Go mgo/bson 字段解组指南：解决大小写不匹配导致的整数类型问题

import (
    "log"
    "gopkg.in/mgo.v2"
    "gopkg.in/mgo.v2/bson"
)

// 假设 subscriptionsCol 是一个 *mgo.Collection 实例

type Subscription struct {
    Id             bson.ObjectId "_id,omitempty"
    Listen         string
    Job            string
    TimeoutSeconds int // 期望从 MongoDB 中获取值
    Data           string
}

func querySubscriptions(subscriptionsCol *mgo.Collection) {
    var subscription Subscription

    // 假设 MongoDB 中存在如下文档：
    // {
    //   "_id": ObjectId("502ed8d84eaead30a1351ea7"),
    //   "job": "partus_test_job_a",
    //   "TimeoutSeconds": 30, // 注意这里是 TitleCase
    //   "listen": "partus.test",
    //   "data": "a=1&b=9"
    // }

    iter := subscriptionsCol.Find(bson.M{"listen": "partus.test"}).Iter()
    for iter.Next(&subscription) {
        log.Printf("Pending job: %s?%s (timeout: %d)\n",
            subscription.Job,
            subscription.Data,
            subscription.TimeoutSeconds) // 此时 subscription.TimeoutSeconds 总是 0
    }
    if err := iter.Close(); err != nil {
        log.Printf("Iterator error: %v\n", err)
    }
}

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

type Subscription struct {
    Id             bson.ObjectId "_id,omitempty"
    Listen         string
    Job            string
    TimeoutSeconds int           "TimeoutSeconds" // 显式指定 BSON 键名为 "TimeoutSeconds"
    Data           string
}

package main

import (
    "fmt"
    "log"
    "time"

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

// Subscription 结构体，TimeoutSeconds 字段使用 BSON 标签进行显式映射
type Subscription struct {
    Id             bson.ObjectId `bson:"_id,omitempty"`
    Listen         string        `bson:"listen"` // 即使默认能匹配，显式指定也是好习惯
    Job            string        `bson:"job"`
    TimeoutSeconds int           `bson:"TimeoutSeconds"` // 关键修正：显式指定 BSON 键名
    Data           string        `bson:"data"`
}

func main() {
    // 连接 MongoDB
    session, err := mgo.Dial("mongodb://localhost:27017")
    if err != nil {
        log.Fatalf("Failed to connect to MongoDB: %v", err)
    }
    defer session.Close()

    // 设置会话模式，确保数据一致性
    session.SetMode(mgo.Monotonic, true)

    // 获取集合
    c := session.DB("testdb").C("subscriptions")

    // 插入测试数据（如果不存在）
    // 注意：这里的字段名与 MongoDB 文档中的实际字段名一致
    testDoc := bson.M{
        "job":            "partus_test_job_a",
        "TimeoutSeconds": 30, // MongoDB 中的字段名
        "listen":         "partus.test",
        "data":           "a=1&b=9",
    }
    // 检查是否已存在，避免重复插入
    count, err := c.Find(bson.M{"listen": "partus.test"}).Count()
    if err != nil {
        log.Fatalf("Failed to count documents: %v", err)
    }
    if count == 0 {
        err = c.Insert(testDoc)
        if err != nil {
            log.Fatalf("Failed to insert test document: %v", err)
        }
        log.Println("Inserted test document.")
    } else {
        log.Println("Test document already exists.")
    }


    // 查询并解组数据
    var subscription Subscription
    iter := c.Find(bson.M{"listen": "partus.test"}).Iter()

    for iter.Next(&subscription) {
        fmt.Printf("成功解组：Job: %s, Data: %s, Timeout: %d 秒\n",
            subscription.Job,
            subscription.Data,
            subscription.TimeoutSeconds) // 现在 TimeoutSeconds 将正确显示 30
    }

    if err := iter.Close(); err != nil {
        log.Fatalf("Iterator error: %v", err)
    }

    fmt.Println("查询完成。")
}