//xml

                Document document=DocumentHelper.createDocument();

                Element root=document.addElement("root");

//。。。。。省略document的过程。。。。。

//下载到指定目录

OutputFormat format=OutputFormat.createPrettyPrint();

                format.setEncoding("UTF-8");

                XMLWriter writer=new XMLWriter(new FileOutputStream(new File("D://dzoa.xml")),format);

                writer.write(document);

                writer.close();

//下载到客户端

DownloadTool.doReady(response, "application/octet-stream", 0, "dzoa.xml");

                XMLWriter writer=new XMLWriter(response.getOutputStream(), OutputFormat.createPrettyPrint());

                writer.write(document);

　　　　　　　　　writer.close();

//相关方法代码

  /**

     * @param mimeType 文件的mime-type，如为null或空字符串，就取multipart/form-data

     * @param filelen  文件长度，大于0表示真实长度，0或负值表示unknown

     * @param fileName 文件名称

     * @param inline   可选项，是inline还是attachment，默认false

     */

    public static void doReady(HttpServletResponse response, String mimeType, long filelen, String fileName, boolean... inline) {

        if (mimeType == null || mimeType.isEmpty()) mimeType = "multipart/form-data";

        fileName = rawEncode(fileName); // RFC 3986

        response.setCharacterEncoding("UTF-8");

        response.setContentType(mimeType);

        if (filelen > 0) response.setHeader("Content-Length", String.valueOf(filelen));

        // firefox: filename*=utf-8''

        // IE or chrome: filename= or filename*=utf-8''

        // Xunlei: filename= or filename*=utf-8''

        response.setHeader("Content-Disposition", ((inline.length > 0 && inline[0]) ? "inline" : "attachment") + "; filename=\"" + fileName + "\"" + "; filename*=utf-8''" + fileName);

    }

------------------------------------一般情况的下载附件可调用下列方法-------------------------

   /**

     * @param mimeType 文件的mime-type，如为null或空字符串，就取multipart/form-data

     * @param data     数据

     * @param fileName 文件名称

     * @param inline   可选项，是inline还是attachment，默认false

     */

    public static void download(HttpServletResponse response, String mimeType, byte[] data, String fileName, boolean... inline) {

        response.reset();

        doReady(response, mimeType, (long) data.length, fileName, inline);

        OutputStream os = null;

        try {

            os = response.getOutputStream();

            os.write(data);

            os.flush();

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            close(os);

        }

    }

-----------------------------------如果客户端还是没有出来附件下载，检查一下代码---------------------------------------

 //数据导出

     function gwExport(){

         top.$.fn._confirm("确认要导出数据吗？", function(i){

             if(1 == i){

                 var cVal = "";

                 var cValStr=[];

                 $("#myTable td input[name=fileCheck]").each(function(){

                     if(this.checked){

                        cValStr.push($(this).val());

                     }

                 });

                 cVal=cValStr.join(",");

                 if(cVal==""){

                     top.$.fn._alert("请选择需要导出的公文。");

                     return;

                 }

                 //alert(cVal);

                 location.href = "${ctx}/oa/myflow/procinst/gwExport?" + $.param({"pInsIds": cVal});

                 /* $.post("${ctx}/oa/myflow/procinst/gwExport", {"pInsIds": cVal}, function(data){

                     top.$.fn._alert(data.info);

                     if(data.state==1){

                        // location.reload();

                     }

                 }); */

             }

         });

     }