Jsf中实现文件的下载注意的问题

1、关于jsf文件的的下载，其实现类很简单，关键是应用需要注意的问题很多，下面是文件下载的通用类

package com.cvicse.report.ui.viewer.jsf.template;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import javax.faces.context.FacesContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;

/**
 * @author gao_jie 
 * 
 * jsf文件下载操作
 */
public class FileDownLoad {

	/**
	 * 下载文件
	 * @param path
	 * @param fileName
	 */
	public static void downloadFile(String path, String fileName) {
		try {
			// 获得ServletContext对象
			ServletContext servletContext = (ServletContext) FacesContext
					.getCurrentInstance().getExternalContext().getContext();
			// 取得文件的绝对路径
			String realName = servletContext.getRealPath(path) + File.separator
					+ fileName;
			HttpServletResponse response = (HttpServletResponse) FacesContext
					.getCurrentInstance().getExternalContext().getResponse();
			downloadFile(response, realName, fileName);
		} catch (IOException e) {
			e.printStackTrace();
		}
		FacesContext.getCurrentInstance().responseComplete();
	}

	/**
	 * 下载文件
	 * @param response
	 * @param realName
	 * @param fileName
	 * @throws IOException
	 */
	public static void downloadFile(HttpServletResponse response,
			String realName, String fileName) throws IOException {
		fileName = java.net.URLEncoder.encode(fileName, "UTF-8");
		response.setHeader("Content-Disposition", "attachment; filename=\""
				+ fileName + "\"");
		response.setContentType("application/x-msdownload;charset=UTF-8");
		ServletOutputStream servletOutputStream = response.getOutputStream();
		byte[] b = new byte[1024];
		int i = 0;
		FileInputStream fis = new java.io.FileInputStream(realName);
		while ((i = fis.read(b)) > 0) {
			servletOutputStream.write(b, 0, i);
		}
		servletOutputStream.flush();
		servletOutputStream.close();
	}
/**
  * 下载文件到本地
  */
 public void downLoadFileForLocal(String content,String fileName) {
  try {
   HttpServletResponse response = (HttpServletResponse) FacesContext
     .getCurrentInstance().getExternalContext().getResponse();
   String fileName = java.net.URLEncoder
     .encode(fileName, "UTF-8");
   response.setHeader("Content-Disposition", "attachment; filename=\""
     + fileName + "\"");
   response.setContentType("application/x-msdownload;charset=UTF-8");
   ServletOutputStream servletOutputStream = response
     .getOutputStream();
   servletOutputStream.write(content.getBytes());
   servletOutputStream.flush();
   servletOutputStream.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
  FacesContext.getCurrentInstance().responseComplete();
 }

}

 

2、应用该类下载时注意

使用方法 

1、在bean的方法中调用函数1即可。如abean中download方法调用了该方法，前台可以这样调用： 

<h:commandButton value="download" action="#{aBean.download}"></h:commandButton> 

或者 

<h:commandLink value="download" action="#{fileUploadForm.download}"></h:commandLink> 

注意：一定不要用richfaces的ajax中的a4j:commandLink和a4j:commandButton，因为使用原生AJAX之后就会导致文件在页面上生成。
f:view将按钮包裹，注意不要给view添加renderKitId="AJAX"。

2、jsp页面可以这样调用： 

<%@ page contentType="text/html; charset=gb2312"%><%@page import="java.io.*"%><%
    String filename = "";
if (request.getParameter("filename") != null) {
        filename =     request.getParameter("filename");
    }
try {
        FileDownLoad.downloadFile(response,getServletContext().getRealPath(filename),filename);
        } catch(final IOException e) {
            System.out.println ( "出现IOException." + e );
          } catch(final IllegalStateException e) {
            System.out.println ( "出现IllegalStateException." + e );
        }  
%> 

于是jsf页面我们可以借助outputlink来调用该页面 

<h:outputLink id="downloadfile"    value="#{page/FileDownload.jsp?filename=}">
<t:outputText value="下载文件" />
</h:outputLink>