yvjia/src/main/java/com/backendsys/modules/download/controller/DownloadLocalController.java

package com.backendsys.modules.download.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.InputStreamResource;
import org.springframework.core.io.Resource;
import org.springframework.http.*;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;

/**
 * 下载本地文件
 */
@RestController
public class DownloadLocalController {

    @Value("${file.upload.directory}") // 配置保存文件的目录
    private String uploadDirectory;

    // 判断文件是否为图片文件
    private boolean isImageFile(File file) {
        String extension = getExtension(file.getName());
        return Arrays.asList("jpg", "jpeg", "png", "gif").contains(extension.toLowerCase());
    }

    // 获取图片文件对应的MediaType
    private MediaType getImageMediaType(File file) {
        String extension = getExtension(file.getName());
        switch (extension.toLowerCase()) {
            case "jpg":
            case "jpeg": return MediaType.IMAGE_JPEG;
            case "png": return MediaType.IMAGE_PNG;
            case "gif": return MediaType.IMAGE_GIF;
            default: return MediaType.APPLICATION_OCTET_STREAM;
        }
    }

    public static String getExtension(String filename) {
        if (filename == null) { return ""; }
        int dotIndex = filename.lastIndexOf(".");
        if (dotIndex > 0 && dotIndex < filename.length() - 1) {
            return filename.substring(dotIndex + 1);
        }
        return "";
    }

    @GetMapping("/uploads/{folder}/{filename:.+}")
    public ResponseEntity<Resource> serveFile(@PathVariable String folder, @PathVariable String filename) throws IOException {

        File file = new File(uploadDirectory + folder + "/" + filename);
        // 如果是图片，则直接显示；如果是文件，则是下载
        HttpHeaders headers = new HttpHeaders();
        if (isImageFile(file)) {
            // 如果是图片文件，设置Content-Type为对应的图片MIME类型
            headers.setContentType(getImageMediaType(file));
        } else {
            // 如果不是图片文件，设置Content-Disposition以附件形式下载
            headers.setContentDisposition(ContentDisposition.attachment().filename(file.getName()).build());
            headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        }
        if (!file.exists()) {
            String message = "图片不存在";
            InputStream inputStream = new ByteArrayInputStream(message.getBytes(StandardCharsets.UTF_8));
            InputStreamResource resource = new InputStreamResource(inputStream);
            return ResponseEntity.status(HttpStatus.NOT_FOUND)
                    .contentType(MediaType.valueOf("text/plain; charset=UTF-8"))
                    .body(resource);
        }
        InputStreamResource resource = new InputStreamResource(new FileInputStream(file));
        return ResponseEntity.ok()
                .headers(headers)
                .contentLength(file.length())
                //.header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + file.getName() + "\"")
                //.contentType(MediaType.APPLICATION_OCTET_STREAM)
                .body(resource);
    }

}