SpringBoot implements multiple ways to download files

16361840:

1. Read the file into the memory at one time in the form of a stream, and output it to the front end through the response output stream

/**
* @param path 想要下载的文件的路径
* @param response
* @功能描述 下载文件:
*/
@RequestMapping("/download")
public void download(String path, HttpServletResponse response) {
    
    
try {
    
    
// path是指想要下载的文件的路径
File file = new File(path);
log.info(file.getPath());
// 获取文件名
String filename = file.getName();
// 获取文件后缀名
String ext = filename.substring(filename.lastIndexOf(".") + 1).toLowerCase();
log.info("文件后缀名：" + ext);
 
// 将文件写入输入流
FileInputStream fileInputStream = new FileInputStream(file);
InputStream fis = new BufferedInputStream(fileInputStream);
byte[] buffer = new byte[fis.available()];
fis.read(buffer);
fis.close();
 
// 清空response
response.reset();
// 设置response的Header
response.setCharacterEncoding("UTF-8");
//Content-Disposition的作用：告知浏览器以何种方式显示响应返回的文件，用浏览器打开还是以附件的形式下载到本地保存
//attachment表示以附件方式下载 inline表示在线打开 "Content-Disposition: inline; filename=文件名.mp3"
// filename表示文件的默认名称，因为网络传输只支持URL编码的相关支付，因此需要将文件名URL编码后进行传输,前端收到后需要反编码才能获取到真正的名称
response.addHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));
// 告知浏览器文件的大小
response.addHeader("Content-Length", "" + file.length());
OutputStream outputStream = new BufferedOutputStream(response.getOutputStream());
response.setContentType("application/octet-stream");
outputStream.write(buffer);
outputStream.flush();
} catch (IOException ex) {
    
    
ex.printStackTrace();
	}
} 

1.1 Download files

@RequestMapping("getFile")
@ResponseBody
public void getFile(HttpServletResponse response) throws Exception{
    
    
    File readFile = new File("/home/ssx/Music/CloudMusic/夜曲-周杰伦.flac");
    //字节流-用于读文件  这里只是demo用的非缓冲流。实际项目可以用BufferedInputStream。 此功能是读取图片，所以用的字节流。如果是文本的话可以用字符流效率高，具体类看下面注释
	//        BufferedReader bufferedReader = new BufferedReader(new FileReader(readFile));//字符流
    FileInputStream fileInputStream = new FileInputStream(readFile);//字节流
    //设置文件下载方式
    response.setHeader("content-disposition","attachment;filename="+ URLEncoder.encode("夜曲-周杰伦.flac","utf-8"));
    //获取servlet响应输出字节流
	//        PrintWriter writer = response.getWriter();//字符流
    ServletOutputStream outputStream = response.getOutputStream(); //字节流

    //流数据交换，每次交换10k数据大小 （1024k = 1m）
    byte[] bytes = new byte[1024*10];
    int read;
    do {
    
    
        read = fileInputStream.read(bytes);
        outputStream.write(bytes,0,read);
    }while (-1 != read);

    //关闭资源
    IOUtils.closeQuietly(fileInputStream);
    IOUtils.closeQuietly(outputStream);
}

2. Write the data in the input stream to the response output stream cyclically, instead of reading it to the memory at one time, and output it to the front end through the response output stream

/**
* @param path 指想要下载的文件的路径
* @param response
* @功能描述 下载文件:将输入流中的数据循环写入到响应输出流中，而不是一次性读取到内存
*/
@RequestMapping("/downloadLocal")
public void downloadLocal(String path, HttpServletResponse response) throws IOException {
    
    
// 读到流中
InputStream inputStream = new FileInputStream(path);// 文件的存放路径
response.reset();
response.setContentType("application/octet-stream");
String filename = new File(path).getName();
response.addHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(filename, "UTF-8"));
ServletOutputStream outputStream = response.getOutputStream();
byte[] b = new byte[1024];
int len;
//从输入流中读取一定数量的字节，并将其存储在缓冲区字节数组中，读到末尾返回-1
while ((len = inputStream.read(b)) > 0) {
    
    
outputStream.write(b, 0, len);
}
inputStream.close();
} 

3. Download the network file to the local

/**
* @param path 下载后的文件路径和名称
* @param netAddress 文件所在网络地址
* @功能描述 网络文件下载到服务器本地
*/
@RequestMapping("/netDownloadLocal")
public void downloadNet(String netAddress, String path) throws IOException {
    
    
URL url = new URL(netAddress);
URLConnection conn = url.openConnection();
InputStream inputStream = conn.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream(path);
 
int bytesum = 0;
int byteread;
byte[] buffer = new byte[1024];
while ((byteread = inputStream.read(buffer)) != -1) {
    
    
bytesum += byteread;
System.out.println(bytesum);
fileOutputStream.write(buffer, 0, byteread);
}
fileOutputStream.close();
} 

4. After the network file is obtained from the server, it responds to the front end after being processed by the server

/**
* @param netAddress
* @param filename
* @param isOnLine
* @param response
* @功能描述 网络文件获取到服务器后，经服务器处理后响应给前端
*/
@RequestMapping("/netDownLoadNet")
public void netDownLoadNet(String netAddress, String filename, boolean isOnLine, HttpServletResponse response) throws Exception {
    
    
 
URL url = new URL(netAddress);
URLConnection conn = url.openConnection();
InputStream inputStream = conn.getInputStream();
 
response.reset();
response.setContentType(conn.getContentType());
if (isOnLine) {
    
    
// 在线打开方式 文件名应该编码成UTF-8
response.setHeader("Content-Disposition", "inline; filename=" + URLEncoder.encode(filename, "UTF-8"));
} else {
    
    
//纯下载方式 文件名应该编码成UTF-8
response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(filename, "UTF-8"));
}
 
byte[] buffer = new byte[1024];
int len;
OutputStream outputStream = response.getOutputStream();
while ((len = inputStream.read(buffer)) > 0) {
    
    
outputStream.write(buffer, 0, len);
}
inputStream.close();
}