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Go语言的Json管理模式

在Go语言中Json管理是一个微不足道的问题，但是也会出现但少数避免的问题:

如何为字段提供默认值？
如何使一个字段可选?
如何避免使用某些字段的默认值 (如︰用户 id)？
如何防止指针维护的问题
如何验证？

下面一些示例演示如将一个Struct解析成一个Json文档

Go语言的Json管理模式

我们来看一个在我们在日常开发中常用的一个Model，a User, a Scene, a Parcel，Models能够Marshaled Json，同样Json也能Unmarshaled为Models。在所有程序中,我们需要验证传入的Json。

当我们要把一个Json解析成Model的时候, 我们利用结构标记来表示字段名称，比如我们可以用”omitempty”,来告诉程序我们是否忽略这个字段当它的值为空的时候。

type Model struct {   UserIduint `json:"user_id"`   Addressstring `json:"address,omitempty"` // if empty, don't encode it at all }

默认字段

ProductCountuint // required, but zero is a safe default

自定义默认字段

FavoriteColorstring // a default is ok, but we don't want the empty string

可选字段

Address *string // not required, but we still want to validate it if it's there

取消引用的必填的字段

type Request struct {   UserId *uint // this is a Required Non-Default Field, so it needs a pointer }   type Model struct {   UserIduint // but it's not optional, so we don't want the pointer in the model }

简单验证

UserId *uint `validate:"nonzero"` AgeUint `validate:"min=18"`

Pattern 1

Features: Default Fields , Easy Validation

// model type User struct {     Namestring    `json:"name"    validate:"nonzero"`     Ageuint      `json:"age"    validate:"min=1"`     Addressstring `json:"address" validate:"nonzero"` }   // unmarshalling var userUser if err := json.NewDecoder(jsonByteSlice).Decode(&user); err != nil {...}   // marshalling if jsonByteSlice, err := json.Marshal(object); err != nil {...}   // validation if errs := validator.Validate(user); errs != nil {...}

Pattern 2

Features: Default Fields , Optional Fields , Required Non Default Fields

// model type User struct {     Name          *string `json:"name"`              // required, but no defaults     Age           *uint  `json:"age,omitempty"`    // optional     Address       *string `json:"address,omitempty"` // optional     FavoriteColorstring  `json:"favoriteColor"`    // required, uses defaults }   // unmarshalling var userUser if err := json.NewDecoder(jsonByteSlice).Decode(&user); err != nil {...}   // marshalling if jsonByteSlice, err := json.Marshal(object); err != nil {...}   // validation funcValidate(userUser) {     // default - validate value     // optional - if non nil, validate value     // required non default - validate not nil, then validate value }

Pattern 3

Features: Default Fields , Optional Fields , Required Non Default Fields , Easy Validation

UserId *uint `validate:"nonzero,min=100"`

// model type User struct {     Name          *string `json:"name"              validate:"nonzero,min=1"` // required, but no defaults     Age           *uint  `json:"age,omitempty"    validate:"min=1"`        // optional     Address       *string `json:"address,omitempty" validate:"min=1"`        // optional     FavoriteColorstring  `json:"favoriteColor"`                              // required, uses defaults }   // unmarshalling var userUser if err := json.NewDecoder(jsonByteSlice).Decode(&user); err != nil {..}   // marshalling if jsonByteSlice, err := json.Marshal(object); err != nil {...}   // validation if errs := validator.Validate(user); errs != nil {...}

Pattern 4

Features: Default Fields , Required Non Default Fields , Easy Validation , Custom Default Fields , Dereferenced Required Fields

// post request type UserPostRequest struct {     Name               *string `json:"name" validate:"nonzero"` // required, but no defaults     Age                *uint  `json:"age"`                    // optional     Address            *string `json:"address"`                // optional     FavoriteInstrumentstring  `json:"favoriteInstrument"`      // required, uses defaults     FavoriteColor      *string `json:"favoriteColor"`          // required, uses custom defaults }   // model type User struct {     Name              string  `json:"name" validate:"nonzero"`            // required     Age                *uint  `json:"age,omitempty" validate:"min=1"`    // optional     Address            *string `json:"address,omitempty" validate:"min=1"` // optional     FavoriteInstrumentstring  `json:"favoriteInstrument"`                // required     FavoriteColor      string  `json:"favoriteColor" validate:"nonzero"`  // required }   // unmarshalling var postRequestUserPostRequest if err := json.NewDecoder(jsonByteSlice).Decode(&postRequest); err != nil {..} if errs := validator.Validate(postRequest); errs != nil {...}   user.Name = *postRequest.Name user.Age = postRequest.Age user.Address = postRequest.Address user.FavoriteInstrument = postRequest.FavoriteInstrument user.FavoriteColor = "blue" if postRequest.FavoriteColor != nil {   user.FavoriteColor = *postRequest.FavoriteColor } if errs := validator.Validate(user); errs != nil {...}   // marshalling if jsonByteSlice, err := marshal(object); err != nil {...}   // validation if errs := validator.Validate(user); errs != nil {...}

参考文献： http://brandonokert.com/2016/04/18/Json-Management-Patterns-In-Go/

Go语言的Json管理模式

原文 https://xiequan.info/go语言的json管理模式/

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