Lazy loading is not implemented

HTTP Status 500 - Lazy loading is not implemented.

type Exception report

message Lazy loading is not implemented.

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Lazy loading is not implemented.
    javax.faces.webapp.FacesServlet.service(FacesServlet.java:671)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
root cause

java.lang.UnsupportedOperationException: Lazy loading is not implemented.
    org.primefaces.model.LazyDataModel.load(LazyDataModel.java:112)
    org.primefaces.component.datatable.DataTable.loadLazyData(DataTable.java:1024)
    org.primefaces.component.datatable.DataTableRenderer.preRender(DataTableRenderer.java:97)
    org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:85)
    javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:920)
    javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
    javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
    javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:890)
    javax.faces.component.UIComponent.encodeAll(UIComponent.java:1856)
    javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:458)
    com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:134)
    com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
    com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
    javax.faces.webapp.FacesServlet.service(FacesServlet.java:659)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
note The full stack trace of the root cause is available in the Apache Tomcat/9.0.0.M15 logs.

Trecho de livro.xhtml:

            <h:form id="formTabelaLivros">
                <p:dataTable value="#{livroBean.livroDataModel}" var="livro" id="tabelaLivros" paginator="true" rows="5" lazy="true" sortMode="multiple">
                    <f:facet name="header">Livros cadastrados</f:facet>
                    <p:column headerText="Título" sortBy="#{livro.titulo}"  filterBy="#{livro.titulo}" filterMatchMode="startsWith">
                        <h:outputText value="#{livro.titulo}" />
                    </p:column>
                    <p:column headerText="ISBN" sortBy="#{livro.isbn}" filterBy="#{livro.isbn}" filterMatchMode="contains">
                        <h:outputText value="#{livro.isbn}" />
                    </p:column>
                    <p:column headerText="Preço" sortBy="#{livro.preco}" filterBy="#{livro.preco}" filterFunction="#{livroBean.precoEhMenor}">
                        <h:outputText value="#{livro.preco}">
                            <f:convertNumber type="currency" pattern="R$ #0.00"
                                currencySymbol="R$" locale="pt_BR" />
                        </h:outputText>
                    </p:column>
                    <p:column headerText="Data" sortBy="#{livro.dataLancamento.time}" filterBy="#{livro.dataLancamento.time}" filterMatchMode="contains">
                        <h:outputText value="#{livro.dataLancamento.time}">
                            <f:convertDateTime pattern="dd/MM/yyyy"
                                timeZone="America/Sao_Paulo" />
                        </h:outputText>
                    </p:column>
                    <p:column headerText="Alterar">
                        <h:commandLink value="Alterar" action="#{livroBean.carregar(livro)}"/>
                    </p:column>
                    <p:column headerText="Remover">
                        <h:commandLink value="Remover" action="#{livroBean.remover(livro)}"/>
                    </p:column>
                </p:dataTable>
            </h:form>

Classe livroDataModel:

public class LivroDataModel extends LazyDataModel<Livro>{

    private static final long serialVersionUID = 1L;
    private DAO<Livro> dao = new DAO<Livro>(Livro.class);

    public LivroDataModel() {
        super.setRowCount(dao.quantidadeDeElementos());
    }

    public List<Livro> load(int inicio, int quantidade, String campoOrdenacao, SortOrder sentidoOrdenacao, Map<String, Object> filtros) {
        String titulo = (String) filtros.get("titulo");
        return dao.listaTodosPaginada(inicio, quantidade, "titulo", titulo);
    }
}

Métodos acrescentados ao DAO:

    public List<T> listaTodosPaginada(int firstResult, int maxResults, String coluna, String valor) {
        EntityManager em = new JPAUtil().getEntityManager();
        CriteriaQuery<T> query = em.getCriteriaBuilder().createQuery(classe);
        Root<T> root = query.from(classe);

        if(valor != null)
            query = query.where(em.getCriteriaBuilder().like(root.<String>get(coluna), valor + "%"));

        List<T> lista = em.createQuery(query).setFirstResult(firstResult).setMaxResults(maxResults).getResultList();

        em.close();
        return lista;
    }

    public int quantidadeDeElementos() {
        EntityManager em = new JPAUtil().getEntityManager();
        long result = (Long) em.createQuery("select count(n) from " + classe.getSimpleName() + " n")
                .getSingleResult();
        em.close();

        return (int) result;
    }