Vaadin 7.0.1 带有 JPAContainer 和 FieldGroup 的组合框

（抱歉，如果这是一个新问题）

我有两个 JPAContainer，一个用于 Employee 类/表，一个用于语言类/表。员工可以选择一种语言。

我正在尝试创建一个员工编辑表单，其中包含用于语言选择的组合框和用于处理绑定和创建的 FieldGroup。

我可以通过 JPAContainer 获取下拉列表以包含语言表中的条目，但它不会显示员工记录中已有的值。我究竟做错了什么？

//Key parts of code....

private JPAContainer<Employee> employees;
private JPAContainer<Language> languages;

FormLayout formLayout = new FormLayout();

formFieldGroup = new FieldGroup(employeeItem);

Field<?> firstName = formFieldGroup.buildAndBind("First name", "firstName");
Field<?> lastName = formFieldGroup.buildAndBind("Last name", "lastName");
Field<?> userName = formFieldGroup.buildAndBind("Username", "userName");
Field<?> fullName = formFieldGroup.buildAndBind("Full name", "fullName");
Field<?> initials = formFieldGroup.buildAndBind("Initials", "initials");

ComboBox language = new ComboBox("Language",languages);
language.setContainerDataSource(languages);
language.setItemCaptionPropertyId("languageName");
language.setFilteringMode(FilteringMode.CONTAINS);
language.setImmediate(true);

formFieldGroup.bind(language, "language");

firstName.addValidator(new BeanValidator(Employee.class, "firstName"));
lastName.addValidator(new BeanValidator(Employee.class, "lastName"));
firstName.addValidator(new BeanValidator(Employee.class, "userName"));
lastName.addValidator(new BeanValidator(Employee.class, "fullName"));
lastName.addValidator(new BeanValidator(Employee.class, "initials"));

formLayout.addComponent(userName);
formLayout.addComponent(fullName);
formLayout.addComponent(firstName);
formLayout.addComponent(lastName);
formLayout.addComponent(initials);
formLayout.addComponent(language);

 // A few details of the domain classes
@Entity
@Table(name="Employees")
public class Employee   extends BaseEntity
{
private static final long   serialVersionUID    = 1L;

@Id 
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="EmployeeID")
private Integer     employeeID;

    ...

@ManyToOne 
@JoinColumn(name="LanguageID",updatable=false)
private Language    language;
    ...}

@Entity
@Table(name="Languages")
public class Language  extends BaseEntity
{

@Id 
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="LanguageID")
private Integer languageID;

@Column(name="LangaugeName")
private String  languageName;

    ... }

我通过 Vaadin 论坛收到了以下回答此问题的回复（感谢 Jonatan Kronqvist）。

嗨迈克尔，

JPAContainer项ID与数据库中的ID相同，即 意味着在选择/组合框中使用 JPAContainer 会导致该值 选择的 ID 是数据库中行的 ID，而不是 POJO 本身，正如您的 Employee 实体 POJO 所期望的那样。添加一个 SingleSelectConverter 到您的组合框应该可以解决您的问题：

language.setConverter(new SingleSelectConverter(language));

...

HTH，/乔纳坦