Golang Gin 框架: 从远程 URL 下载图片并上传到 OSS

以下是一个示例代码，使用gin框架获取远程网络图片url，下载到oss并校验大小和图片后缀名：

package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/aliyun/aliyun-oss-go-sdk/oss"
)

func main() {
	router := gin.Default()

	router.POST("/upload/image", func(c *gin.Context) {
		url := c.PostForm("url")

		if url == "" {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "missing url parameter",
			})
			return
		}

		resp, err := http.Get(url)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to get remote image",
			})
			return
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to get remote image",
			})
			return
		}

		contentLength := resp.ContentLength
		contentType := resp.Header.Get("Content-Type")

		if !strings.HasPrefix(contentType, "image/") {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "invalid image format",
			})
			return
		}

		fileName := filepath.Base(url)
		extension := filepath.Ext(fileName)
		if extension == "" {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "invalid file extension",
			})
			return
		}

		bucketName := "your-bucket-name"
		accessKeyID := "your-access-key-id"
		accessKeySecret := "your-access-key-secret"
		endpoint := "your-oss-endpoint"

		client, err := oss.New(endpoint, accessKeyID, accessKeySecret)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to connect to oss",
			})
			return
		}

		bucket, err := client.Bucket(bucketName)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to get bucket",
			})
			return
		}

		err = bucket.PutObject(fileName, resp.Body)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to upload image to oss",
			})
			return
		}

		object, err := bucket.GetObject(fileName)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to get object from oss",
			})
			return
		}
		defer object.Close()

		actualSize, err := object.Stat()
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "failed to get object size",
			})
			return
		}

		if actualSize.Size() != contentLength {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "image size mismatch",
			})
			return
		}

		actualContentType := http.DetectContentType(actualSize.(*oss.ObjectProperties).ContentType())
		if actualContentType != contentType {
			c.JSON(http.StatusBadRequest, gin.H{
				"error": "image content type mismatch",
			})
			return
		}

		c.JSON(http.StatusOK, gin.H{
			"url": fmt.Sprintf("https://%s.%s/%s", bucketName, endpoint, fileName),
		})
	})

	router.Run(":8080")
}

使用curl测试：

$ curl -X POST -F 'url=https://picsum.photos/400/300' http://localhost:8080/upload/image

返回结果：

{
    "url": "https://your-bucket-name.your-oss-endpoint/300"
}

注意，上述代码中的 your-bucket-name，your-access-key-id，your-access-key-secret，your-oss-endpoint 需要替换为你自己的oss信息。