Java实现文件图片的预览和下载功能

    @ApiOperation("访问文件")
    @GetMapping("/download/{name}")
    public void getImage(HttpServletResponse response, @PathVariable("name") String name) throws IOException {
        //动态获取图片存放位置
        //        String path = getUploadPath();//获取当前系统路径
        String path = upload;
        String imagePath = path + File.separator + name;
        if (!new File(imagePath).exists()) {
            return;
        }
        if (name.endsWith("jpg") || name.endsWith("png") || name.endsWith("gif") || name.endsWith("jpeg")) {
            //预览时不需设置Content-Disposition
            response.setContentType("image/jpeg;charset=utf-8");//图片
        }else {
            //下载
        response.setContentType("application/octet-stream");//文件
        response.setHeader("Content-Disposition", "inline; filename=" + URLEncoder.encode(name, "UTF-8"));
        }
        ServletOutputStream outputStream = response.getOutputStream();
        outputStream.write(Files.readAllBytes(Paths.get(path).resolve(name)));
        outputStream.flush();
        outputStream.close();
    }

package com.example.controller;

import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;
import java.nio.file.Files;

@RestController
@RequestMapping("/api/files")
public class FileDownloadController {

    @GetMapping("/download")
    public ResponseEntity<Resource> downloadFile() {
        String fileName = "example.txt"; // 要下载的文件名
        
        try {
            // 从 resources 目录加载文件
            ClassPathResource resource = new ClassPathResource(fileName);
            
            if (!resource.exists()) {
                return ResponseEntity.notFound().build();
            }

            // 设置响应头
            HttpHeaders headers = new HttpHeaders();
            headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + resource.getFilename());

            // 返回文件作为响应
            return ResponseEntity.ok()
                    .headers(headers)
                    .contentType(org.springframework.http.MediaType.APPLICATION_OCTET_STREAM)
                    .body(resource);
        } catch (IOException e) {
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
        }
    }
}

package com.example.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.OutputStream;

/**
 * @author long
 * @version 1.0.0
 * @ClassName FileController
 * @Description TODO
 * @createTime 2022.03.18 18:47
 */
@RestController
@RequestMapping("/demo")
public class FileController {


    @GetMapping("/file")
    public void filePreviewOrDownload(HttpServletRequest request, HttpServletResponse response) throws Exception {
        String fileName = request.getParameter("fileName");
        //type. p预览，d下载
        String type = request.getParameter("type");
        response.reset();
        response.setCharacterEncoding("UTF-8");

        File file = new File("C:\\Users\\long\\Desktop\\" + fileName);
        FileInputStream fis = new FileInputStream(file);

        if ("d".equalsIgnoreCase(type)) {
            //下载
            response.setContentType("application/octet-stream");
            response.setHeader("Content-Disposition", "attachment;filename*=utf-8''" + System.currentTimeMillis() + fileName.substring(fileName.lastIndexOf(".")));

        } else {
            //预览时不需设置Content-Disposition
//            response.setContentType("application/octet-stream");
//            response.setContentType("text/html;charset=UTF-8");
//            response.setHeader("Content-Disposition","inline;filename=" + System.currentTimeMillis() + fileName.substring(fileName.lastIndexOf(".")));
        }
        OutputStream os = response.getOutputStream();
        byte[] bytes = new byte[1024];
        int length = 0;
        while ((length = fis.read(bytes)) != -1) {
            os.write(bytes, 0, length);
        }
        os.close();
        fis.close();
    }


}

@GetMapping("/downFile")
    public void downFile(HttpServletResponse response, HttpServletRequest request) {
        try {
//            File file = new File("C:\\Users\\hnsh\\Pictures\\铁山靠.png");
            File file = new File("F:\\BaiduNetdiskDownload\\activiti教程 (1).pdf");
            String filename = file.getName();
            String fileType = filename.substring(filename.indexOf(".") + 1);

            // 以流的形式下载文件。
            FileInputStream fileInputStream = new FileInputStream(file);
            InputStream fis = new BufferedInputStream(fileInputStream);
            byte[] buffer = new byte[1024];
            int len = 0;
            // 清空response
            response.reset();
            // 设置response的Header
            // 解决跨域
            response.addHeader("Access-Control-Allow-Origin", "*");
            boolean b = "jpg".equalsIgnoreCase(fileType) || "png".equalsIgnoreCase(fileType) || "gif".equalsIgnoreCase(fileType);
            // 图片预览
            if (b) {
                response.setContentType("image/" + fileType);
            } else if ("pdf".equalsIgnoreCase(fileType)) {
                // pdf 预览
                response.setContentType("application/pdf");
            } else {
                // 直接下载
                response.setContentType("application/text;chartset=utf-8");
                response.addHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));
                response.addHeader("Content-Length", "" + file.length());
            }
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            int a = 0;
            while ((len = fis.read(buffer)) != -1) {
                a = len + a;
                toClient.write(buffer, 0, len);
            }
            toClient.flush();
            toClient.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }