下载文件时，响应Response设置，浏览器弹出下载框

在你潇洒的写下InputStream转到response的时候，需要先设置下Response，否则浏览器并不会弹出下载框

预处理

"Content-Type", "application/octet-stream"是内容类型，告诉浏览器这个是什么，可以参照对照表
https://www.runoob.com/http/http-content-type.html

public static void preInitResponseForFileStream(HttpServletResponse response, String name) {
        response.reset();
        //避免中文乱码
        response.setHeader("Content-Disposition", "attachment;filename=" + new String(name.getBytes(), StandardCharsets.ISO_8859_1));
        response.setHeader("Connection", "close");
        //设置传输的类型
        response.setHeader("Content-Type", "application/octet-stream");
        response.setHeader("Content-Transfer-Encoding", "chunked");
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setContentType("application/OCTET-STREAM");
    }

下载

这里也顺便把下载贴上来吧，也可以使用其他流的处理方式，比如java7的Files工具类等，或者apache的IOUtils

public static void download(String fileUrl, HttpServletResponse response) {
        try (BufferedInputStream in = new BufferedInputStream(new URL(fileUrl).openStream());
             BufferedOutputStream out = new BufferedOutputStream(response.getOutputStream())) {
            byte dataBuffer[] = new byte[1024];
            int bytesRead;
            while ((bytesRead = in.read(dataBuffer, 0, 1024)) != -1) {
                out.write(dataBuffer, 0, bytesRead);
            }
            out.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }