response.setContentType()的String参数及对应类型
内容来自：http://topic.csdn.net/u/20071203/13/f8264802-1936-4773-b109-50c35f2d0ba7.html里的"marsseeker"。
<option value="image/bmp">BMP</option> <option value="image/gif">GIF</option> <option value="image/jpeg">JPEG</option> <option value="image/tiff">TIFF</option> <option value="image/x-dcx">DCX</option> <option value="image/x-pcx">PCX</option> <option value="text/html">HTML</option> <option value="text/plain">TXT</option> <option value="text/xml">XML</option> <option value="application/afp">AFP</option> <option value="application/pdf">PDF</option> <option value="application/rtf">RTF</option> <option value="application/msword">MSWORD</option> <option value="application/vnd.ms-excel">MSEXCEL</option> <option value="application/vnd.ms-powerpoint">MSPOWERPOINT</option> <option value="application/wordperfect5.1">WORDPERFECT</option> <option value="application/vnd.lotus-wordpro">WORDPRO</option> <option value="application/vnd.visio">VISIO</option> <option value="application/vnd.framemaker">FRAMEMAKER</option> <option value="application/vnd.lotus-1-2-3">LOTUS123</option><option value="application/octet-stream">信息流</option>
