Java上传文件、下载文件、预览文件

一、上传文件

@PostMapping("/upload")
    public String uploadSystem(MultipartFile file){
        String url = "";
        try{
            String name = file.getOriginalFilename().substring(0,file.getOriginalFilename().indexOf(".")+ ".".length()-1);
            String imgName =name+"_"+ DateUtils.dateTimeNow();

            if (file == null) {
                log.error("==>  没有上传文件。");
                return ("没有上传文件。");
            }
            log.info("==>文件名: " + file.getOriginalFilename());
            url = fileService.handlerMultipartFile(file,imgName);

            log.info("==>文件路径: " + url);
        }
        catch (Exception e){

        }

        return url;
    }

二、下载文件

/**
     * 下载通用配置指导书
     * @param
     * @param response
     * @param filePath  文件路径
     */

    public void downloadInstruction(HttpServletResponse response, String filePath) {
//        File file = new File(filePath);
        File file = new File(filePath);
        String fileName = file.getName();
        InputStream fis = null;
        try {
            fis = new FileInputStream(file);
            response.reset();
            response.setCharacterEncoding("UTF-8");
            response.setContentType("application/PDF;charset=utf-8");
            response.setHeader("content-disposition", "attachement;fileName=" + new String(fileName.getBytes("utf-8"), "ISO-8859-1"));
            byte[] bytes = new byte[1024];
            int len;
            while ((len = fis.read(bytes)) != -1) {
                response.getOutputStream().write(bytes, 0, len);
            }
            response.flushBuffer();
            fis.close();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
//        return "下载成功";
    }

三、预览文件

public void preview( HttpServletResponse response,String filePath) throws
            IOException {
        FileInputStream is = new FileInputStream(new File(filePath));
        // 清空response
        response.reset();
        //2、设置文件下载方式
        response.setCharacterEncoding("utf-8");
        response.setContentType("application/pdf");
        OutputStream outputStream = response.getOutputStream();
        int count = 0;
        byte[] buffer = new byte[1024 * 1024];
        while ((count = is.read(buffer)) != -1) {
            outputStream.write(buffer, 0, count);
        }
        outputStream.flush();

    }

FileService

package com.ruoyi.zw.controller;

/**
 * @author: cyf
 * @Date: 2023/3/27 19:08
 */

import com.ruoyi.common.config.RuoYiConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;

@Service
public class FileService {
    protected static final Logger logger= LoggerFactory.getLogger(FileService.class);

    private String directoryPath = RuoYiConfig.getFile();

    public FileService() {
        File directory = new File(directoryPath);
        if (!directory.exists()) {
            directory.mkdirs();
        }
    }

    public String handlerMultipartFile(MultipartFile multipartFile ,String unid) {
        String fileOldName = multipartFile.getOriginalFilename();
        int beginIndex = fileOldName.lastIndexOf(".");
        String suffix = fileOldName.substring(beginIndex);
        String newFileName =  unid+ suffix;
        File upFile = new File(directoryPath + "/" + newFileName);
        OutputStream outputStream = null;
        try {
            byte[] fileByte = multipartFile.getBytes();
            outputStream = new FileOutputStream(upFile);
            outputStream.write(fileByte);
            logger.info("<==  文件写出完成: " + newFileName);
            return  newFileName;
        } catch (Exception e) {
            logger.error("", e);
        } finally {
            try {
                if (outputStream != null) {
                    outputStream.flush();
                    outputStream.close();
                }
            } catch (Exception e) {
                logger.error("", e);
            }
        }
        return  newFileName;
    }

}