在Go语言GAE Memcache中高效存储与检索Go对象：Codec机制详解

// Object is the Item's value for use with a Codec.
Object interface{}

package main

import (
    "fmt"
    "net/http"

    "google.golang.org/appengine"
    "google.golang.org/appengine/memcache"
)

// MyObject 是我们要存储在Memcache中的自定义结构体
type MyObject struct {
    ID   int
    Name string
    Tags []string
}

func handler(w http.ResponseWriter, r *http.Request) {
    ctx := appengine.NewContext(r)

    // 1. 准备要存储的对象
    inObject := MyObject{
        ID:   1001,
        Name: "示例对象",
        Tags: []string{"Go", "GAE", "Memcache"},
    }

    // 2. 创建memcache.Item
    // 将Go对象赋值给Item的Object字段
    item := &memcache.Item{
        Key:    "my_complex_object_key",
        Object: inObject, // 注意：这里直接赋值Go对象
    }

    // 3. 使用memcache.Gob.Set存储对象
    // memcache.Gob会自动将inObject序列化
    if err := memcache.Gob.Set(ctx, item); err != nil {
        http.Error(w, fmt.Sprintf("Failed to set item: %v", err), http.StatusInternalServerError)
        return
    }
    fmt.Fprintf(w, "Object stored successfully! ID: %d, Name: %s\n", inObject.ID, inObject.Name)

    // 4. 准备一个空变量用于接收检索到的对象
    var outObject MyObject

    // 5. 使用memcache.Gob.Get检索对象
    // memcache.Gob会自动将缓存中的数据反序列化到outObject
    // 注意：outObject必须是指针类型，以便Get方法能修改其内容
    if err := memcache.Gob.Get(ctx, "my_complex_object_key", &outObject); err != nil {
        if err == memcache.ErrCacheMiss {
            fmt.Fprintln(w, "Object not found in cache.")
        } else {
            http.Error(w, fmt.Sprintf("Failed to get item: %v", err), http.StatusInternalServerError)
        }
        return
    }

    // 6. 打印检索到的对象
    fmt.Fprintf(w, "Retrieved object: ID=%d, Name=%s, Tags=%v\n", outObject.ID, outObject.Name, outObject.Tags)
}

func init() {
    http.HandleFunc("/", handler)
}

// ... (之前的MyObject和handler定义)

func jsonHandler(w http.ResponseWriter, r *http.Request) {
    ctx := appengine.NewContext(r)

    inObject := MyObject{
        ID:   2002,
        Name: "JSON示例",
        Tags: []string{"JSON", "Web"},
    }

    item := &memcache.Item{
        Key:    "my_json_object_key",
        Object: inObject,
    }

    // 使用memcache.JSON.Set存储对象
    if err := memcache.JSON.Set(ctx, item); err != nil {
        http.Error(w, fmt.Sprintf("Failed to set item with JSON: %v", err), http.StatusInternalServerError)
        return
    }
    fmt.Fprintf(w, "JSON Object stored successfully! ID: %d\n", inObject.ID)

    var outObject MyObject
    // 使用memcache.JSON.Get检索对象
    if err := memcache.JSON.Get(ctx, "my_json_object_key", &outObject); err != nil {
        if err == memcache.ErrCacheMiss {
            fmt.Fprintln(w, "JSON Object not found in cache.")
        } else {
            http.Error(w, fmt.Sprintf("Failed to get item with JSON: %v", err), http.StatusInternalServerError)
        }
        return
    }

    fmt.Fprintf(w, "Retrieved JSON object: ID=%d, Name=%s, Tags=%v\n", outObject.ID, outObject.Name, outObject.Tags)
}

func init() {
    http.HandleFunc("/", handler)         // Gob example
    http.HandleFunc("/json", jsonHandler) // JSON example
}