以流的方式下载附件

<a onclick="downloadFile(filePath)" href="#">(下载)</a>
<iframe name="hidden_frame" id="hidden_frame" style="display:none"></iframe>

function downloadFile(filePath){
    var fileName=encodeURI(filePath);
    document.getElementById("hidden_frame").src = "JS/StreetMap/downloadFile.jsp?fileName="+fileName;
}

public void downloadFile() {
		HttpServletResponse response = ServletActionContext.getResponse();
		HttpServletRequest request = getRequest();
		response.setCharacterEncoding("GBK");
		String fileUrl=request.getParameter("fileUrl");
		String fileName=request.getParameter("fileName");
		String cmsAttachRealFile = "";
		try {
			fileUrl = new String(fileUrl.getBytes("ISO8859-1"),"GBK");		
		cmsAttachRealFile = FilePathSptUtil.UPLOAD_ROOT_PATH
		//+ FilePathSptUtil.UPLOAD_CMS
		+ fileUrl;
		fileName = new String(fileName.getBytes("ISO8859-1"),"UTF-8"); 
		fileName = URLEncoder.encode(fileName, "UTF-8");
		} catch (Exception e1) {
			// TODO 附件流下载  弹出下载框
			e1.printStackTrace();
		}
		try {
			OutputStream o = response.getOutputStream();
			byte b[] = new byte[500];
			File fileLoad = new File(cmsAttachRealFile);
			response.setContentType("application/octet-stream");
			response.setHeader("content-disposition",
					"attachment; filename=\""
					+ fileName + "\"");
			long fileLength = fileLoad.length();
			String length1 = String.valueOf(fileLength);
			response.setHeader("Content_Length", length1);
			FileInputStream in = new FileInputStream(fileLoad);
			int n;
			while ((n = in.read(b)) != -1) {
				o.write(b, 0, n);
			}
			in.close();
			o.close();
		} catch (Exception e) {
			// TODO: handle exception
		}
	}



//jsp
response.setCharacterEncoding("UTF-8");
    String fileName=request.getParameter("fileName");
    String applicationPath = application.getRealPath("");
    String filePath =applicationPath;
    String suffixName = fileName.substring(fileName.lastIndexOf(".")+1,fileName.length()).toLowerCase();
    String realFilePath = "";
    try {
//        fileName = new String(fileName.getBytes("ISO-8859-1"),"UTF-8");
        realFilePath = filePath+fileName;//附件地址
        File fileLoad = new File(realFilePath);
        if(!fileLoad.exists()){
            System.out.println("没有您要打开的文件");
        }else {
//            fileName = URLEncoder.encode(fileName, "UTF-8");
            String realFileName = fileName.substring(fileName.lastIndexOf("/")+1,fileName.length());
            realFileName = URLEncoder.encode(realFileName, "UTF-8");
            OutputStream o = response.getOutputStream();
            byte b[] = new byte[512];
            //contentType设定
            String contentType = ZipUtil.getContentType(suffixName);
            response.setContentType(contentType);
            response.setContentType("application/octet-stream");
            //attachment表示网页会出现保存、打开对话框;inline 直接页面打开
            response.setHeader("content-disposition","attachment; filename=\"" + realFileName + "\"");
            //response.setHeader("content-disposition","inline; filename=\"" + fileName + "\"");
            long fileLength = fileLoad.length();
            String length1 = String.valueOf(fileLength);
            response.setHeader("Content_Length", length1);
            FileInputStream in = new FileInputStream(fileLoad);
            int n;
            while ((n = in.read(b)) != -1) {
                o.write(b, 0, n);
            }
            in.close();
            o.close();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }