JSP实现点击链接后下载文件(相当于右键另存)功能

/**
* 实现文件另存功能
*
* @param text
*            文件内容
* @param fileName
*            文件名称
* @return
*/
protected String renderFile(String text, String fileName)
throws IOException
{
response.addHeader("Content-Disposition", "attachment; filename="
+ fileName);
response.setContentType("application/octet-stream");
response.setCharacterEncoding("GB2312");
response.getWriter().write(text);
response.flushBuffer();
response.getWriter().close();
return null;
}

/**
* 提供下载的方法
* @return
*/
public String down()
{
String dir = getFullPath() + "/upload/file/";
try
{
if (!FileUtils.exists(dir))
{
new File(dir).mkdirs();
}
Random r = new Random(System.currentTimeMillis());
Integer randomInt = r.nextInt();
this.renderFile("test content:" + randomInt,randomInt + ".txt");
}
catch (IOException e)
{
e.printStackTrace();
this.renderText(e.getMessage());
}
return null;
}

<a href="${ctx}/va/va!down.do" >下载</a>