Google App Engine Go Datastore 中的最大数据类型

package main

import (
    "fmt"
    "google.golang.org/appengine/datastore"
    "context"
)

type MyEntity struct {
    LargeData []byte
}

func storeData(ctx context.Context, key *datastore.Key, data string) error {
    entity := MyEntity{
        LargeData: []byte(data),
    }
    _, err := datastore.Put(ctx, key, &entity)
    return err
}

func retrieveData(ctx context.Context, key *datastore.Key) (string, error) {
    var entity MyEntity
    err := datastore.Get(ctx, key, &entity)
    if err != nil {
        return "", err
    }
    return string(entity.LargeData), nil
}

func main() {
    // 假设已经获取了 context 和 datastore key
    // 这里只是示例，需要替换成实际的 context 和 key
    ctx := context.Background()
    key := datastore.NewKey(ctx, "MyEntity", "uniqueID", 0, nil)

    largeString := "This is a very long string that exceeds the 500 character limit.  It demonstrates how to store larger text in Google App Engine Datastore using the []byte type.  This approach allows you to store up to 1MB of data per property. This is a very long string that exceeds the 500 character limit.  It demonstrates how to store larger text in Google App Engine Datastore using the []byte type.  This approach allows you to store up to 1MB of data per property."

    err := storeData(ctx, key, largeString)
    if err != nil {
        fmt.Println("Error storing data:", err)
        return
    }

    retrievedString, err := retrieveData(ctx, key)
    if err != nil {
        fmt.Println("Error retrieving data:", err)
        return
    }

    fmt.Println("Retrieved data:", retrievedString)
}

// 获取上传 URL
uploadURL, err := blobstore.CreateUploadURL(c, "/upload", nil)

// 上传处理程序（/upload）
func uploadHandler(w http.ResponseWriter, r *http.Request) {
    blobs := blobstore.Files(r)
    file := blobs["file"] // "file" 是 HTML 表单中文件上传字段的名称

    if len(file) > 0 {
        blobKey := file[0].BlobKey
        // 将 blobKey 存储到 Datastore
        // ...
    }
}

// 下载处理程序
func downloadHandler(w http.ResponseWriter, r *http.Request) {
    blobKey := appengine.BlobKey(r.FormValue("blobKey"))
    blobstore.Send(w, blobKey)
}