下載文件時，響應Response設置，瀏覽器彈出下載框

在你瀟灑的寫下InputStream轉到response的時候，需要先設置下Response，否則瀏覽器並不會彈出下載框

預處理

"Content-Type", "application/octet-stream"是內容類型，告訴瀏覽器這個是什麼，可以參照對照表
https://www.runoob.com/http/http-content-type.html

public static void preInitResponseForFileStream(HttpServletResponse response, String name) {
        response.reset();
        //避免中文亂碼
        response.setHeader("Content-Disposition", "attachment;filename=" + new String(name.getBytes(), StandardCharsets.ISO_8859_1));
        response.setHeader("Connection", "close");
        //設置傳輸的類型
        response.setHeader("Content-Type", "application/octet-stream");
        response.setHeader("Content-Transfer-Encoding", "chunked");
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setContentType("application/OCTET-STREAM");
    }

下載

這裏也順便把下載貼上來吧，也可以使用其他流的處理方式，比如java7的Files工具類等，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();
        }
    }