Springboot如何通过流返回文件

    @GetMapping(value = "/downfile")
    public void download(HttpServletResponse response) throws IOException {
        String fileName = "template.xlsx";
        // 设置信息给客户端不解析
        String type = new MimetypesFileTypeMap().getContentType(fileName);
        // 设置contenttype，即告诉客户端所发送的数据属于什么类型
        response.setHeader("Content-type",type);
        // 设置编码
        String code = new String(fileName.getBytes("utf-8"), "iso-8859-1");
        // 设置扩展头，当Content-Type 的类型为要下载的类型时 , 这个信息头会告诉浏览器这个文件的名字和类型。
        response.setHeader("Content-Disposition", "attachment;filename=" + code);
        response.setContentType("application/octet-stream;charset=ISO8859-1");
        response.addHeader("Pargam", "no-cache");
        response.addHeader("Cache-Control", "no-cache");
        DownLoadUtils.download(fileName, response);
    }

public class DownLoadUtils { 
    public static void download(String filename, HttpServletResponse res) throws IOException {
        // 发送给客户端的数据
        // 读取filename
        ClassPathResource classPathResource = new ClassPathResource("templates/"+filename);
        long length = classPathResource.getFile().length();
        res.addHeader("Content-Length",String.valueOf(length));
        OutputStream outputStream = res.getOutputStream();
        byte[] buff = new byte[1024];
        BufferedInputStream bis = null;
        InputStream inputStream =classPathResource.getInputStream();
        bis = new BufferedInputStream(inputStream);
        int i = bis.read(buff);
        while (i != -1) {
            outputStream.write(buff, 0, buff.length);
            outputStream.flush();
            i = bis.read(buff);
        }
        bis.close();
        outputStream.close();
    }
}

response.addHeader("Content-Length",String.valueOf(file.length()));

import java.io.FileReader;
import java.io.InputStream;
import java.util.Properties;
/*
 */
public class Reflect {
    public static void main(String[] args) throws Exception{
       //获取一个文件的绝对路径！！！
        // 这种是先获得绝对路径然后在转换成流。
//        String path = Thread.currentThread().getContextClassLoader()
//                .getResource("classinfo2.properties").getPath();
//        FileReader reader = new FileReader(path);
        //下面这种是直接用流的方式返回。
        InputStream reader = Thread.currentThread().getContextClassLoader()
                .getResourceAsStream("classinfo2.properties");
        Properties pro = new Properties();
        pro.load(reader);
        reader.close();
        //通过key获取value。
        String className = pro.getProperty("className");
        System.out.println(className);
    }
}