详解Java文件下载的几种实现方式

java文件下载的几种方式，具体如下:

public httpservletresponse download(string path, httpservletresponse response) {
    try {
      // path是指欲下载的文件的路径。
      file file = new file(path);
      // 取得文件名。
      string filename = file.getname();
      // 取得文件的后缀名。
      string ext = filename.substring(filename.lastindexof(".") + 1).touppercase();

      // 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()));
      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 ex) {
      ex.printstacktrace();
    }
    return response;
  }

  public void downloadlocal(httpservletresponse response) throws filenotfoundexception {
    // 下载本地文件
    string filename = "operator.doc".tostring(); // 文件的默认保存名
    // 读到流中
    inputstream instream = new fileinputstream("c:/operator.doc");// 文件的存放路径
    // 设置输出的格式
    response.reset();
    response.setcontenttype("bin");
    response.addheader("content-disposition", "attachment; filename=\"" + filename + "\"");
    // 循环取出流中的数据
    byte[] b = new byte[100];
    int len;
    try {
      while ((len = instream.read(b)) > 0)
        response.getoutputstream().write(b, 0, len);
      instream.close();
    } catch (ioexception e) {
      e.printstacktrace();
    }
  }

  public void downloadnet(httpservletresponse response) throws malformedurlexception {
    // 下载网络文件
    int bytesum = 0;
    int byteread = 0;

    url url = new url("windine.blogdriver.com/logo.gif");

    try {
      urlconnection conn = url.openconnection();
      inputstream instream = conn.getinputstream();
      fileoutputstream fs = new fileoutputstream("c:/abc.gif");

      byte[] buffer = new byte[1204];
      int length;
      while ((byteread = instream.read(buffer)) != -1) {
        bytesum += byteread;
        system.out.println(bytesum);
        fs.write(buffer, 0, byteread);
      }
    } catch (filenotfoundexception e) {
      e.printstacktrace();
    } catch (ioexception e) {
      e.printstacktrace();
    }
  }

 //支持在线打开文件的一种方式

public void download(string filepath, httpservletresponse response, boolean isonline) throws exception {
    file f = new file(filepath);
    if (!f.exists()) {
      response.senderror(404, "file not found!");
      return;
    }
    bufferedinputstream br = new bufferedinputstream(new fileinputstream(f));
    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:///" + filepath);
      response.setcontenttype(u.openconnection().getcontenttype());
      response.setheader("content-disposition", "inline; filename=" + f.getname());
      // 文件名应该编码成utf-8
    } else { // 纯下载方式
      response.setcontenttype("application/x-msdownload");
      response.setheader("content-disposition", "attachment; filename=" + f.getname());
    }
    outputstream out = response.getoutputstream();
    while ((len = br.read(buf)) > 0)
      out.write(buf, 0, len);
    br.close();
    out.close();
  }

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