java - How to display many to many jpa collection in jsf?

Question

i made many to many join table between users and groups tables . so i have a collection in each entitie ( Users and groups )

@ManyToMany(mappedBy = "usersCollection")
    private Collection<Groups> groupsCollection;

and i want to display groups collection in Jsf thats what i did :

<p:dataTable var="user" value="#{usergestion.tableusers}">  
                           <p:column headerText="username">  
                               <h:outputText value="#{user.username}" />  
                           </p:column>  

                           <p:column headerText="nom">  
                               <h:outputText value="#{user.nom}" />  
                           </p:column>  

                           <p:column headerText="prenom">  
                               <h:outputText value="#{user.prenom}" />  
                           </p:column>

                            <p:column headerText="groupe"> 

                                <h:outputText value="#{user.groupsCollection.get(0)}"  />

                           </p:column>

and that what i get :

how i can get just the nombre not com.database.Groups[ idGroups=2 ] ???

Solution :

i used : <h:outputText value="#{user.groupsCollection.get(0).groupname}" />

question from:https://stackoverflow.com/questions/65599625/how-to-display-a-list-of-elements-in-a-cell-in-a-jsf

Answer 1

You normally use an iterating component such as <ui:repeat> or <h:dataTable> to iterate over a collection. You can perfectly nest it inside another iterating component.

E.g.

<p:column headerText="groupe"> 
    <ui:repeat value="#{user.groupsCollection}" var="groups">
        <h:outputText value="#{groups.groupname}" /><br/>
    </ui:repeat>
</p:column>

---

Unrelated to the concrete problem, you've there some poor naming convention. One group should be represented by a class named Group, not Groups. I suggest to rename the one and other so that the code becomes so much more self documenting:

<p:column headerText="groups"> 
    <ui:repeat value="#{user.groups}" var="group">
        <h:outputText value="#{group.name}" /><br/>
    </ui:repeat>
</p:column>

The plural s in the field/variable name should already be indicative that it concerns a collection.