golang 上传文件(包括 gin 实现)

gin

gin是一个用 golang 实现的优秀 web 服务框架

上传文件

标准包实现

package main

import (

	"io"

	"log"

	"net/http"

	"os"

)

var (

  // 文件 key

	uploadFileKey = "upload-key"

)

func main() {

	http.HandleFunc("/upload", uploadHandler)

	if err := http.ListenAndServe(":8080", nil); err != nil {

		log.Fatalf("error to start http server:%s", err.Error())

	}

}

func uploadHandler(w http.ResponseWriter, r *http.Request) {

	// 接受文件

	file, header, err := r.FormFile(uploadFileKey)

	if err != nil {

		// ignore the error handler

	}

	log.Printf("selected file name is %s", header.Filename)

	// 将文件拷贝到指定路径下，或者其他文件操作

	dst, err := os.Create(header.Filename)

	if err != nil {

		// ignore

	}

	_, err = io.Copy(dst, file)

	if err != nil {

		// ignore

	}

}

Gin 实现

package main

import (

	"github.com/gin-gonic/gin"

)

var (

	uploadFileKey = "upload-key"

)

func main() {

	r := gin.Default()

	r.POST("/upload", uploadHandler)

	r.Run()

}

func uploadHandler(c *gin.Context) {

	header, err := c.FormFile(uploadFileKey)

	if err != nil {

		//ignore

	}

	dst := header.Filename

  // gin 简单做了封装,拷贝了文件流

	if err := c.SaveUploadedFile(header, dst); err != nil {

		// ignore

	}

}

SaveUploadedFile 实现如下:

// SaveUploadedFile uploads the form file to specific dst.

func (c *Context) SaveUploadedFile(file *multipart.FileHeader, dst string) error {

	src, err := file.Open()

	if err != nil {

		return err

	}

	defer src.Close()

	//创建 dst 文件

	out, err := os.Create(dst)

	if err != nil {

		return err

	}

	defer out.Close()

// 拷贝文件

	_, err = io.Copy(out, src)

	return err

}

上传文件和参数

有时候除了选中文件外,我们还需要向服务端传递一些参数。在 http multipart 请求格式中。值是以键值对的形式传递的。

标准包实现

Request

文件参数

files :=r.MultipartForm.File

map[string][]*FileHeader

值参数

values := r.MultipartForm.Value

map[string][]string

Gin 实现

ginContext*http.Requestgin

type newForm struct {

	UploadKey *multipart.FileHeader `form:"upload-key"`

	Name      string                `form:"name"`

	Age       int                   `form:"age"`

}

ginShouldBind

	var form newForm

	if err := c.ShouldBind(&form); err != nil{

		//ignore

	}

newFormbinding

Multipart client实现

multipart form 的 client 写法示例

package main

import (

	"bytes"

	"fmt"

	"io"

	"log"

	"mime/multipart"

	"net/http"

	"os"

	"path/filepath"

)

var (

	uploadFileKey = "upload-key"

)

func main() {

	url := "http://127.0.0.1:8080/upload"

	path := "/tmp/test.txt"

	params := map[string]string{

		"key1": "val1",

	}

	req, err := NewFileUploadRequest(url, path, params)

	if err != nil {

		fmt.Printf("error to new upload file request:%s\n", err.Error())

		return

	}

	client := &http.Client{}

	resp, err := client.Do(req)

	if err != nil {

		fmt.Printf("error to request to the server:%s\n", err.Error())

		return

	}

	body := &bytes.Buffer{}

	_, err = body.ReadFrom(resp.Body)

	if err != nil {

		log.Fatal(err)

	}

	defer resp.Body.Close()

	fmt.Println(body)

}

// NewFileUploadRequest ...

func NewFileUploadRequest(url, path string, params map[string]string) (*http.Request, error) {

	file, err := os.Open(path)

	if err != nil {

		return nil, err

	}

	defer file.Close()

	body := &bytes.Buffer{}

	// 文件写入 body

	writer := multipart.NewWriter(body)

	part, err := writer.CreateFormFile(uploadFileKey, filepath.Base(path))

	if err != nil {

		return nil, err

	}

	_, err = io.Copy(part, file)

	// 其他参数列表写入 body

	for k, v := range params {

		if err := writer.WriteField(k, v); err != nil {

			return nil, err

		}

	}

	if err := writer.Close(); err != nil {

		return nil, err

	}

	req, err := http.NewRequest(http.MethodPost, url, body)

	if err != nil {

		return nil, err

	}

	req.Header.Add("Content-Type", writer.FormDataContentType())

	return req, err

}

总结

Gin 的实现方式更加简单高效,框架为我们封装了很多细节。使用起来更加方便。标准库实现相对而言也算简单。但是需要我们自己组织和校验请求参数。

参考