文件下载工具类

有些文件下载会直接下载，当有些文件是pdf，txt之类的文件，可以支持在线打开。或者直接使用方法openOnlineDownload也可实现能在线打开的打开，不能打开的直接下载。

public class DownloadUtil {
/**
 * 下载文件，需要返回的response，文件名，文件路径
 * @param filename 文件名，会做中文乱码处理
 * @param path 文件路径
 * @param response
 */
public static HttpServletResponse downloadFile(String filename, String path,HttpServletResponse response) {
try {
            File file = new File(path);
// 以流的形式下载文件。
            InputStream fis = new BufferedInputStream(new FileInputStream(path));
byte[] buffer = new byte[fis.available()];
            fis.read(buffer);
            fis.close();
// 清空response
            response.reset();
// 设置response的Header
            response.addHeader("Content-Disposition", "attachment;filename="+new String(filename.getBytes(), "ISO-8859-1") );
            response.addHeader("Content-Length", "" + file.length());
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            response.setContentType("application/octet-stream");
            toClient.write(buffer);
            toClient.flush();
            toClient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
return response;
    }
/**
 * 下载支持在线打开
 * @param filePath
 * @param response
 * @param isOnLine
 * @throws Exception
 */
public static HttpServletResponse openOnlineDownload(String filename,String path, HttpServletResponse response, boolean isOnLine) throws Exception {
        File file = new File(path);
if (!file.exists()) {
          response.sendError(404, "File not found!");
        }
        BufferedInputStream br = new BufferedInputStream(new FileInputStream(file));
byte[] buf = new byte[1024];
int len = 0;

        response.reset(); // 非常重要
if (isOnLine) { // 在线打开方式
          URL u = new URL("file:///" + path);
          response.setContentType(u.openConnection().getContentType());
          response.setHeader("Content-Disposition", "inline; filename=" + new String(filename.getBytes(), "ISO-8859-1"));
// 文件名应该编码成UTF-8
        }
        OutputStream out = response.getOutputStream();
while ((len = br.read(buf)) > 0)
          out.write(buf, 0, len);
        br.close();
        out.close();
return response;
      }
}