go 文件服务(读取须权限)

package Network

import (
    "encoding/base64"
    "encoding/json"
    "net/http"
    "os"
    "strings"
    "time"
    "token"
)

func getFile(w http.ResponseWriter, req *http.Request) {
    var (
        code     int         = Success
        msg      string      = ""
        result   interface{} = nil
        httpCode int         = http.StatusOK
    )
    defer func() {
        w.WriteHeader(httpCode)
        if httpCode != http.StatusOK {
            writeHTTPResult(w, code, msg, result)
        }
    }()
    Token := req.FormValue("token")
    user, ok := token.GetUser(Token)
    if !ok {
        httpCode = http.StatusForbidden
        code = errNoPermission
        msg = "token 无效"
        return
    }

    httpCode, fileInfo, base64FileName := Decode(req)

    if user.ID == fileInfo.ReceiverID || user.ID == fileInfo.SenderID {
        httpCode, code, msg = WriteFile(w, req, fileInfo, base64FileName)
        return
    }

    code, msg = IsGroupID(fileInfo.ReceiverID)
    if code != Success {
        httpCode = http.StatusForbidden
        if code == errInvalidID {
            code = errNoPermission
            msg = "you have no permission to get this file"
        }
        return
    }

    code, msg = IsGroupMember(user.ID, fileInfo.ReceiverID)
    if code != Success {
        httpCode = http.StatusForbidden
        if code == errInvalidID {
            code = errNoPermission
            msg = "you have no permission to get this file"
        }
        return
    }

    httpCode, code, msg = WriteFile(w, req, fileInfo, base64FileName)
    return

}
func WriteFile(w http.ResponseWriter, req *http.Request, fileInfo *FileInfo, base64FileName string) (httpCode int, code int, msg string) {
    file, err := os.Open(publicFileDir + "/" + fileInfo.FileType + "/" + base64FileName)
    if err != nil {
        httpCode = http.StatusNotFound
        code = errFileNotFound
        msg = err.Error()
        return
    }
    defer file.Close()
    w.Header().Set("Filename", fileInfo.FileName)
    http.ServeContent(w, req, fileInfo.FileName, time.Time{}, file)
    return http.StatusOK, Success, ""
}

func Decode(req *http.Request) (httpCode int, fileInfo *FileInfo, base64FileName string) {
    fileInfo = new(FileInfo)
    URL := strings.Split(req.URL.Path, "/")
    if len(URL) == 0 {
        return http.StatusNotFound, nil, base64FileName
    }
    base64FileName = URL[len(URL)-1]
    fileName, err := base64.StdEncoding.DecodeString(base64FileName)
    if err != nil {
        return http.StatusBadRequest, nil, base64FileName
    }
    err = json.Unmarshal(fileName, fileInfo)
    if err != nil {
        return http.StatusForbidden, nil, base64FileName
    }
    return http.StatusOK, fileInfo, base64FileName
}

func getFile(uri string, fileName string) error {
    resp, err := http.Get(uri)
    if err != nil {
        return err
    }
    defer resp.Body.Close()
    if resp.StatusCode != http.StatusOK {
        body, err := ioutil.ReadAll(resp.Body)
        if err != nil {
            return err
        }
        return errors.New("statusCode:" + fmt.Sprint(resp.StatusCode) + "
" + string(body))
    }
    if fileName == "" {
        if resp.Header["Filename"] != nil {
            fileName = resp.Header["Filename"][0]
        } else {
            fileName = "notFound"
        }
    }
    icon, err := os.Create(fileName)
    if err != nil {
        return err
    }
    _, err = io.Copy(icon, resp.Body)
    if err != nil {
        return err
    }
    logs.Print(resp.Header)
    return nil
}

这里由于http response的body完全是文件的二进制流，所以Filename要么是前端定义，要么是后端通过header返回

文件的url是一个base64编码的字符串，包含验证读取权限相关的所有信息和源文件名(服务器存文件时用的是base64编码作为文件名)