如何使用commandButton在JSF中的页面之间导航？

Question

I have a list of Strings (in my case the names of Projects) displayed using JSF, with each String having a corresponding 'view' button created in JSF. When the user presses the view button, I want to navigate to a new page that shows a description for the project in question. This is achieved by passing the project_id through the method as shown below. I know how to navigate between JSF pages using faces-config by navigating based on the string returned (ie return "success"). The problem that I am having is that the method I am calling is already displaying a string (that is dynamic) in it's return type. As my method already displays a string, how do I configure this with JSF, so that I navigate to the appropriate page. The code below shows the problem more clearly.

xhtml file:

        <tr>
            <td><H2>Past Projects</H2>
            <h:dataTable value="#{projectBean.projectList}" var="p" border="1">

                <h:column>
                <f:facet name="header">
                Project Name
                </f:facet>
                #{p.projectName}
                <h:commandButton id="viewProject" action="#{projectBean.displayProjectDetails(p.project_id)}" value="View">
               </h:commandButton>
                </h:column>
            </h:dataTable>

            </td>
        </tr>

Java Class:

public String displayProjectDetails(int id) {
    factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
    EntityManager em = factory.createEntityManager();   

        em.getTransaction().begin();

        Query myQuery = em.createQuery("SELECT p FROM Projects p WHERE p.project_id=:projectId");
        myQuery.setParameter("projectId", id);
        List<Projects> currentProject=myQuery.getResultList();

        em.getTransaction().commit();
        em.close();

        String projectName=currentProject.get(0).getProjectName();
        String projectDescription=currentProject.get(0).getProjectDescription();

        String output=(projectName+"<br/>"+projectDescription+"<br/>");

        return output;

    } 

XML file:

//Faces file
 <navigation-case>
    <from-outcome>output</from-outcome>
    <to-view-id>/projectDescription.xhtml</to-view-id>
 </navigation-case>

Answer 1

To me this looks like some false design. You should use an action method which appropriately returns the navigation case string (or void if you want to stay on the page). The method should not return anything else. The other string should be returned from a getter, as appropriate.