HTML require string or number values to populate forms. In our case, the property publisher of the Book class is an object reference. JSF allows the mapping from object and string and back by using face converters, which are classes annotated with @FacesConverter and implementing the javax.faces.convert.Converter interface:

@FacesConverter( value="pl.model.converter.PublisherConverter")
public class PublisherConverter implements Converter {
  @Override
  public Object getAsObject( FacesContext context, 
      UIComponent component, String value) {
    PublisherController ac = FacesContext
        .getCurrentInstance()
        .getApplication()
        .evaluateExpressionGet( context, "#{publisherCtrl}",
            PublisherController.class);
    EntityManager em = ac.getEntityManager();
    if (value == null) return null;
    else return em.find( Publisher.class, value);
  }
  @Override
  public String getAsString( FacesContext context, 
      UIComponent component, Object value) {
    if (value == null) return null;
    else if (value instanceof Publisher) {
      return ((Publisher) value).getName();
    }
    else return null;
  }
}

It defines two methods, getAsObject and getAsString, responsible for the two mappings. It allows to define custom representations which can be used not only in connection with HTML forms but also allows serialization which can be used with display views. For being able to extract an object from database we need an EntityManager which can be obtained from our controller class instances (e.g., the managed bean publisherCtrl). The instance of the controller can be obtained by using the FacesContext singletone as shown above:

PublisherController ac = FacesContext.getCurrentInstance()
     .getApplication()
     .evaluateExpressionGet( context, "#{publisherCtrl}", 
          PublisherController.class);

In addition, we need to add a getEntityManager method in the controller class as follows:

@ManagedBean( name="publisherCtrl")
@SessionScoped
public class PublisherController {
  @PersistenceContext( unitName="UnidirAssocApp")
  private EntityManager em;
  @Resource()
  UserTransaction ut;

  public EntityManager getEntityManager() {
    return this.em;
  }
  ...
}

JSF needs to compare two publisher instances, when the publisher list has to auto-select the current publisher, in the update book use case. For this reason, the Publisher model class needs to implement the equals method. In our case, two publishers are "one and the same", if the values of their name property are equal:

@Override
public boolean equals( Object obj) {
  if (obj instanceof Publisher) {
    Publisher publisher = (Publisher) obj;
    return ( this.name.equals( publisher.name));
  } else return false;
}

To allow selection of objects which have to be associated with the currently edited object from a list in the create and update use cases, an HTML selection list (a select element) is populated with the instances of the associated object type with the help of JSF h:selectOneMenu element. The WebContent/views/books/create.xhtml file is updated as follows:

<ui:composition template="/WEB-INF/templates/page.xhtml">
 <ui:define name="content">
  <h:form id="createBookForm" styleClass="pure-form pure-form-aligned">
   <h:panelGrid columns="3">
    ...
    <h:outputLabel for="publisher" value="Publisher:" />
    <h:selectOneMenu id="publisher" value="#{book.publisher}">
     <f:selectItem itemValue="" itemLabel="---" />
     <f:selectItems value="#{publisherCtrl.publishers}" var="p" 
                    itemLabel="#{p.name}" itemValue="#{p}" />
     <f:converter converterId="pl.model.converter.PublisherConverter" />
    </h:selectOneMenu>
    <h:message for="publisher" errorClass="error" />
    </h:panelGrid>
     <h:commandButton value="Create" 
         action="#{bookCtrl.add( book.isbn, book.title, 
         book.year, book.publisher.name)}" />
  </h:form>
 </ui:define>
</ui:composition>

The object-to-string and back converter is specified by using the f:converter JSF element and its associated @converterId attribute. The value of this attribute must be the same with the one specified by the value property of the annotation @FacesConverter used when the converter class is defined, e.g., @FacesConverter( value="pl.model.converter.PublisherConverter"). In general, the converter simple class name should be used (e.g., PublisherConverter), or the complete fully qualified name, if there is a risk of naming conflicts (e.g., pl.model.converter.PublisherConverter). We recommend to use the fully qualified name in all cases.

The #{publisherCtrl.publishers} JSF expression results in calling the getPublishers method of the PublisherController class, which is responsible to return the list of available publishers:

public List<Publisher> getPublishers() {
  return Publisher.getAllObjectsAll( em);
}

The creation of the book is obtained by using the h:commandButton JSF element. It results in the invocation of the add method of the BookController class:

public String add( String isbn, String title, Integer year, 
    Publisher publisher) {
  try {
    Book.add( em, ut, isbn, title, year, publisher);
    // Enforce clearing the form after creating the Book row.
    // Without this, the form will show the latest completed data
    FacesContext facesContext = FacesContext.getCurrentInstance();
    facesContext.getExternalContext().getRequestMap().remove( "book");
  } catch ( EntityExistsException e) {
    try {
      ut.rollback();
    } catch ( Exception e1) {
      e1.printStackTrace();
    }
    e.printStackTrace();
  } catch ( Exception e) {
    e.printStackTrace();
  }
  return "create";
}

It simply calls the Book.add method, responsible with the creation of a new row in the books table.

The code for the update book use case is very similar, the only important modification being the addition of the select element (i.e., using the h:selectOneMenu JSF element), which allows to select which book to update:

<ui:composition template="/WEB-INF/templates/page.xhtml">
 <ui:define name="content">
  <h:form id="createBookForm" styleClass="pure-form pure-form-aligned">
   <h:panelGrid columns="3">
    ...
    <h:outputLabel for="selectBook" value="Select book: " />
    <h:selectOneMenu id="selectBook" value="#{book.isbn}">
     <f:selectItem itemValue="" itemLabel="---" /> 
     <f:selectItems value="#{bookCtrl.books}" var="b" 
         itemValue="#{b.isbn}" itemLabel="#{b.title}" /> 
     <f:ajax listener="#{bookCtrl.refreshObject( book)}" 
         render="isbn title year publisher"/>
    </h:selectOneMenu>
    <h:message for="selectedBook"/>
     ...
   </h:panelGrid>
   <h:commandButton value="Create" action="#{bookCtrl.add( 
       book.isbn, book.title, book.year, book.publisher.name)}" />
  </h:form>
 </ui:define>
</ui:composition>