java文件下载前后端代码实现
程序员文章站
2022-03-15 10:16:51
...
后端
@WebServlet("/downloadServlet")
public class DownloadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取请求参数，文件名称
String filename = request.getParameter("filename");
//2.使用字节输入流加载文件进内存
//2.1找到文件服务器路径
ServletContext servletContext = this.getServletContext();
String realPath = servletContext.getRealPath("/img/" + filename);
//2.2用字节流关联
FileInputStream fis = new FileInputStream(realPath);
//3.设置response的响应头
//3.1设置响应头类型：content-type
String mimeType = servletContext.getMimeType(filename);//获取文件的mime类型
response.setHeader("content-type",mimeType);
//3.2设置响应头打开方式:content-disposition
//解决中文文件名问题
//1.获取user-agent请求头、
String agent = request.getHeader("user-agent");
//2.使用工具类方法编码文件名即可
filename = DownLoadUtils.getFileName(agent, filename);
response.setHeader("content-disposition","attachment;filename="+filename);
//4.将输入流的数据写出到输出流中
ServletOutputStream sos = response.getOutputStream();
byte[] buff = new byte[1024 * 8];
int len = 0;
while((len = fis.read(buff)) != -1){
sos.write(buff,0,len);
}
fis.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
前端页面
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a href="/downloadServlet?filename=xx.jpg">图片1</a>
</body>
</html>
工具类
public class DownLoadUtils {
public static String getFileName(String agent, String filename) throws UnsupportedEncodingException {
if (agent.contains("MSIE")) {
// IE浏览器
filename = URLEncoder.encode(filename, "utf-8");
filename = filename.replace("+", " ");
} else if (agent.contains("Firefox")) {
// 火狐浏览器
BASE64Encoder base64Encoder = new BASE64Encoder();
filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
} else {
// 其它浏览器
filename = URLEncoder.encode(filename, "utf-8");
}
return filename;
}
}