java - Vaadin 表 - AddNestedContainerProperty

Question

public class LocationBasedRole extends AbstractEntity{
    @ManyToMany(fetch=FetchType.LAZY)
    private Set<Role> roles=new HashSet<Role>();

    @ManyToMany(fetch=FetchType.LAZY)
    private Set<Location> locations=new HashSet<Location>();
}


public class Role extends AbstractEntity{
    private String name;
}


public class Location extends AbstractEntity{
    private String location;
}

我有一个名为 locationBasedRole 的实体，它有 2 个名为 Roles 和 Locations 的属性。角色和位置都与 locationBasedRole 具有 @ManyToMany 关系。
现在我想在 Vaadin 表中拥有每个属性的一个属性。
应该是这样的，

public class UserForm extends OgsAbstractForm<User>{

    MTable<LocationBasedRole> locationBasedRoleTable = new MTable<LocationBasedRole>().withHeight("100%").withWidth("100%");


    @Override
    protected Component createContent() {

        Set<LocationBasedRole> lbRoles=new HashSet<LocationBasedRole>();
        roles.addAll(locationBasedRoleFasade.findAll());

        BeanItemContainer<LocationBasedRole> bean=new BeanItemContainer<LocationBasedRole>(LocationBasedRole.class);

        //It returns an error on the next both lines and I know the reason, but don't know how to solve it.
        // If it was no ManyToMany relation and the properties weren't a collection, it would work
        bean.addNestedContainerProperty("roles.name");
        bean.addNestedContainerProperty("locations.location");

        bean.removeContainerProperty("persistent");
        bean.removeContainerProperty("id");

        bean.addAll(lbRoles);

        locationBasedRoleTable.setContainerDataSource(bean);

        return new VerticalLayout(locationBasedRoleTable);
    }
}

当我从 NestedContainerProperties 中删除属性时，它至少会在表中显示一些内容。

bean.addNestedContainerProperty("roles");
bean.addNestedContainerProperty("locations");

我需要任何帮助!

提前致谢!

Answer 1

所以，如果我理解你的问题是正确的，你希望将 BeanItemContainer-Entity 的集合显示在每一列中吗？

我认为有两种可能性。

选项 1 - 对 Set 使用包装类并使用 addNestedContainerBean

一种可能是不在 LocationBasedRole 中使用 Set，而是使用扩展 HashSet 的包装类。然后您可以使用 addNestedContainerBean 方法。

我与 BeanItemContainer-Entity 团队创建了一个小示例

public class Team {

    private String teamName;
    private Members teamMembers;

    public String getTeamName() {
        return teamName;
    }

    public void setTeamName(String teamName) {
        this.teamName = teamName;
    }

    public Members getTeamMembers() {
        return teamMembers;
    }

    public void setTeamMembers(Members teamMembers) {
        this.teamMembers = teamMembers;
    }
}

由姓名和团队成员组成。后者的类型为Members:

public class Members extends HashSet<TeamMember> {

    public String getMembers() {
        return this.stream()
                .map(member -> member.getFirstName() + " " + member.getLastName())
                .collect(Collectors.joining(","));
    }

}

这是 Set 的简单包装器，其中包含 TeamMember 的实例:

public class TeamMember {

    private String firstName;
    private String lastName;
    private Integer age;

    // getters and setters
}

正如您在 Members 类中看到的，有一个方法 getMembers 返回一个字符串，其中包含以逗号分隔的团队成员姓名列表。

如果我们现在使用 addNestedContainerBean("teamMembers") Vaadin 会尝试显示 Members 类中包含的所有属性。 Vaadin 会认为 getMembers 是名为 Members 的 String 属性的 getter，因此会为其生成一列。

Vaadin 还会显示“空”列，因为它会找到 Set 的 isEmpty 方法，并认为 empty 是要在列中显示的属性。因此我们告诉 Vaadin 删除该列。

我的示例的最终代码如下所示:

protected Component createContent() {

        Set<Team> teams=new HashSet<>();
        for (int teamCounter = 0; teamCounter < 5; teamCounter++) {
            Team team = createTeam();
            addMembersToTeam(5, team);
            teams.add(team);
        }

        BeanItemContainer<Team> bean=new BeanItemContainer<>(Team.class);

        bean.addNestedContainerBean("teamMembers");
        bean.removeContainerProperty("teamMembers.empty");

        bean.addAll(teams);

        teamTable.setContainerDataSource(bean);

        return new VerticalLayout(teamTable);
    }

结果如下:

选项 2 - 创建假 getter 并使用 addNestedContainerProperty

为此，您唯一要做的就是扩展您的 BeanItemContainer-Entity (LocationBasedRole) 并为您想要在列中显示的每个 Set 创建一个假 getter。在您的示例中，这两个假 getter 可能是 public String getTheRoles() 和 public String getTheLocations()。然后您可以使用 bean.addNestedContainerProperty("theRoles") 和 bean.addNestedContainerProperty("theLocations")。

在我的示例中，我的 TeamMember 类(与您的 Role/Location 类相对应)仍然类似于上面的选项:

 public class TeamMember {

    private String firstName;
    private String lastName;
    private Integer age;

    // getters and setters
}

我的Team类(您的LocationBasedRole)看起来像:

public class Team {

    private String teamName;
    private Set<TeamMember> teamMembers;

    public String getTeamName() {
        return teamName;
    }

    public void setTeamName(String teamName) {
        this.teamName = teamName;
    }

    public Set<TeamMember> getTeamMembers() {
        return teamMembers;
    }

    public void setTeamMembers(Set<TeamMember> teamMembers) {
        this.teamMembers = teamMembers;
    }

    public String getMembers() {
        if (teamMembers != null) {
            return teamMembers.stream()
                    .map(member -> member.getFirstName() + " " + member.getLastName())
                    .collect(Collectors.joining(","));
        } else {
            return "No members";
        }
    }
}

现在您可以告诉 vaadin 添加(不存在的)属性“members”，Vaadin 将找到 getter getMembers 并使用它来生成列。我们还必须告诉 vaadin 不要显示原始的“teamMembers”属性。所以最终的代码是:

protected Component createContent() {

    Set<Team> teams=new HashSet<>();
    for (int teamCounter = 0; teamCounter < 5; teamCounter++) {
        Team team = createTeam();
        addMembersToTeam(5, team);
        teams.add(team);
    }

    BeanItemContainer<Team> bean=new BeanItemContainer<>(Team.class);

    bean.addNestedContainerProperty("members");
    bean.removeContainerProperty("teamMembers");

    bean.addAll(teams);

    teamTable.setContainerDataSource(bean);

    return new VerticalLayout(teamTable);
}

结果如下: