Manipulating a List inside a foreach in a view

Question

I have a doubt that should be simple to solve, but I’m not able to develop a logic, or even may be doing it the wrong way.

Well, I have a table in which I go through a table called "categories" within this table I have a relationship with another called "destinations" as you can notice below in the bean:

Destination.java

@Entity
@Table(name="destination")
@Multitenant
@TenantDiscriminatorColumn(name="tenant_id", discriminatorType=DiscriminatorType.INTEGER, contextProperty=PersistenceUnitProperties.MULTITENANT_PROPERTY_DEFAULT)
@NamedQuery(name="Destination.findAll", query="SELECT d FROM Destination d")
public class Destination implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id_destination")
    private Long idDestination;

    @Column(name="tenant_id", insertable=false, updatable=false)
    private Long tenantId;

    @Column(name="appear_website")
    private Boolean dtAppearWebsite;

    @Lob
    @Column(name="description")
    private String dtDescription;

    @Column(name="highlight_website")
    private Boolean dtHighlightWebsite;

    @Column(name="name")
    private String dtName;

    @OneToOne(cascade=CascadeType.PERSIST)
    @JoinColumn(name="fk_streetview")
    private StreetView streetView;

    @OneToOne(cascade=CascadeType.PERSIST)
    @JoinColumn(name="fk_video")
    private Video video;

    @ManyToOne(cascade=CascadeType.REFRESH)
    @JoinColumn(name="fk_category")
    private Category categories;


    //Getters and Setters

Category.java

@Entity
@Table(name="category")
@Multitenant
@TenantDiscriminatorColumn(name="tenant_id", discriminatorType=DiscriminatorType.INTEGER, contextProperty=PersistenceUnitProperties.MULTITENANT_PROPERTY_DEFAULT)
@NamedQuery(name="Category.findAll", query="SELECT c FROM Category c")
public class Category implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id_category")
    private Long idCategory;

    @Column(name="ct_active")
    private int ctActive;

    @Column(name="ct_name")
    private String ctName;

    @Column(name="tenant_id", insertable=false, updatable=false)
    private Long tenantId;

    @OneToMany(mappedBy="categories")
    private Set<Destination> destination;

    //Getters and Setters

Right! In my view I have a field in which I have displayed the number of destinations linked to each category:

<c:forEach items="${category}" var="c">
    <tr>
        <td><a href="editCategory?id=${c.idCategory}">${c.ctName}</a></td>
        <!-- Campo no qual o numero de destinos é exibido por categoria-->
        <td>${categoryHasDestination}</td>
        <c:choose>
            <c:when test="${c.ctActive=='1'}">
                <td><span class="label label-success">Ativo</span></td>
            </c:when>
            <c:otherwise>
                <td><span class="label label-warning">Desativo</span></td>
            </c:otherwise>
        </c:choose>
    </tr>
</c:forEach>

So, I created a method in which returns the categories and also a list of the number of linked destinations in each category.

@RequestMapping("category")
public String getMenuCategory(Model mv) {
    List<Category> category = dashboardFacade.getCategoryList();
    List<Integer> size = new ArrayList<Integer>();

    for (Category categories : category) {
        Set<Destination> destinationList = categories.getDestination();
        int s = destinationList.size();
        size.add(s);
    }

    /Retorna uma lista com o numero de destinos para cada categoria
    mv.addAttribute("categoryHasDestination", size);

    //Me retorna todas as categorias
    mv.addAttribute("category", category);
    return "category/categoryList";
}

The problem is that in my view I have a foreach, IE, for each record the list is returned and not the number itself. The image below illustrates what I mean:

I thank you all for your help

Hug!

Answer 1

Create a method getDestinationSize in your class Category that returns the size of the attribute destination.

Then in your JSP, just access the method ${c.destinationSize}.

Answer 2

Using the forEach of jstl exists the attribute varStatus exposing an object of the type javax.servlet.jsp.jstl.core.LoopTagStatus in the iteration scope, which provides some data about the object being iterated.

In that case I’m using the index to index your list of categoryHasDestination to get the data you need.

<c:forEach items="${category}" var="c" varStatus="status">
    <tr>
        <td><a href="editCategory?id=${c.idCategory}">${c.ctName}</a></td>
        <!-- Campo no qual o numero de destinos é exibido por categoria-->
        <td>${categoryHasDestination[status.index]}</td>
        <c:choose>
            <c:when test="${c.ctActive=='1'}">
                <td><span class="label label-success">Ativo</span></td>
            </c:when>
            <c:otherwise>
                <td><span class="label label-warning">Desativo</span></td>
            </c:otherwise>
        </c:choose>
    </tr>
</c:forEach>

To see the other attributes of a look at the documentation of LoopTagStatus