golang json 编码解码

Posted 2020-11-02 冯持

golang  "encoding/json"包实现了json对象的编解码

一、编码

func Marshal(v interface{}) ([]byte, error)

Marshal函数使用下面的基于类型的默认编码格式：

布尔类型编码为json布尔类型。

浮点数、整数和Number类型的值编码为json数字类型。

字符串编码为json字符串。角括号"<"和">"会转义为"\u003c"和"\u003e"以避免某些浏览器吧json输出错误理解为html。基于同样的原因，"&"转义为"\u0026"。

数组和切片类型的值编码为json数组，但[]byte编码为base64编码字符串，nil切片编码为null。

结构体的值编码为json对象。每一个导出字段变成该对象的一个成员

Example:

 1 package main
 2 
 3 import(
 4     "fmt"
 5     "encoding/json"
 6 )
 7 func main() {
 8     type User struct{
 9         Name string
10         Age int
11     }
12     user := User{
13         Name:"tom",
14         Age:3,
15     }
16     b, err := json.Marshal(user)
17     if err != nil {
18         fmt.Println("json Marshal fail:", err)
19     }
20     fmt.Println(string(b))
21 }

Output:

{"Name":"tom","Age":3}

 

1 不可导出字段，不会被编码

Example:

type User struct{
        Name string
        age int
    }
    user := User{
        Name:"tom",
        age:3,
    }
    b, _ := json.Marshal(user)
    fmt.Println(string(b))

Output:

{"Name":"tom"}

 

2 可通过结构体标签，改变编码的json对象

Example:

type User struct{
        Name string `json:"name"`
        Age int     `json:"ageeeeeeeeeeeeeeeeee"`
    }
    user := User{
        Name:"tom",
        Age:3,
    }
    b, _ := json.Marshal(user)
    fmt.Println(string(b))

Output:

{"name":"tom","ageeeeeeeeeeeeeeeeee":3}

 

3 复杂结构体编码：

　　 指针编码为它指向的值

　　 切片编码为数组

　　 结构体的值编码为json对象

Example:

    // 复杂结构体编码
    //基本类型指针，结构体指针,切片，切片指针，
    type Contact struct {
        Addr string
        Phone string
    }

    type User struct {
        Name string
        Age *int
        C1 *Contact
        C2 []Contact
        C3 []*Contact
    }
    age := 20
    c1 := Contact{"北京","12345"}
    cArr := [...]Contact{Contact{"北京","11111"},Contact{"深圳","22222"},Contact{"上海","33333"}}
    c2 := cArr[:2]
    c3 := make([]*Contact,0)
    c3 = append(c3, &cArr[0])
    c3 = append(c3, &cArr[1])

    user := User{
        Name:    "Tom",
        Age:     &age,
        C1:      &c1,
        C2:      c2,
        C3:      c3,
    }
    fmt.Printf("struct: %v\n", user)
    b, _ := json.Marshal(user)
    fmt.Println("json: ", string(b))

 

Output:

struct: {Tom 0xc04204a1c8 0xc042044580 [{北京 11111} {深圳 22222}] [0xc042086000 0xc042086020]}
json:  {"Name":"Tom","Age":20,"C1":{"Addr":"北京","Phone":"12345"},"C2":[{"Addr":"北京","Phone":"11111"},{"Addr":"深圳","Phone":"22222"}],"C3":[{"Addr":"北京","Phone":"11111"},{"Addr":"深圳","Phone":"22222"}]}

 

二、解码

 

func Unmarshal(data []byte, v interface{}) error

 

Example

//json解码 测试
    type Contact struct {
        Addr string
        Phone string
    }

    type User struct {
        Name string
        Age *int
        C1 *Contact
        C2 []Contact
        C3 []*Contact
    }

    user := User{}
    j := `{
                "Name": "Tom",
                "Age": 20,
                "C1": {
                    "Addr": "北京",
                    "Phone": "12345"
                },
                "C2": [{
                    "Addr": "北京",
                    "Phone": "11111"
                }, {
                    "Addr": "深圳",
                    "Phone": "22222"
                }],
                "C3": [{
                    "Addr": "北京",
                    "Phone": "11111"
                }, {
                    "Addr": "深圳",
                    "Phone": "22222"
                }]
            }`
    err := json.Unmarshal([]byte(j), &user)
    if err != nil {
        fmt.Println("json Unmarshal fail!")
    }
    fmt.Printf("%v\n", user)
    fmt.Println(*user.Age)
    fmt.Println(*user.C1)
    fmt.Println(*user.C3[0])

 

Output

{Tom 0xc04204a3a8 0xc0420447a0 [{北京 11111} {深圳 22222}] [0xc042044860 0xc042044880]}
20
{北京 12345}
{北京 11111}

 

参考: Go语言标准库文档中文版