Servlet 在线打开Excel,pdf,word......

网上好多资料都说可以通过
  ServletOutputStream out = res.getOutputStream();
并且设置
// MIME type for pdf doc
    response.setContentType( "application/pdf" ); 
或
  // MIME type for MSWord doc
    response.setContentType( "application/msword" );
或
    response.setContentType("application/vnd.ms-excel");

response.setHeader("Content-Disposition", "inline; filename=\"" + filename + "\"");
我的代码如下
public class MyServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
                ServletContext context = getServletConfig().getServletContext();
//测试文件test.xls ,text.doc
File f = new File("D:\\test.pdf");
String filename = f.getName();
int length = 0;
ServletOutputStream op = response.getOutputStream();
response.setContentLength((int) f.length());

                //response.setContentType( "application/msword" );
               // response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-type","application/pdf");

response.setHeader("Content-Disposition", "inline; filename=\"" + filename + "\"");
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "No-cache");
response.setDateHeader("Expires", 0);

byte[] bytes = new byte[1024];
DataInputStream in = new DataInputStream(new FileInputStream(f));
while ((in != null) && ((length = in.read(bytes)) != -1)) {
    op.write(bytes, 0, length);
}
op.close();
response.flushBuffer();
        }
}