介绍一个golang struct 校验工具【qvalid】

这个库是去年写的，主要用于结构体的校验。
比如字符串长度、数值大小、oneof，以及字符串的一些常见属性（email/url/ip）等。
项目的地址：https://github.com/miaomiao3/qvalid
因为不想用一些现成但很臃肿的库如govalidator，就自己写了一个，写的时候希望语法尽可能精简，借用了mongodb的一些约束，比如lt/lte gt/gte概念，来约束字符串的长度或者数值的值大小。由于开发的时候是针对某些特定场合用的，所以完备性是有待提高的（主要的代码大概花了半天那样子，就是说可能有bug哈，如果有兴趣可以提issue和pr）。但是基本功能是没问题的。
下面内容摘自repo的readme，懒得翻成中文了，将就看一下吧。

qvalid

powerful tool to validate struct’s exported fields

Features

• validate field value of numbers(int/uint/float…)
• validate field length of string/array/slice/map
• support in check
• when a field is slice and its element is struct/struct_pointer, qvalid auto validate this struct related element
• when a field is string, support attribute check. e.g. email/ip/email…
• pretty field output msg, use json tag first as field name

Install

go get -u github.com/miaomiao3/qvalid

Syntax

• As for bound limit, it means length of string/array/slice/map, and value of numbers(int/uint/float…)
• If ‘in’ was set, do not set bound limit
• , and = reserved
• [ and ] reserved except of in constraint

constraint description

attr is available as below

const (
	StringTypeEmail        = "email"
	StringTypeAlpha        = "alpha"
	StringTypeUpperAlpha   = "upper_alpha"
	StringTypeLowerAlpha   = "lower_alpha"
	StringTypeAlphaNumeric = "alpha_numeric"
	StringTypeNumeric      = "numeric"
	StringTypeInt          = "int"
	StringTypeFloat        = "float"
	StringTypeHex          = "hex"
	StringTypeAscii        = "ascii"
	StringTypeVisibleAscii = "visible_ascii"
	StringTypeBytes        = "bytes"
	StringTypeBase64       = "base64"
	StringTypeDNS          = "dns"
	StringTypeVersion      = "version"
	StringTypeIp           = "ip"
	StringTypePort         = "port"
	StringTypeURL          = "url"
)

Examples

First, define some struct:

type Dog struct {
	Name      string            `valid:"in=[rose,tulip]" json:"name"`
	Color     string            `valid:"lt=5, gte=3" json:"color"`
	Weight    float64           `valid:"lt=100, gte=10" json:"weight"`
	Clothes   int               `valid:"in=[1,3,5]" json:"clothes"`
	NickNames []string          `valid:"lt=5, gt=1"`
	Relations map[string]string `valid:"lt=5, gt=1"`
	Email     string            `valid:"attr=email"`
	from      string            `json:"from" valid:"lt=10, gt=1"` // unexported, will be ignored by qvalid
}

type BadTag struct {
	Err1 string `valid:"lt=10, lte=1"`            // this will cause [qvalid] error msg
	Err2 string `valid:"gt=10, gte=1"`            // this will cause [qvalid] error msg
	Err3 string `valid:"lt=10, gt=1, in=[aa,bb]"` // this will cause [qvalid] error msg
	Err4 string `valid:"lt=1, gte=1"`             // this will cause [qvalid] error msg
}

type FakeFood struct {
	Leaf     Leaf
	MainLeaf *Leaf
}

type Food struct {
	Leafs []Leaf `valid:"gte=1"`
}

type Leaf struct {
	Name string `valid:"in=[rose,tulip]" json:"name"`
}

validate struct with simple field

like Dog

func validateSimpleField() {
	dog := &Dog{}
	isPass, validErrors := qvalid.ValidateStruct(dog)
	fmt.Println("validateSimpleField")
	checkAndDumpValidErrors(isPass, validErrors)

