Go语言中处理JSON字符串转换的常见方式

package main

import (
    "encoding/json"
    "fmt"
    "log"
)

type User struct {
    Name  string `json:"name"`
    Age   int    `json:"age"`
    Email string `json:"email,omitempty"`
}

func main() {
    jsonStr := `{"name":"张三","age":25,"email":"zhangsan@example.com"}`

    var user User
    err := json.Unmarshal([]byte(jsonStr), &user)
    if err != nil {
        log.Fatal("JSON 解析错误:", err)
    }

    fmt.Printf("姓名: %s, 年龄: %d, 邮箱: %s\n", user.Name, user.Age, user.Email)
}

func jsonToMap() {
    jsonStr := `{"name":"李四","age":30,"hobbies":["读书","游泳"]}`

    var data map[string]interface{}
    err := json.Unmarshal([]byte(jsonStr), &data)
    if err != nil {
        log.Fatal("JSON 解析错误:", err)
    }

    fmt.Println("姓名:", data["name"])
    fmt.Println("年龄:", data["age"])
    
    // 处理数组类型的值
    if hobbies, ok := data["hobbies"].([]interface{}); ok {
        fmt.Println("爱好:")
        for _, hobby := range hobbies {
            fmt.Println(" -", hobby)
        }
    }
}

func structToJson() {
    user := User{
        Name: "王五",
        Age:  28,
        Email: "wangwu@example.com",
    }

    jsonBytes, err := json.Marshal(user)
    if err != nil {
        log.Fatal("JSON 编码错误:", err)
    }

    jsonStr := string(jsonBytes)
    fmt.Println("JSON 字符串:", jsonStr)
}

func handleRawJSON() {
    jsonStr := `{
        "type": "user",
        "data": {"name":"赵六","age":35},
        "metadata": {"created_at":"2023-01-01"}
    }`

    var rawData map[string]json.RawMessage
    err := json.Unmarshal([]byte(jsonStr), &rawData)
    if err != nil {
        log.Fatal("JSON 解析错误:", err)
    }

    // 根据类型动态解析
    var typeStr string
    json.Unmarshal(rawData["type"], &typeStr)
    
    if typeStr == "user" {
        var user User
        json.Unmarshal(rawData["data"], &user)
        fmt.Println("用户数据:", user)
    }
}

type Address struct {
    City    string `json:"city"`
    Country string `json:"country"`
}

type Person struct {
    Name    string   `json:"name"`
    Age     int      `json:"age"`
    Address Address  `json:"address"`
    Tags    []string `json:"tags"`
}

func complexJSON() {
    jsonStr := `{
        "name": "钱七",
        "age": 40,
        "address": {
            "city": "北京",
            "country": "中国"
        },
        "tags": ["经理", "技术"]
    }`

    var person Person
    err := json.Unmarshal([]byte(jsonStr), &person)
    if err != nil {
        log.Fatal("JSON 解析错误:", err)
    }

    fmt.Printf("姓名: %s\n年龄: %d\n城市: %s\n标签: %v\n",
        person.Name, person.Age, person.Address.City, person.Tags)
}

func streamJSON() {
    jsonStr := `{"name":"孙八","age":45}{"name":"周九","age":50}`
    reader := strings.NewReader(jsonStr)
    decoder := json.NewDecoder(reader)

    for {
        var user User
        if err := decoder.Decode(&user); err != nil {
            if err == io.EOF {
                break
            }
            log.Fatal("解码错误:", err)
        }
        fmt.Printf("流式读取: %+v\n", user)
    }
}

// 美化输出 JSON
func prettyJSON() {
    user := User{Name: "郑十", Age: 55}
    jsonBytes, _ := json.MarshalIndent(user, "", "  ")
    fmt.Println(string(jsonBytes))
}

// 检查字段是否存在
func checkFieldExists() {
    jsonStr := `{"name":"吴十一"}`
    var data map[string]interface{}
    json.Unmarshal([]byte(jsonStr), &data)
    
    if age, exists := data["age"]; exists {
        fmt.Println("年龄:", age)
    } else {
        fmt.Println("年龄字段不存在")
    }
}