「软帝学院」：Java下载文件的几种方式

欢迎大家来到IT世界,在知识的湖畔探索吧!

1.以流的方式下载.

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;

}

2.下载本地文件

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();

}

}

3.下载网络文件

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();

}

}

4.支持在线打开的方式

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();

}

最后，开发这么多年我也总结了一套学习Java的资料，如果你在技术上面想提升自己的话，可以关注我，私信发送领取资料或者在评论区留下自己的联系方式，有时间记得帮我点下转发让跟多的人看到哦