今天在pdf和excel中都实现了在浏览器弹出下载框

将之前在网上查找的生成excel表格代码稍微修改下：

public class CreateSimpleExcelToDisk {
 /**
  * @功能：手工构建一个简单格式的Excel
  */
 private static List<News> getNews() throws Exception
 {
  List<News> data = http://www.mamicode.com/new ArrayList();>
用servlet实现下载：此代码可以套用
public class ExpExcelServlet extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String fileName = "news.et";
		response.setContentType("octets/stream");
		response.addHeader("Content-Disposition", "attachment;filename="
				+ URLEncoder.encode(fileName, "utf-8"));
		

		try {
			NewsDao dao = new NewsDao();
			ArrayList<News> list = dao.queryAll();
			CreateSimpleExcelToDisk ce=new CreateSimpleExcelToDisk();
					OutputStream out = response.getOutputStream();
				ce.ExpExcel(out);
				out.close();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			System.out.println("et导出成功！");
		} 

	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request,response);
	}

}

网上的资料

可以采用：
1、RequestDispatcher的方式进行；
2、采用文件流输出的方式下载。

1、采用RequestDispatcher的方式进行
            jsp页面中添加如下代码：
           <%
      response.setContentType("application/x-download");//设置为下载application/x-download
      String filedownload = "/要下载的文件名";//即将下载的文件的相对路径
      String filedisplay = "最终要显示给用户的保存文件名";//下载文件时显示的文件保存名称
      filenamedisplay = URLEncoder.encode(filedisplay,"UTF-8");
      response.addHeader("Content-Disposition","attachment;filename=" + filedisplay);
    
      try
      {
          RequestDispatcher dis = application.getRequestDispatcher(filedownload);
          if(dis!= null)
          {
              dis.forward(request,response);
          }
          response.flushBuffer();
      }
      catch(Exception e)
      {
          e.printStackTrace();
      }
      finally
      {
    
      }
%>
2、采用文件流输出的方式下载
         <%@page language="java" contentType="application/x-msdownload"    pageEncoding="gb2312"%><%
      //关于文件下载时采用文件流输出的方式处理：
      //加上response.reset()，并且所有的％>后面不要换行，包括最后一个；
      response.reset();//可以加也可以不加
      response.setContentType("application/x-download");
      String filedownload = "想办法找到要提供下载的文件的物理路径＋文件名";
      String filedisplay = "给用户提供的下载文件名";
      filedisplay = URLEncoder.encode(filedisplay,"UTF-8");
      response.addHeader("Content-Disposition","attachment;filename=" + filedisplay);
      OutputStream outp = null;
      FileInputStream in = null;
      try
      {
          outp = response.getOutputStream();
          in = new FileInputStream(filenamedownload);
          byte[] b = new byte[1024];
          int i = 0;
          while((i = in.read(b)) > 0)
          {
              outp.write(b, 0, i);
          }
          outp.flush();
      }
      catch(Exception e)
      {
          System.out.println("Error!");
          e.printStackTrace();
      }
      finally
      {
          if(in != null)
          {
              in.close();
              in = null;
          }
          if(outp != null)
          {
              outp.close();
              outp = null;
          }
      }
%>
在wsad里面写JSP文件下载,总是出现这个异常,getOutputStream() has already been called for this response,输出流已经被调用了.
      上网查半天终于明白一点,JSP早下载文件的时候用到了OutputStream,而在Application Server在处理编译jsp时对于％>和<％之间的内容一般是原样输出，而且默认是PrintWriter.