Gin 框架中如何实现文件上传和下载?

Gin 框架中的文件上传和下载实现方法如下:

1. 文件上传

1.1 单文件上传

go
func uploadFile(c *gin.Context) {
    file, err := c.FormFile("file")
    if err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
    
    // 保存文件
    dst := "./uploads/" + file.Filename
    if err := c.SaveUploadedFile(file, dst); err != nil {
        c.JSON(500, gin.H{"error": err.Error()})
        return
    }
    
    c.JSON(200, gin.H{
        "message": "File uploaded successfully",
        "filename": file.Filename,
        "size": file.Size,
    })
}

1.2 多文件上传

go
func uploadMultipleFiles(c *gin.Context) {
    form, err := c.MultipartForm()
    if err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
    
    files := form.File["files"]
    var uploadedFiles []string
    
    for _, file := range files {
        dst := "./uploads/" + file.Filename
        if err := c.SaveUploadedFile(file, dst); err != nil {
            c.JSON(500, gin.H{"error": err.Error()})
            return
        }
        uploadedFiles = append(uploadedFiles, file.Filename)
    }
    
    c.JSON(200, gin.H{
        "message": "Files uploaded successfully",
        "files": uploadedFiles,
    })
}

1.3 文件大小限制

go
func uploadFileWithLimit(c *gin.Context) {
    // 限制文件大小为 10MB
    c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 10<<20)
    
    file, err := c.FormFile("file")
    if err != nil {
        c.JSON(400, gin.H{"error": "File too large"})
        return
    }
    
    // 处理文件上传...
}

1.4 文件类型验证

go
func uploadFileWithValidation(c *gin.Context) {
    file, err := c.FormFile("file")
    if err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
    
    // 验证文件类型
    allowedTypes := []string{"image/jpeg", "image/png", "image/gif"}
    fileHeader, err := file.Open()
    if err != nil {
        c.JSON(500, gin.H{"error": err.Error()})
        return
    }
    defer fileHeader.Close()
    
    buffer := make([]byte, 512)
    _, err = fileHeader.Read(buffer)
    if err != nil {
        c.JSON(500, gin.H{"error": err.Error()})
        return
    }
    
    contentType := http.DetectContentType(buffer)
    isAllowed := false
    for _, allowedType := range allowedTypes {
        if contentType == allowedType {
            isAllowed = true
            break
        }
    }
    
    if !isAllowed {
        c.JSON(400, gin.H{"error": "Invalid file type"})
        return
    }
    
    // 处理文件上传...
}

2. 文件下载

2.1 简单文件下载

go
func downloadFile(c *gin.Context) {
    filename := c.Param("filename")
    filepath := "./uploads/" + filename
    
    c.File(filepath)
}

2.2 带自定义文件名的下载

go
func downloadFileWithCustomName(c *gin.Context) {
    filename := c.Param("filename")
    filepath := "./uploads/" + filename
    
    c.FileAttachment(filepath, "custom-name.pdf")
}

2.3 流式下载

go
func downloadFileStream(c *gin.Context) {
    filename := c.Param("filename")
    filepath := "./uploads/" + filename
    
    file, err := os.Open(filepath)
    if err != nil {
        c.JSON(404, gin.H{"error": "File not found"})
        return
    }
    defer file.Close()
    
    fileInfo, _ := file.Stat()
    c.Header("Content-Disposition", "attachment; filename="+filename)
    c.Header("Content-Type", "application/octet-stream")
    c.Header("Content-Length", strconv.FormatInt(fileInfo.Size(), 10))
    
    http.ServeContent(c.Writer, c.Request, filename, fileInfo.ModTime(), file)
}

2.4 断点续传下载

go
func downloadFileWithResume(c *gin.Context) {
    filename := c.Param("filename")
    filepath := "./uploads/" + filename
    
    file, err := os.Open(filepath)
    if err != nil {
        c.JSON(404, gin.H{"error": "File not found"})
        return
    }
    defer file.Close()
    
    fileInfo, _ := file.Stat()
    
    // 处理 Range 请求
    rangeHeader := c.GetHeader("Range")
    if rangeHeader != "" {
        // 解析 Range 头
        ranges := strings.Split(rangeHeader, "=")[1]
        parts := strings.Split(ranges, "-")
        start, _ := strconv.ParseInt(parts[0], 10, 64)
        
        file.Seek(start, 0)
        remaining := fileInfo.Size() - start
        
        c.Header("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, fileInfo.Size()-1, fileInfo.Size()))
        c.Header("Content-Length", strconv.FormatInt(remaining, 10))
        c.Header("Accept-Ranges", "bytes")
        c.Status(206) // Partial Content
        
        io.CopyN(c.Writer, file, remaining)
        return
    }
    
    c.Header("Accept-Ranges", "bytes")
    http.ServeContent(c.Writer, c.Request, filename, fileInfo.ModTime(), file)
}

3. 最佳实践

3.1 文件存储

• 使用专门的存储服务(如 OSS、S3)
• 文件名使用 UUID 或时间戳避免冲突
• 按日期或用户分目录存储

3.2 安全考虑

• 验证文件类型和大小
• 扫描上传的文件(病毒检测)
• 限制上传目录的访问权限
• 对敏感文件进行加密

3.3 性能优化

• 使用流式处理大文件
• 实现断点续传
• 使用 CDN 加速文件下载
• 启用 gzip 压缩

3.4 错误处理

• 提供清晰的错误信息
• 记录上传下载日志
• 实现重试机制

通过以上方法,可以实现安全、高效的文件上传和下载功能。