Golang HTTP文件上传中间件gulter使用指南

gulter是一个轻量级的Golang中间件，用于简化HTTP文件上传处理。下面我将详细介绍如何使用gulter处理文件上传需求。

安装gulter

首先安装gulter包：

go get github.com/thewizardplusplus/go-gulter

基本用法

package main

import (
	"fmt"
	"log"
	"net/http"
	
	"github.com/thewizardplusplus/go-gulter"
)

func main() {
	// 创建gulter中间件实例
	uploadMiddleware := gulter.New(gulter.Config{
		// 上传文件存储目录
		UploadDir: "./uploads",
		// 允许的最大文件大小(字节)
		MaxFileSize: 10 << 20, // 10MB
		// 允许的MIME类型
		AllowedMimeTypes: []string{
			"image/jpeg",
			"image/png",
			"application/pdf",
		},
	})

	// 创建HTTP处理函数
	uploadHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 从上下文中获取上传的文件信息
		files, ok := r.Context().Value(gulter.UploadedFilesContextKey).([]gulter.UploadedFile)
		if !ok {
			http.Error(w, "no files uploaded", http.StatusBadRequest)
			return
		}

		// 处理上传的文件
		for _, file := range files {
			fmt.Fprintf(w, "File uploaded: %s, Size: %d, MIME: %s\n", 
				file.Filename, file.Size, file.MimeType)
		}
	})

	// 应用中间件
	http.Handle("/upload", uploadMiddleware(uploadHandler))

	log.Println("Server started on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

高级配置

gulter提供了多种配置选项：

uploadMiddleware := gulter.New(gulter.Config{
	UploadDir: "./uploads",
	MaxFileSize: 5 << 20, // 5MB
	AllowedMimeTypes: []string{"image/*"}, // 允许所有图片类型
	FieldName: "custom_file_field", // 默认是"file"
	RandomFilename: true, // 生成随机文件名
	Overwrite: false, // 不允许覆盖已有文件
	Multiple: true, // 允许多文件上传
})

文件验证

你可以在处理函数中添加自定义验证：

uploadHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
	files, ok := r.Context().Value(gulter.UploadedFilesContextKey).([]gulter.UploadedFile)
	if !ok {
		http.Error(w, "no files uploaded", http.StatusBadRequest)
		return
	}

	for _, file := range files {
		// 自定义验证逻辑
		if file.Size > 2<<20 { // 2MB
			http.Error(w, fmt.Sprintf("file %s is too large", file.Filename), http.StatusBadRequest)
			return
		}
		
		// 处理文件...
	}
})

错误处理

gulter会返回详细的错误信息：

uploadHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
	if err, ok := r.Context().Value(gulter.UploadErrorContextKey).(error); ok {
		switch err {
		case gulter.ErrNoFileUploaded:
			http.Error(w, "请选择要上传的文件", http.StatusBadRequest)
		case gulter.ErrFileTooLarge:
			http.Error(w, "文件大小超过限制", http.StatusBadRequest)
		case gulter.ErrInvalidFileType:
			http.Error(w, "不支持的文件类型", http.StatusBadRequest)
		default:
			http.Error(w, "上传文件时出错", http.StatusInternalServerError)
		}
		return
	}
	
	// 正常处理...
})

完整示例

下面是一个完整的文件上传服务示例：

package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	
	"github.com/thewizardplusplus/go-gulter"
)

func main() {
	// 确保上传目录存在
	if err := os.MkdirAll("./uploads", 0755); err != nil {
		log.Fatal(err)
	}

	// 配置gulter中间件
	uploadMiddleware := gulter.New(gulter.Config{
		UploadDir:        "./uploads",
		MaxFileSize:      5 << 20, // 5MB
		AllowedMimeTypes: []string{"image/jpeg", "image/png"},
		RandomFilename:   true,
	})

	// 上传处理函数
	uploadHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 检查错误
		if err, ok := r.Context().Value(gulter.UploadErrorContextKey).(error); ok {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		// 获取上传的文件
		files, ok := r.Context().Value(gulter.UploadedFilesContextKey).([]gulter.UploadedFile)
		if !ok || len(files) == 0 {
			http.Error(w, "没有上传文件", http.StatusBadRequest)
			return
		}

		// 返回上传结果
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		for _, file := range files {
			fmt.Fprintf(w, `{"filename": "%s", "size": %d, "mime": "%s"}\n`,
				file.Filename, file.Size, file.MimeType)
		}
	})

	// 文件下载处理
	http.HandleFunc("/download/", func(w http.ResponseWriter, r *http.Request) {
		filename := r.URL.Path[len("/download/"):]
		http.ServeFile(w, r, "./uploads/"+filename)
	})

	// 上传路由
	http.Handle("/upload", uploadMiddleware(uploadHandler))

	// 静态文件服务
	fs := http.FileServer(http.Dir("./static"))
	http.Handle("/", fs)

	log.Println("Server started on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

总结

gulter是一个功能强大且易于使用的Golang文件上传中间件，它提供了：

1. 文件大小限制
2. MIME类型验证
3. 多文件上传支持
4. 随机文件名生成
5. 详细的错误处理
6. 简单的集成方式

通过合理配置，你可以轻松地为你的Golang Web应用添加安全可靠的文件上传功能。