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Question

When I want to see the detail page of my Book I will get my book and redirect it to my overviewpage. Now when I use the <h:link> he always gives the last item of my dataTable. When I use the <h:commandLink> everthing works fine. Now my question, why doesn't work the <h:link outcome="..."> when the 'same' code in <h:commandLink> will work?

Managed Bean

@Named(value = "bookController")
@SessionScoped
public class BookController implements Serializable {

@EJB private BookRepository dao;
private LibraryBook book = new LibraryBook();

...

public String getLibraryBook(String isbn)
{
    this.book = this.dao.getBook(isbn);
    return "bookOverview";
} 

...

}

Book.xhtml

<f:view>
        <h:form>
            <h:dataTable value="#{bookController.books}" var="item" class="table">
                <h:column>
                    <f:facet name="header">
                        <h:outputText value="Isbn"/>
                    </f:facet>
                    <h:link value="#{item.isbn}" outcome="#{bookController.getLibraryBook(item.isbn)}"/>
                </h:column>
                <h:column>
                    <f:facet name="header">
                        <h:outputText value="Title"/>
                    </f:facet>
                    <h:outputText value="#{item.title}"/>
                </h:column>
                <h:column>
                    <h:commandButton value='Update' class="btn btn-warning" action="#{bookController.EditBook(item)}"></h:commandButton>
                    <h:commandButton value='Delete' class="btn btn-danger" action="#{bookController.deleteBook(item.isbn)}"></h:commandButton>
                </h:column>
            </h:dataTable>
        </h:form>
    </f:view>

score 3 · Accepted Answer · edited Jun 20 '20 at 09:12

Because the <h:link outcome> is evaluated at the moment the page is rendered, not when you click the link. The method you're referring in outcome sets the session scoped bean property to the current item and then returns a string bookOverview. So, effectively you end up with every single link having a outcome="bookOverview" before you click on it. In the meanwhile, the bean has only the last item remembered.

The <h:commandLink action> works because it is evaluated after you click the link.

This difference is because <h:link> is intented for idempotent (GET) requests which does not require a stateful <h:form>, and the <h:commandLink> is intented for non-idempotent (POST) requests which require a stateful <h:form>.

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