【Java】下载文件的工具类

jdk1.8

package com.yitong.sny.common.utils;

import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;

import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;
import java.nio.file.Files;
import java.nio.file.Path;

/**
 * 未完成，待补充，需要继续参考：
 * https://www.jb51.net/article/241277.htm
 * @date 2023-02-20
 */
public class DownloadUtil {

    /**
     * 设置下载
     *
     * @param response    此次响应的对象
     * @param contentType 内容类型
     * @param filename    文件名
     * @throws UnsupportedEncodingException 转换文件名编码时出现错误
     */
    public static void setDownloadInfo(HttpServletResponse response, String contentType, String filename) throws UnsupportedEncodingException {
        response.setContentType(contentType);
        response.setCharacterEncoding("UTF-8");
        response.setHeader("Content-Disposition", "attachment;filename=" + java.net.URLEncoder.encode(filename, "UTF-8"));
    }

    /**
     * 输出流
     *
     * @param response    响应
     * @param contentType 资源类型
     * @param filepath    文件路径
     * @return 返回是否输出成功
     * @throws UnsupportedEncodingException 不支持的编码异常
     */
    public boolean output(HttpServletResponse response, String contentType, String filepath) throws UnsupportedEncodingException {
        File file = new File(filepath);//创建下载的目标文件，参数为文件的真实路径
        if (file.exists()) { //判断文件是否存在
            setDownloadInfo(response, contentType, file.getName());
            byte[] buffer = new byte[1024];
            try (
                    FileInputStream fis = new FileInputStream(file);
                    BufferedInputStream bis = new BufferedInputStream(fis);
                    OutputStream os = response.getOutputStream()    // 输出流
            ) {
                int i = bis.read(buffer);
                while (i != -1) {
                    os.write(buffer);
                    i = bis.read(buffer);
                }
                return true;
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return false;
    }

    /**
     * 响应 resource 目录下的文件资源
     *
     * @param filepath resource 下的文件资源路径（相对路径，比如传入参数值：<code>"static/image/pic.png"</code>）
     */
    public static ResponseEntity<Resource> getResponseResourceByClassPath(String filepath) throws IOException {
        ClassPathResource resource = new ClassPathResource(filepath);
        String returnName = new File(filepath).getName();
        return getResponseResource(resource, returnName, MediaType.APPLICATION_OCTET_STREAM);
    }

    /**
     * 响应到前端页面
     *
     * @return 返回响应的资源
     */
    public static ResponseEntity<Resource> getResponseResource(String filepath) throws IOException {
        Path path = new File(filepath).toPath();
        MediaType mediaType;
        if (new File(filepath).exists()) {
            try {
                String contentType = Files.probeContentType(path);
                mediaType = MediaType.parseMediaType(contentType);
            } catch (Exception e) {
                mediaType = MediaType.APPLICATION_OCTET_STREAM;
            }
        } else {
            mediaType = MediaType.APPLICATION_OCTET_STREAM;
        }
        return getResponseResource(filepath, mediaType);
    }

    public static ResponseEntity<Resource> getResponseResource(String filepath, MediaType mediaType) throws IOException {
        Path path = new File(filepath).toPath();
        Path fileName = path.getFileName();
        return getResponseResource(filepath, fileName.toString(), mediaType);
    }

    public static ResponseEntity<Resource> getResponseResource(String filepath, String returnName, MediaType mediaType) throws IOException {
        Path path = new File(filepath).toPath();
        FileSystemResource resource = new FileSystemResource(path);
        return getResponseResource(resource, returnName, mediaType);
    }

    public static ResponseEntity<Resource> getResponseResource(Resource resource, String returnName, MediaType mediaType) throws IOException {
        returnName = URLEncoder.encode(returnName, "utf-8");
        return ResponseEntity.ok()
                .contentType(mediaType)
                .header("Content-disposition", "attachment; filename=" + returnName)
                .body(resource);
    }

}