MongoDB Go API：高效返回JSON格式文档的实践

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"

    "gopkg.in/mgo.v2"
    "gopkg.in/mgo.v2/bson" // 注意这里使用的是v2版本的mgo/bson
)

// 为了演示，我们假设MongoDB连接已经建立
var session *mgo.Session
var collection *mgo.Collection

func init() {
    // 实际应用中，应从配置加载MongoDB URI并处理连接错误
    var err error
    session, err = mgo.Dial("mongodb://localhost:27017") // 连接到MongoDB
    if err != nil {
        log.Fatalf("Failed to connect to MongoDB: %v", err)
    }
    session.SetMode(mgo.Monotonic, true) // 设置会话模式

    // 获取数据库和集合
    collection = session.DB("mydatabase").C("mycollection")

    // 插入一些示例数据（如果集合为空）
    count, _ := collection.Count()
    if count == 0 {
        collection.Insert(
            bson.M{"name": "Alice", "age": 30, "city": "New York"},
            bson.M{"name": "Bob", "age": 24, "city": "London"},
            bson.M{"name": "Alice", "age": 28, "city": "Paris"},
        )
        log.Println("Inserted sample data.")
    }
}

// GetDocumentsHandler 处理获取MongoDB文档的HTTP请求
func GetDocumentsHandler(w http.ResponseWriter, r *http.Request) {
    // 从请求中获取查询参数，例如 'name'
    name := r.URL.Query().Get("name")
    if name == "" {
        http.Error(w, "Missing 'name' query parameter", http.StatusBadRequest)
        return
    }

    var results []bson.M // 定义一个bson.M切片来存储查询结果

    // 执行查询，将结果直接映射到[]bson.M
    err := collection.Find(bson.M{"name": name}).All(&results)
    if err != nil {
        if err == mgo.ErrNotFound {
            http.Error(w, "No documents found", http.StatusNotFound)
        } else {
            log.Printf("Error querying MongoDB: %v", err)
            http.Error(w, "Internal server error", http.StatusInternalServerError)
        }
        return
    }

    // 将bson.M切片序列化为JSON
    jsonData, err := json.Marshal(results)
    if err != nil {
        log.Printf("Error marshaling JSON: %v", err)
        http.Error(w, "Internal server error", http.StatusInternalServerError)
        return
    }

    // 设置Content-Type头并返回JSON响应
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    _, err = w.Write(jsonData)
    if err != nil {
        log.Printf("Error writing response: %v", err)
    }
}

func main() {
    defer session.Close() // 确保在程序退出时关闭MongoDB会话

    http.HandleFunc("/documents", GetDocumentsHandler)
    port := ":8080"
    fmt.Printf("Server listening on port %s\n", port)
    log.Fatal(http.ListenAndServe(port, nil))
}

[
  {
    "_id": {
      "$oid": "65b9e7b3f9e7c8d7e6f5a4b3"
    },
    "age": 30,
    "city": "New York",
    "name": "Alice"
  },
  {
    "_id": {
      "$oid": "65b9e7b3f9e7c8d7e6f5a4b4"
    },
    "age": 28,
    "city": "Paris",
    "name": "Alice"
  }
]