GAE Go 中处理 URLFetch POST 请求的正确姿势

package myapp

import (
    "bytes"
    "context"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "log"
    "net/http"

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

// 定义一个示例数据结构用于POST请求体
type RequestPayload struct {
    Name  string `json:"name"`
    Value string `json:"value"`
}

// 定义一个示例数据结构用于响应体
type ResponsePayload struct {
    Status  string `json:"status"`
    Message string `json:"message"`
}

// handlePostRequest 是一个处理HTTP POST请求的示例处理器
func handlePostRequest(w http.ResponseWriter, r *http.Request) {
    // 1. 获取应用上下文
    ctx := appengine.NewContext(r)

    // 2. 创建 urlfetch 客户端
    // 这个客户端会自动使用 GAE 的 urlfetch 服务
    client := urlfetch.Client(ctx)

    // 准备 POST 请求体数据
    payload := RequestPayload{
        Name:  "TestUser",
        Value: "TestData123",
    }
    jsonPayload, err := json.Marshal(payload)
    if err != nil {
        log.Errorf(ctx, "Failed to marshal JSON payload: %v", err)
        http.Error(w, "Internal Server Error", http.StatusInternalServerError)
        return
    }

    targetURL := "https://api.example.com/data" // 替换为你的目标POST URL

    // 方法一：使用 http.Client.Post 方法发送 POST 请求
    resp, err := client.Post(targetURL, "application/json", bytes.NewBuffer(jsonPayload))
    if err != nil {
        log.Errorf(ctx, "Failed to send POST request using client.Post: %v", err)
        http.Error(w, "Failed to connect to external service", http.StatusBadGateway)
        return
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK {
        log.Errorf(ctx, "Received non-OK status code from client.Post: %d", resp.StatusCode)
        http.Error(w, fmt.Sprintf("External service returned error: %d", resp.StatusCode), http.StatusBadGateway)
        return
    }

    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        log.Errorf(ctx, "Failed to read response body from client.Post: %v", err)
        http.Error(w, "Internal Server Error", http.StatusInternalServerError)
        return
    }

    var responsePayload ResponsePayload
    if err := json.Unmarshal(body, &responsePayload); err != nil {
        log.Errorf(ctx, "Failed to unmarshal response body from client.Post: %v", err)
        http.Error(w, "Internal Server Error", http.StatusInternalServerError)
        return
    }

    fmt.Fprintf(w, "POST request successful! Status: %s, Message: %s\n", responsePayload.Status, responsePayload.Message)
    log.Infof(ctx, "Successfully processed POST request via client.Post. Response: %+v", responsePayload)

    // 方法二：使用 http.Client.Do 方法发送更灵活的 POST 请求 (推荐，因为它更通用)
    // req, err := http.NewRequest("POST", targetURL, bytes.NewBuffer(jsonPayload))
    // if err != nil {
    //  log.Errorf(ctx, "Failed to create new POST request: %v", err)
    //  http.Error(w, "Internal Server Error", http.StatusInternalServerError)
    //  return
    // }
    // req.Header.Set("Content-Type", "application/json")
    // req.Header.Set("Authorization", "Bearer your_token_here") // 添加自定义头部

    // resp, err = client.Do(req)
    // if err != nil {
    //  log.Errorf(ctx, "Failed to send POST request using client.Do: %v", err)
    //  http.Error(w, "Failed to connect to external service", http.StatusBadGateway)
    //  return
    // }
    // defer resp.Body.Close()

    // // ... 后续处理与方法一类似 ...
    // fmt.Fprintf(w, "POST request successful via client.Do! Status: %s, Message: %s\n", responsePayload.Status, responsePayload.Message)
}

func init() {
    http.HandleFunc("/post-data", handlePostRequest)
}