Golang从接口端点获取图片表单数据时遇到问题

在Go中处理文件上传时，你需要正确解析multipart/form-data请求。以下是处理UIkit上传组件的示例代码：

package main

import (
    "fmt"
    "io"
    "net/http"
    "os"
)

func uploadHandler(w http.ResponseWriter, r *http.Request) {
    // 设置最大文件大小（例如10MB）
    r.ParseMultipartForm(10 << 20)
    
    // 获取文件头
    file, handler, err := r.FormFile("this_is_the_file_i_want")
    if err != nil {
        fmt.Println("Error retrieving the file:", err)
        http.Error(w, "Error retrieving file", http.StatusBadRequest)
        return
    }
    defer file.Close()
    
    // 打印文件信息
    fmt.Printf("Uploaded File: %+v\n", handler.Filename)
    fmt.Printf("File Size: %+v\n", handler.Size)
    fmt.Printf("MIME Header: %+v\n", handler.Header)
    
    // 创建目标文件
    dst, err := os.Create("/tmp/" + handler.Filename)
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    defer dst.Close()
    
    // 复制文件内容
    if _, err := io.Copy(dst, file); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    
    fmt.Fprintf(w, "Successfully uploaded file")
}

// 处理多个文件上传
func uploadMultipleHandler(w http.ResponseWriter, r *http.Request) {
    // 设置最大文件大小
    r.ParseMultipartForm(10 << 20)
    
    // 获取multipart reader
    reader, err := r.MultipartReader()
    if err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }
    
    // 遍历所有part
    for {
        part, err := reader.NextPart()
        if err == io.EOF {
            break
        }
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        
        // 检查是否是文件字段
        if part.FileName() != "" {
            fmt.Printf("Fieldname: %s, Filename: %s\n", part.FormName(), part.FileName())
            
            // 保存文件
            dst, err := os.Create("/tmp/" + part.FileName())
            if err != nil {
                http.Error(w, err.Error(), http.StatusInternalServerError)
                return
            }
            
            if _, err := io.Copy(dst, part); err != nil {
                dst.Close()
                http.Error(w, err.Error(), http.StatusInternalServerError)
                return
            }
            dst.Close()
        }
    }
    
    fmt.Fprintf(w, "Successfully uploaded files")
}

func main() {
    http.HandleFunc("/upload", uploadHandler)
    http.HandleFunc("/upload-multiple", uploadMultipleHandler)
    http.ListenAndServe(":8080", nil)
}

如果你的前端使用multiple属性上传多个文件，可以使用这个替代方案：

func uploadMultipleFiles(w http.ResponseWriter, r *http.Request) {
    // 解析multipart表单
    err := r.ParseMultipartForm(10 << 20) // 10MB
    if err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }
    
    // 获取所有文件
    files := r.MultipartForm.File["this_is_the_file_i_want"]
    
    for _, fileHeader := range files {
        // 打开文件
        file, err := fileHeader.Open()
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        defer file.Close()
        
        // 创建目标文件
        dst, err := os.Create("/tmp/" + fileHeader.Filename)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        defer dst.Close()
        
        // 复制文件内容
        if _, err := io.Copy(dst, file); err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
    }
    
    fmt.Fprintf(w, "Successfully uploaded %d files", len(files))
}

调试时可以使用这个函数查看所有接收到的数据：

func debugUpload(w http.ResponseWriter, r *http.Request) {
    // 打印所有表单字段
    r.ParseMultipartForm(10 << 20)
    
    fmt.Println("Form values:")
    for k, v := range r.Form {
        fmt.Printf("%s: %v\n", k, v)
    }
    
    fmt.Println("\nMultipart form files:")
    for k, v := range r.MultipartForm.File {
        fmt.Printf("%s: %v files\n", k, len(v))
        for _, f := range v {
            fmt.Printf("  - %s (size: %d)\n", f.Filename, f.Size)
        }
    }
    
    fmt.Println("\nPost form values:")
    for k, v := range r.PostForm {
        fmt.Printf("%s: %v\n", k, v)
    }
}

确保你的HTML表单设置了正确的enctype：

<form action="/upload" method="POST" enctype="multipart/form-data">
    <!-- 你的文件输入字段 -->
</form>