	newFlower := &Dog{
		Name:      "rose",
		Color:     "gray",
		Weight:    30.0,
		Clothes:   3,
		NickNames: []string{"wangcai", "dawang"},
		Relations: map[string]string{
			"owner": "cy",
			"birth": "2018",
		},
		Email: "[email protected]",
	}
	isPass, validErrors = qvalid.ValidateStruct(newFlower)
	checkAndDumpValidErrors(isPass, validErrors)
}

output:

validateSimpleField
    illegal input and result:
        isPass:false
        validErrors:
            err:0 --> &{Field:.name Msg:value: not in:[rose tulip]}
            err:1 --> &{Field:.color Msg:expect length >= 3 but get length: 0}
            err:2 --> &{Field:.weight Msg:expect value >= 10 but get value:0}
            err:3 --> &{Field:.clothes Msg:value:0 not in:[1 3 5]}
            err:4 --> &{Field:.NickNames Msg:expect length > 1 but get length: 0}
            err:5 --> &{Field:.Relations Msg:expect length > 1 but get length: 0}
            err:6 --> &{Field:.Email Msg:value: not match attribute:email}

    legal input and result:
        isPass:true

validate embedded struct

like FakeFood

func validateEmbedStruct() {
	food := &FakeFood{
		MainLeaf: &Leaf{},
	}
	isPass, validErrors := qvalid.ValidateStruct(food)
	fmt.Println("validateEmbedStruct")
	checkAndDumpValidErrors(isPass, validErrors)

	newFakeFood := FakeFood{
		Leaf: Leaf{
			Name: "rose",
		},
		MainLeaf: &Leaf{
			Name: "rose",
		},
	}
	isPass, validErrors = qvalid.ValidateStruct(newFakeFood)
	checkAndDumpValidErrors(isPass, validErrors)
}

output

validateEmbedStruct
    illegal input and result:
        isPass:false
        validErrors:
            err:0 --> &{Field:.Leaf.name Msg:value: not in:[rose tulip]}
            err:1 --> &{Field:.MainLeaf.name Msg:value: not in:[rose tulip]}

    legal input and result:
        isPass:true
        

validate slice embedded struct

like Food

func validateSliceEmbedStruct() {
	food := &Food{
		Leafs: []Leaf{ // if Leafs is empty, qvalid do not check empty slice field, so set 1 element to test
			Leaf{},
		},
	}
	isPass, validErrors := qvalid.ValidateStruct(food)
	fmt.Println("validateSliceEmbedStruct")
	checkAndDumpValidErrors(isPass, validErrors)

	newFood := Food{
		Leafs: []Leaf{
			Leaf{
				Name: "rose",
			},
		},
	}
	isPass, validErrors = qvalid.ValidateStruct(newFood)
	checkAndDumpValidErrors(isPass, validErrors)
}

output

validateSliceEmbedStruct
    illegal input and result:
        isPass:false
        validErrors:
            err:0 --> &{Field:.Leafs[0].name Msg:value: not in:[rose tulip]}

    legal input and result:
        isPass:true
        

sample of bad tag

like Person

func badTag() {
	bad := &BadTag{}

	isPass, validErrors := qvalid.ValidateStruct(bad)
	fmt.Println("badTag")
	checkAndDumpValidErrors(isPass, validErrors)
}

output

badTag
    illegal input and result:
        isPass:false
        validErrors:
            err:0 --> &{Field:[qvalid] GetConstraintFromTag Msg:lt and lte can't both set}
            err:1 --> &{Field:[qvalid] GetConstraintFromTag Msg:gt and gt can't both set}
            err:2 --> &{Field:[qvalid] GetConstraintFromTag Msg:bound limit and 'in' can't both set}
            err:3 --> &{Field:[qvalid] GetConstraintFromTag Msg:upper and lower bound limit illegal}
            

for more details, see example dir.

TODO:

1. check pointer loop
2. customized field validator