转自:https://blog.csdn.net/zxy_666/article/details/80173288
作者:滢光点点 
来源:CSDN 
原文:https://blog.csdn.net/zxy_666/article/details/80173288 
 

简介

Json(Javascript Object Nanotation)是一种数据交换格式,常用于前后端数据传输。任意一端将数据转换成json 字符串,另一端再将该字符串解析成相应的数据结构,如string类型,strcut对象等。

go语言本身为我们提供了json的工具包”encoding/json”。 
更多的使用方式,可以参考:https://studygolang.com/articles/6742

 

实现

Json Marshal:将数据编码成json字符串

看一个简单的例子

type Stu struct {
    Name  string `json:"name"`
    Age   int
    HIgh  bool
    sex   string
    Class *Class `json:"class"`
}

type Class struct {
    Name  string
    Grade int
}

func main() {
    //实例化一个数据结构,用于生成json字符串
    stu := Stu{
        Name: "张三",
        Age:  18,
        HIgh: true,
        sex:  "男",
    }

    //指针变量
    cla := new(Class)
    cla.Name = "1班"
    cla.Grade = 3
    stu.Class=cla

    //Marshal失败时err!=nil
    jsonStu, err := json.Marshal(stu)
    if err != nil {
        fmt.Println("生成json字符串错误")
    }

    //jsonStu是[]byte类型,转化成string类型便于查看
    fmt.Println(string(jsonStu))
}

结果:

{"name":"张三","Age":18,"HIgh":true,"class":{"Name":"1班","Grade":3}}

从结果中可以看出

  • 只要是可导出成员(变量首字母大写),都可以转成json。因成员变量sex是不可导出的,故无法转成json。
  • 如果变量打上了json标签,如Name旁边的 `json:"name"` ,那么转化成的json key就用该标签“name”,否则取变量名作为key,如“Age”,“HIgh”。
  • bool类型也是可以直接转换为json的value值。Channel, complex 以及函数不能被编码json字符串。当然,循环的数据结构也不行,它会导致marshal陷入死循环。
  • 指针变量,编码时自动转换为它所指向的值,如cla变量。

    (当然,不传指针,Stu struct的成员Class如果换成Class struct类型,效果也是一模一样的。只不过指针更快,且能节省内存空间。)

  • 最后,强调一句:json编码成字符串后就是纯粹的字符串了。

注意:上面的成员变量都是已知的类型,只能接收指定的类型,比如string类型的Name只能赋值string类型的数据。 
但有时为了通用性,或使代码简洁,我们希望有一种类型可以接受各种类型的数据,并进行json编码。这就用到了interface{}类型。

-------------------------------------------------------------------------------------------------------------------------------------------------------------------

前言: 
interface{}类型其实是个空接口,即没有方法的接口。go的每一种类型都实现了该接口。因此,任何其他类型的数据都可以赋值给interface{}类型

type Stu struct {
    Name  interface{} `json:"name"`
    Age   interface{}
    HIgh  interface{}
    sex   interface{}
    Class interface{} `json:"class"`
}

type Class struct {
    Name  string
    Grade int
}

func main() {
    //与前面的例子一样
    ......
}

结果:

{"name":"张三","Age":18,"HIgh":true,"class":{"Name":"1班","Grade":3}}

从结果中可以看出,无论是string,int,bool,还是指针类型等,都可赋值给interface{}类型,且正常编码,效果与前面的例子一样。

GitHub 加速计划 / js / json
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适用于现代 C++ 的 JSON。
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f06604fc * :page_facing_up: bump the copyright years Signed-off-by: Niels Lohmann <mail@nlohmann.me> * :page_facing_up: bump the copyright years Signed-off-by: Niels Lohmann <mail@nlohmann.me> * :page_facing_up: bump the copyright years Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com> 20 天前
d23291ba * add a ci step for Json_Diagnostic_Positions Signed-off-by: Harinath Nampally <harinath922@gmail.com> * Update ci.cmake to address review comments Signed-off-by: Harinath Nampally <harinath922@gmail.com> * address review comment Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix typo in the comment Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix typos in ci.cmake Signed-off-by: Harinath Nampally <harinath922@gmail.com> * invoke the new ci step from ubuntu.yml Signed-off-by: Harinath Nampally <harinath922@gmail.com> * issue4561 - use diagnostic positions for exceptions Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci_test_documentation check Signed-off-by: Harinath Nampally <harinath922@gmail.com> * address review comments Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci check failures for unit-diagnostic-postions.cpp Signed-off-by: Harinath Nampally <harinath922@gmail.com> * improvements based on review comments Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix const correctness string Signed-off-by: Harinath Nampally <harinath922@gmail.com> * further refinements based on reviews Signed-off-by: Harinath Nampally <harinath922@gmail.com> * add one more test case for full coverage Signed-off-by: Harinath Nampally <harinath922@gmail.com> * ci check fix - add const Signed-off-by: Harinath Nampally <harinath922@gmail.com> * add unit tests for json_diagnostic_postions only Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci_test_diagnostics Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci_test_build_documentation check Signed-off-by: Harinath Nampally <harinath922@gmail.com> --------- Signed-off-by: Harinath Nampally <harinath922@gmail.com> 21 天前
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