我试过这个：
- Java EE 7
- GlassFish 4.1.2
- PrimeFaces 6.2
- PrimeFaces-Extensions 6.2.9
在bean（类）代码处：
@ManagedBean
@ApplicationScoped
public class DocumentViewerController {
范围是@ApplicationScoped。我有一个私有的 StreamedContent 属性。以及两个主要的公共方法：
第一种方法：从p:commandButton的actionListener属性调用。该方法接收一个参数（在我的例子中）。
public void onPrerender(Tramite tramite) {
tramiteSelected = tramite;
numeroTramite = tramite.getNumero();
contrato = tramite.getContrato();
}
第二种方法：它是在对话框组件中的 pe:documentViewer 中使用的，如下所示：
<pe:documentViewer id="certificadoViewer"
height="500px"
width="750px"
cache="false"
value="#{documentViewerController.certificado}"
download="certificado_#{documentViewerController.numero}_#{documentViewerController.contrato}.pdf" />
注意：第二种方法就像一个属性（getter 和 setter）。这就是诀窍。
我项目的最终代码是：
# Bean (DocumentViewerController.java)：
package com.epmrpsd.certificado.consulta.controladores;
import com.epmrpsd.certificado.consulta.controladores.util.JsfUtil;
import com.epmrpsd.certificado.consulta.entidades.Tramite;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import javax.faces.bean.ApplicationScoped;
import javax.faces.bean.ManagedBean;
import org.primefaces.model.DefaultStreamedContent;
import org.primefaces.model.StreamedContent;
/**
*
* @author pbonilla
*/
@ManagedBean
@ApplicationScoped
public class DocumentViewerController {
private StreamedContent content;
private Integer numeroTramite;
private Integer contrato;
private Tramite tramiteSelected;
// Path where the file exists
private String pdfPathDirectory = "C:\\Users\\<user>\\certificados\\";
public void onPrerender(Tramite tramite) {
tramiteSelected = tramite;
numeroTramite = tramite.getNumero();
contrato = tramite.getContrato();
}
public StreamedContent getCertificado() {
InputStream stream = null;
try {
File file = new File(pdfPathDirectory + numeroTramite + "_" + contrato + ".pdf");
if (file.exists()) {
stream = new FileInputStream(file);
} else {
JsfUtil.addErrorMessage("Error", "No se ha encontrado el archivo");
}
this.content = new DefaultStreamedContent(stream, "application/pdf");
} catch (FileNotFoundException fnfex) {
JsfUtil.addErrorMessage("Error", "No se ha encontrado el archivo. Error: " + fnfex.getMessage());
fnfex.printStackTrace();
} catch (Exception e) {
JsfUtil.addErrorMessage("Error", "Se ha generado un error al cargar el certificado. Error: " + e.getMessage());
e.printStackTrace();
}
return content;
}
public void setCertificado(StreamedContent contenido) {
content = contenido;
}
public Tramite getTramiteSelected() {
return tramiteSelected;
}
public void setTramiteSelected(Tramite tramiteSelected) {
this.tramiteSelected = tramiteSelected;
}
public Integer getNumero() {
return numeroTramite;
}
public void setNumero(Integer numeroTramite) {
this.numeroTramite = numeroTramite;
}
public Integer getContrato() {
return contrato;
}
public void setContrato(Integer contrato) {
this.contrato = contrato;
}
}
#视图（index.xhtml）：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://xmlns.jcp.org/jsf/html"
xmlns:f="http://xmlns.jcp.org/jsf/core"
xmlns:p="http://primefaces.org/ui"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:pe="http://primefaces.org/ui/extensions">
<h:head>
<title>Consulta de Certificados Digitales</title>
<h:outputStylesheet library="css" name="epmrpsd.css" />
<h:outputStylesheet library="webjars" name="font-awesome/5.5.0/css/all-jsf.css" />
<h:outputStylesheet library="css" name="jsfcrud.css"/>
<h:outputScript library="js" name="jsfcrud.js"/>
<link rel="shortcut icon" type="image/png" href="#{resource['images/logo.png']}"/>
</h:head>
<h:body>
<div id="background" style="position: fixed;">
<h:form id="formCertificados">
<div class="ui-g" style="margin-top: 25px;">
<div class="ui-g-1"></div>
<div class="ui-g-10">
<p:growl id="mensajes" />
<Extra code> ...
<p:outputPanel id="pnlCertificado">
<p:dataTable id="tramitesTable"
value="#{tramiteController.items}"
var="tramite"
rowKey="#{tramite.id}"
selectionMode="single"
selection="#{tramiteController.selected}"
emptyMessage="No se encontraron trámites con los criterios dados"
rows="10"
rowsPerPageTemplate="10,20,30,40,50">
<p:column headerText="Número Trámite" >
<h:outputText value="#{tramite.numero}" />
</p:column>
<p:column headerText="Descripción" >
<h:outputText value="#{tramite.tipo.descripcion}" />
</p:column>
<p:column headerText="Número Contrato" >
<h:outputText value="#{tramite.contrato}" />
</p:column>
<p:column style="text-align: center" headerText="Acción" >
<center>
<p:commandButton id="viewCertificado"
styleClass="ui-priority-primary"
value="Ver certificado"
actionListener="#{documentViewerController.onPrerender(tramite)}"
update=":ViewCertificadoForm"
oncomplete="PF('ViewCertificadoDialog').show()" />
</center>
</p:column>
</p:dataTable>
</p:outputPanel>
</div>
<div class="ui-g-1"></div>
</div>
</h:form>
<ui:include src="ViewCertificado.xhtml"/>
</div>
</h:body>
</html>
视图的最后一个组件是（ViewCertificado.xhtml）：
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
xmlns:h="http://xmlns.jcp.org/jsf/html"
xmlns:f="http://xmlns.jcp.org/jsf/core"
xmlns:p="http://primefaces.org/ui"
xmlns:pe="http://primefaces.org/ui/extensions">
<ui:composition>
<p:dialog id="ViewCertificadoDlg"
widgetVar="ViewCertificadoDialog"
modal="true"
resizable="false"
appendTo="@(body)"
header="Certificado #{documentViewerController.contrato}">
<h:form id="ViewCertificadoForm">
<h:panelGroup id="display">
<p:panelGrid columns="1" rendered="#{documentViewerController.tramiteSelected != null}">
<pe:documentViewer id="certificadoViewer"
height="500px"
width="750px"
cache="false"
value="#{documentViewerController.certificado}"
download="certificado_#{documentViewerController.numero}_#{documentViewerController.contrato}.pdf" />
</p:panelGrid>
<p:commandButton value="Cerrar" onclick="ViewCertificadoDialog.hide()"/>
</h:panelGroup>
</h:form>
</p:dialog>
</ui:composition>
</html>