Springboot中如何将本地文件以流的形式返回给前端下载

  ***Springboot中如何将本地文件以流的形式返回给前端下载***

代码展示：

package gaea.ImportService.utils;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLDecoder;
import java.net.URLEncoder;
public class OutPutStreams {
private static final Logger logger = LoggerFactory.getLogger(OutPutStreams.class);

/**
 * 响应体加入文件流
 * @param response
 * @param filePath	文件从盘符开始的完整路径
 */
public static void buildExcelDocument(HttpServletResponse response, String filePath){
    logger.debug("responseFileStream imgPath:"+filePath);
    if(filePath.contains("%")){
        try {
            filePath = URLDecoder.decode(filePath,"UTF-8");
        } catch (UnsupportedEncodingException e) {
            logger.debug("responseFileStream decode error:"+e.toString());
        }
    }
    if(filePath.contains("%")){
        try {
            filePath = URLDecoder.decode(filePath,"UTF-8");
        } catch (UnsupportedEncodingException e) {
            logger.debug("responseFileStream decode error:"+e.toString());
        }
    }

    ServletOutputStream out = null;
    FileInputStream in = null;
    try {
        in = new FileInputStream(new File(filePath));
        String[] dir = filePath.split("/");
        String fileName = dir[dir.length-1];
        String[] array = fileName.split("[.]");
        String fileType = array[array.length-1].toLowerCase();
        //设置文件ContentType类型
        if("jpg,jepg,gif,png".contains(fileType)){//图片类型
            response.setContentType("image/"+fileType);
        }else if("pdf".contains(fileType)){//pdf类型
            response.setContentType("application/pdf");
        }else{//自动判断下载文件类型
            response.setContentType("multipart/form-data");
        }
        //设置文件头：最后一个参数是设置下载文件名
        //response.setHeader("Content-Disposition", "attachment;fileName="+fileName);
        out = response.getOutputStream();
        // 读取文件流
        int len = 0;
        byte[] buffer = new byte[1024 * 10];
        while ((len = in.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
        out.flush();
    } catch (FileNotFoundException e) {
        logger.error("responseFileStream error:FileNotFoundException" + e.toString());
    } catch (Exception e) {
        logger.error("responseFileStream error:" + e.toString());
    } finally {
        try {
            out.close();
            in.close();
        } catch (NullPointerException e) {
            logger.error("responseFileStream stream close() error:NullPointerException" + e.toString());
        } catch (Exception e) {
            logger.error("responseFileStream stream close() error:" + e.toString());
        }
    }
}

}