法。我试图使用转换器显示LocalDate属性。
我想要显示的bean（Person）：
public class Person {
private long id;
private String firstName;
private String lastName;
private LocalDate birthdate;
private Gender gender;
// .. GETTERS & SETTERS
我编写了一个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;
}
}
在用户界面中，这是我设置转换器的代码段：
...
Table table = new Table("", container);
table.setConverter("birthdate", new LocalDateToStringConverter());
verticalLayout.addComponent(table);
＆＃39;容器＆＃39;作为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，我得到以下例外：
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来执行String to LocalDate转换（反之亦然，如果需要的话）？我已经尝试使用匿名内部类作为Table.setConverter方法中的参数，结果相同。我在这里做错了什么？
更新（根据要求）：
以下是使用Table，Container和Converter的完整UI代码。注意：它是一个＆＃34; HelloVaadin＆＃34;没有实际目标的沙箱项目。它的设置特别适用于此类问题，尝试将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 {
}
}
答案 0 :(得分：1)
我好奇并想出了你的问题。方法setConverter(Object, Converter)只允许更改该列中的值显示给用户的方式（文本表示）。这就是为什么第二个参数的类型是~/.rbenv$ rbenv init -
。
在您的示例中，您启用了表格编辑功能。这要求Vaadin知道它将如何为您的Converter<java.lang.String,?>列提供表格单元格编辑器。默认情况下，该表不知道LocalDate。我知道你有两个选择：
LocalDate的{{1}}返回Converter。然后，表组件可以显示一个文本字段，您可以根据转换器中的格式输入日期。我没有尝试当用户输入无效字符串时发生的事情。LocalDate或类似的东西。这样您就可以使用类型安全的内容，并且可以使用内置的日期字段。IMO后者将是一个更好的用户体验，但当然是更多的开发工作。