Go语言mgo驱动：高效将上传文件直接存储到MongoDB GridFS

package main

import (
    "fmt"
    "io/ioutil" // 注意：ioutil 在 Go 1.16+ 已被 io 和 os 包替代，但此处为说明旧代码逻辑
    "net/http"
    "path/filepath"
    "time"

    "gopkg.in/mgo.v2"
    "gopkg.in/mgo.v2/bson"
)

// 假设 mongo_session 已经初始化并连接到 MongoDB
var mongo_session *mgo.Session

func init() {
    // 实际应用中需要配置 MongoDB 连接字符串
    session, err := mgo.Dial("mongodb://localhost:27017")
    if err != nil {
        panic(err)
    }
    session.SetMode(mgo.Monotonic, true)
    mongo_session = session
}

func uploadfilePageHandler(w http.ResponseWriter, req *http.Request) {
    if req.Method != http.MethodPost {
        http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
        return
    }

    // 1. 捕获 multipart 表单文件信息
    file, handler, err := req.FormFile("filename") // "filename" 是表单中文件输入的 name 属性
    if err != nil {
        http.Error(w, fmt.Sprintf("Error getting file: %v", err), http.StatusBadRequest)
        return
    }
    defer file.Close() // 确保文件句柄关闭

    // 2. 将整个文件内容读入内存
    data, err := ioutil.ReadAll(file) // !!! 潜在的内存溢出点 !!!
    if err != nil {
        http.Error(w, fmt.Sprintf("Error reading file into memory: %v", err), http.StatusInternalServerError)
        return
    }

    // 3. 指定 MongoDB 数据库
    my_db := mongo_session.DB("mydatabase")

    // 生成一个唯一的文件名，或使用原始文件名
    unique_filename := fmt.Sprintf("%s_%d%s",
        filepath.Base(handler.Filename),
        time.Now().UnixNano(),
        filepath.Ext(handler.Filename))

    // 4. 在 MongoDB GridFS 实例中创建文件
    my_file, err := my_db.GridFS("fs").Create(unique_filename)
    if err != nil {
        http.Error(w, fmt.Sprintf("Error creating GridFS file: %v", err), http.StatusInternalServerError)
        return
    }
    defer my_file.Close() // 确保 GridFS 文件句柄关闭

    // 5. 将内存中的数据写入 GridFS
    n, err := my_file.Write(data)
    if err != nil {
        http.Error(w, fmt.Sprintf("Error writing to GridFS: %v", err), http.StatusInternalServerError)
        return
    }

    // 6. 关闭文件 (defer my_file.Close() 已处理)

    // 写入日志或返回成功信息
    fmt.Printf("%d bytes written to GridFS instance for file: %s\n", n, unique_filename)
    w.WriteHeader(http.StatusOK)
    w.Write([]byte(fmt.Sprintf("File %s uploaded successfully, %d bytes.", unique_filename, n)))
}

func main() {
    http.HandleFunc("/upload", uploadfilePageHandler)
    fmt.Println("Server starting on :8080")
    err := http.ListenAndServe(":8080", nil)
    if err != nil {
        panic(err)
    }
}

package main

import (
    "fmt"
    "io"
    "net/http"
    "path/filepath"
    "time"

    "gopkg.in/mgo.v2"
    "gopkg.in/mgo.v2/bson"
)

var mongo_session *mgo.Session

func init() {
    session, err := mgo.Dial("mongodb://localhost:27017")
    if err != nil {
        panic(err)
    }
    session.SetMode(mgo.Monotonic, true)
    mongo_session = session
}

func uploadfilePageHandlerOptimized(w http.ResponseWriter, req *http.Request) {
    if req.Method != http.MethodPost {
        http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
        return
    }

    // 1. 捕获 multipart 表单文件信息
    file, handler, err := req.FormFile("filename")
    if err != nil {
        http.Error(w, fmt.Sprintf("Error getting file: %v", err), http.StatusBadRequest)
        return
    }
    defer file.Close() // 确保文件句柄关闭

    // 2. 指定 MongoDB 数据库
    my_db := mongo_session.DB("mydatabase")

    // 生成一个唯一的文件名
    unique_filename := fmt.Sprintf("%s_%d%s",
        filepath.Base(handler.Filename),
        time.Now().UnixNano(),
        filepath.Ext(handler.Filename))

    // 3. 在 MongoDB GridFS 实例中创建文件
    // GridFS.Create 返回的 my_file 实现了 io.Writer 接口
    my_file, err := my_db.GridFS("fs").Create(unique_filename)
    if err != nil {
        http.Error(w, fmt.Sprintf("Error creating GridFS file: %v", err), http.StatusInternalServerError)
        return
    }
    defer my_file.Close() // 确保 GridFS 文件句柄关闭，这会触发文件写入完成

    // 4. 使用 io.Copy 直接将上传文件流式写入 GridFS
    // file (multipart.File) 实现了 io.Reader 接口
    // my_file (*GridFile) 实现了 io.Writer 接口
    n, err := io.Copy(my_file, file) // !!! 关键优化点 !!!
    if err != nil {
        http.Error(w, fmt.Sprintf("Error copying file to GridFS: %v", err), http.StatusInternalServerError)
        return
    }

    // 写入日志或返回成功信息
    fmt.Printf("%d bytes written to GridFS instance for file: %s\n", n, unique_filename)
    w.WriteHeader(http.StatusOK)
    w.Write([]byte(fmt.Sprintf("File %s uploaded successfully, %d bytes.", unique_filename, n)))
}

func main() {
    http.HandleFunc("/upload", uploadfilePageHandlerOptimized)
    fmt.Println("Server starting on :8080 (optimized)")
    err := http.ListenAndServe(":8080", nil)
    if err != nil {
        panic(err)
    }
}