Go语言中将MongoDB文档直接转换为JSON API响应的实用指南

package main

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

    "gopkg.in/mgo.v2" // mgo v1
    "gopkg.in/mgo.v2/bson" // bson v1
)

// 假设我们有一个名为 "mydatabase" 的数据库和一个名为 "mycollection" 的集合

func getDocumentsHandler(w http.ResponseWriter, r *http.Request) {
    session, err := mgo.Dial("mongodb://localhost:27017") // 连接MongoDB
    if err != nil {
        http.Error(w, "Failed to connect to database", http.StatusInternalServerError)
        log.Printf("MongoDB connection error: %v", err)
        return
    }
    defer session.Close()

    collection := session.DB("mydatabase").C("mycollection")

    // 示例：根据名称查询文档
    name := r.URL.Query().Get("name")
    if name == "" {
        http.Error(w, "Missing 'name' query parameter", http.StatusBadRequest)
        return
    }

    var maps []bson.M // 声明一个bson.M切片来存储查询结果
    err = collection.Find(
        bson.M{"name": name}, // 查询条件
    ).All(&maps) // 将所有匹配的文档解组到maps切片中

    if err != nil {
        if err == mgo.ErrNotFound {
            http.Error(w, "Document not found", http.StatusNotFound)
        } else {
            http.Error(w, "Failed to query documents", http.StatusInternalServerError)
            log.Printf("MongoDB query error: %v", err)
        }
        return
    }

    // 设置响应头为JSON
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)

    // 将bson.M切片直接编码为JSON并写入HTTP响应
    encoder := json.NewEncoder(w)
    encoder.SetIndent("", "  ") // 可选：美化JSON输出
    if err := encoder.Encode(maps); err != nil {
        http.Error(w, "Failed to encode JSON response", http.StatusInternalServerError)
        log.Printf("JSON encoding error: %v", err)
        return
    }

    log.Printf("Successfully returned %d documents for name: %s", len(maps), name)
}

func main() {
    // 示例：向MongoDB中插入一些测试数据（如果集合为空）
    session, err := mgo.Dial("mongodb://localhost:27017")
    if err != nil {
        log.Fatalf("Failed to connect to MongoDB for setup: %v", err)
    }
    defer session.Close()

    collection := session.DB("mydatabase").C("mycollection")
    count, _ := collection.Count()
    if count == 0 {
        log.Println("Inserting sample data...")
        err = collection.Insert(
            bson.M{"name": "Alice", "age": 30, "city": "New York"},
            bson.M{"name": "Bob", "age": 25, "city": "London", "interests": []string{"coding", "hiking"}},
            bson.M{"name": "Alice", "age": 32, "city": "Paris", "occupation": "Engineer"},
        )
        if err != nil {
            log.Fatalf("Failed to insert sample data: %v", err)
        }
        log.Println("Sample data inserted.")
    }

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

// ... (接上文代码)

    // 将bson.M切片直接编码为JSON并写入HTTP响应
    encoder := json.NewEncoder(w)
    encoder.SetIndent("", "  ") // 可选：美化JSON输出
    if err := encoder.Encode(maps); err != nil {
        http.Error(w, "Failed to encode JSON response", http.StatusInternalServerError)
        log.Printf("JSON encoding error: %v", err)
        return
    }