Go语言第十六课 JSON

type类型转JSON string（编码）

Go核心库已经对JSON有比较好的支持，编码部分是由核心库encoding/json支持的。

package main

import (
	"encoding/json"
	"fmt"
)

type persion struct {
	Name    string
	Age     int
	Gender  string
	School  string
	Married bool
}

func main() {
	var yong persion
	yong.Age = 26
	yong.Name = "Yong.Yu"
	yong.Gender = "M"
	yong.School = "USC"
	yong.Married = true
	j_yong, err := json.Marshal(yong)
	if err == nil {
		fmt.Printf("%s\n", j_yong)
	}
}

结果：

{"Name":"Yong.Yu","Age":26,"Gender":"M","School":"USC","Married":true}

* 注意：由于编码实际上用到的是反射，所以类型里需要编码的属性必须是可导出的，也就是必须以大写开头。如上面的例子，如果将persion类型的Name属性改成小写name，再编码结果为：{"Age":26,"Gender":"M","School":"USC","Married":true}。这是因为name不可导出，自然就无法编码。

默认编码出来的key是属性的属性名，但是这一点可以更改。

package main

import (
	"encoding/json"
	"fmt"
)

type persion struct {
	Name    string
	Age     int
	Gender  string
	School  string `json:"school-name"`
	Married bool
}

func main() {
	var yong persion
	yong.Age = 26
	yong.Name = "Yong.Yu"
	yong.Gender = "M"
	yong.School = "USC"
	yong.Married = true
	j_yong, err := json.Marshal(yong)
	if err == nil {
		fmt.Printf("%s\n", j_yong)
	}
}

结果：

{"Name":"Yong.Yu","Age":26,"Gender":"M","school-name":"USC","Married":true}

显然，如果没有对某个属性赋值，这个属性将被赋默认零值。这个零值也会出现在编码之后的JSON中。但是这一点可以更改，借助omitempty，JSON内将不包含那些零值的属性。

package main

import (
	"encoding/json"
	"fmt"
)

type persion struct {
	Name    string
	Age     int    `json:"age,omitempty"`
	Gender  string
	School  string `json:"school-name"`
	Married bool
}

func main() {
	var yong persion
	yong.Age = 26
	yong.Name = "Yong.Yu"
	yong.Gender = "M"
	yong.School = "USC"
	yong.Married = true
	j_yong, err := json.Marshal(yong)
	if err == nil {
		fmt.Printf("%s\n", j_yong)
	}
	//-------------------------------------
	var yong1 persion
	yong1.Name = "Yong1.Yu"
	yong1.Gender = "M"
	yong1.School = "USC"
	yong1.Married = true
	j_yong, err = json.Marshal(yong1)
	if err == nil {
		fmt.Printf("%s\n", j_yong)
	}
}

结果：

{"Name":"Yong.Yu","age":26,"Gender":"M","school-name":"USC","Married":true}

{"Name":"Yong1.Yu","Gender":"M","school-name":"USC","Married":true}

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解码操作刚好相反

package main

import (
	"encoding/json"
	"fmt"
)

type persion struct {
	Name    string
	Age     int    `json:"age,omitempty"`
	Gender  string
	School  string `json:"school-name"`
	Married bool
}

func main() {
	var yong persion
	yong.Age = 26
	yong.Name = "Yong.Yu"
	yong.Gender = "M"
	yong.School = "USC"
	yong.Married = true
	j_yong, err := json.Marshal(yong)
	if err == nil {
		fmt.Printf("%s\n", j_yong)
	}
	//-------------------------------------
	var p_yong *persion = new(persion)
	json.Unmarshal([]byte(j_yong), p_yong)
	fmt.Println(p_yong.Name)
	fmt.Println(p_yong.Age)
}

结果

{"Name":"Yong.Yu","age":26,"Gender":"M","school-name":"USC","Married":true}
Yong.Yu
26