当SpringBoot遇上腾讯云COS，你的文件有个“云上别墅”

<dependency>
       <groupId>com.qcloud</groupId>
       <artifactId>cos_api</artifactId>
       <version>5.6.227</version> <!-- 可使用当前最新稳定版 -->
   </dependency>

package com.yourproject.config;
   import com.qcloud.cos.COSClient;
   import com.qcloud.cos.ClientConfig;
   import com.qcloud.cos.auth.BasicCOSCredentials;
   import com.qcloud.cos.auth.COSCredentials;
   import com.qcloud.cos.region.Region;
   import lombok.Data;
   import org.springframework.boot.context.properties.ConfigurationProperties;
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   
   @Configuration
   @ConfigurationProperties(prefix = "cos.client") // 从配置文件读取cos.client下的属性
   @Data // Lombok注解，自动生成getter/setter
   public class CosClientConfig {
       // 对应配置文件里的 cos.client.host
       private String host; 
       private String secretId;
       private String secretKey;
       private String region;
       private String bucketName;
   
       @Bean
       public COSClient cosClient() {
           // 1. 初始化身份信息（门卡和密码）
           COSCredentials cred = new BasicCOSCredentials(secretId, secretKey);
           // 2. 设置存储桶的地域
           ClientConfig clientConfig = new ClientConfig(new Region(region));
           // 3. 生成COS客户端
           return new COSClient(cred, clientConfig);
       }
   }

# 腾讯云COS配置
   cos:
     client:
       host: https://your-bucket-name.cos.ap-guangzhou.myqcloud.com # 你的存储桶访问域名（非必须，可用于拼接URL）
       secret-id: your-secret-id-here # 替换为你的SecretId
       secret-key: your-secret-key-here # 替换为你的SecretKey
       region: ap-guangzhou # 替换为你的存储桶地域，如ap-beijing
       bucket-name: myblog-1250000000 # 替换为你的存储桶名称

package com.yourproject.manager;
import com.qcloud.cos.COSClient;
import com.qcloud.cos.model.*;
import com.yourproject.config.CosClientConfig;
import org.springframework.stereotype.Component;
import javax.annotation.Resource;
import java.io.File;

@Component
public class CosManager {
    @Resource
    private CosClientConfig cosClientConfig;
    @Resource
    private COSClient cosClient;

    /**
     * 上传文件到COS（简单上传，适用于小文件）
     * @param key 对象键，即文件在COS中的完整路径，如 "images/avatar.jpg"
     * @param file 本地文件
     * @return 上传结果
     */
    public PutObjectResult uploadFile(String key, File file) {
        // 创建上传请求，参数：桶名，对象键，本地文件
        PutObjectRequest putObjectRequest = new PutObjectRequest(cosClientConfig.getBucketName(), key, file);
        // 执行上传
        return cosClient.putObject(putObjectRequest);
    }

    /**
     * 下载文件
     * @param key 对象键
     * @return COS对象，包含文件的输入流等信息
     */
    public COSObject downloadFile(String key) {
        GetObjectRequest getObjectRequest = new GetObjectRequest(cosClientConfig.getBucketName(), key);
        return cosClient.getObject(getObjectRequest);
    }

    /**
     * 删除文件
     * @param key 对象键
     */
    public void deleteFile(String key) {
        cosClient.deleteObject(cosClientConfig.getBucketName(), key);
    }
}

package com.yourproject.controller;
import com.yourproject.manager.CosManager;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.io.IOUtils;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import javax.annotation.Resource;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.UUID;

@RestController
@RequestMapping("/cos")
@Slf4j
public class CosController {
    @Resource
    private CosManager cosManager;

    @PostMapping("/upload")
    public String upload(@RequestPart("file") MultipartFile multipartFile) {
        // 生成唯一文件名，防止覆盖
        String originalFilename = multipartFile.getOriginalFilename();
        String fileExtension = originalFilename.substring(originalFilename.lastIndexOf("."));
        String key = "upload/" + UUID.randomUUID() + fileExtension; // 存储在upload目录下
        
        File tempFile = null;
        try {
            // 创建临时文件
            tempFile = File.createTempFile("cos-upload-", null);
            multipartFile.transferTo(tempFile);
            // 调用Manager上传
            cosManager.uploadFile(key, tempFile);
            // 返回文件的访问路径（如果是私有读，此处应返回一个预签名URL）
            return String.format("文件上传成功！Key: %s", key);
        } catch (IOException e) {
            log.error("文件上传失败", e);
            return "上传失败";
        } finally {
            // 清理临时文件
            if (tempFile != null && tempFile.exists()) {
                boolean deleted = tempFile.delete();
                if (!deleted) {
                    log.warn("临时文件删除失败: {}", tempFile.getAbsolutePath());
                }
            }
        }
    }

    @GetMapping("/download")
    public void download(@RequestParam String key, HttpServletResponse response) throws IOException {
        // 通过key获取COS中的文件对象
        try (COSObject cosObject = cosManager.downloadFile(key)) {
            if (cosObject == null) {
                response.sendError(404, "文件不存在");
                return;
            }
            // 设置响应头，告诉浏览器这是附件下载
            response.setContentType("application/octet-stream");
            response.setHeader("Content-Disposition", "attachment; filename=\"" + key.substring(key.lastIndexOf("/") + 1) + "\"");
            
            // 将COS文件流写入HTTP响应流
            try (InputStream cosInput = cosObject.getObjectContent()) {
                IOUtils.copy(cosInput, response.getOutputStream());
                response.flushBuffer();
            }
        } catch (Exception e) {
            log.error("文件下载失败， key: {}", key, e);
            response.sendError(500, "下载失败");
        }
    }
}

// 在CosManager中增加生成预签名URL的方法
   public String generatePresignedUrl(String key, Date expirationTime) {
       GeneratePresignedUrlRequest req = new GeneratePresignedUrlRequest(cosClientConfig.getBucketName(), key, HttpMethodName.GET);
       req.setExpiration(expirationTime);
       return cosClient.generatePresignedUrl(req).toString();
   }