Primefaces 中upload 怎么不显示呢
java
package com.mytest;

import org.primefaces.model.UploadedFile;

import javax.faces.application.FacesMessage;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import javax.faces.context.FacesContext;

/**
 * Created with IntelliJ IDEA.
 * User: Administrator
 * Date: 13-4-17
 * Time: 下午3:57
 * To change this template use File | Settings | File Templates.
 */

@ManagedBean
@RequestScoped
public class FileUploadBean {
    private UploadedFile file;

    public UploadedFile getFile() {
        return file;
    }

    public void setFile(UploadedFile file) {
        this.file = file;
    }

    public void upload() {
        FacesMessage msg = new FacesMessage("Successful", file.getFileName() + " is uploaded.");
        FacesContext.getCurrentInstance().addMessage(null, msg);
    }

}

xhtml

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
                xmlns:ui="http://java.sun.com/jsf/facelets"
                xmlns:h="http://java.sun.com/jsf/html"
                xmlns:p="http://primefaces.org/ui"
                template="../templates/ui.xhtml">

    <ui:define name="content">
        <div class="entry">
            <h3 >This upload </h3>
            <h:form enctype="multipart/form-data">

                <p:messages showDetail="true"/>
                <p:fileUpload value="#{fileUploadBean.file}"   mode="simple"/>
                <br/><br/>
                <p:commandButton value="Submit" ajax="false" actionListener="#{fileUploadBean.upload}"/>

            </h:form>
        </div>
    </ui:define>
</ui:composition>
xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"