Golang如何实现Web表单提交校验

type UserForm struct {
    Username string `form:"username" validate:"required,min=3,max=20"`
    Email    string `form:"email"    validate:"required,email"`
    Password string `form:"password" validate:"required,min=6"`
}

import (
    "github.com/go-playground/validator/v10"
)

var validate *validator.Validate

func init() {
    validate = validator.New()
}

func handleRegister(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        http.Error(w, "Method not allowed", 405)
        return
    }

    var form UserForm
    if err := r.ParseForm(); err != nil {
        http.Error(w, "Invalid form data", 400)
        return
    }

    // 绑定表单数据到结构体
    if err := r.ParseForm(); err == nil {
        _ = schema.NewDecoder().Decode(&form, r.PostForm)
    }

    // 执行校验
    if err := validate.Struct(form); err != nil {
        errors := make(map[string]string)
        for _, err := range err.(validator.ValidationErrors) {
            errors[err.Field()] = fmt.Sprintf("Field %s failed validation: %v", err.Field(), err.Tag())
        }
        w.WriteHeader(400)
        json.NewEncoder(w).Encode(errors)
        return
    }

    // 校验通过，继续处理业务逻辑
    w.Write([]byte("Registration successful"))
}

func (u *UserForm) Validate() map[string]string {
    errors := make(map[string]string)

    if u.Password != u.ConfirmPassword {
        errors["ConfirmPassword"] = "Passwords do not match"
    }

    // 检查用户名是否已存在（需查询数据库）
    if isUsernameTaken(u.Username) {
        errors["Username"] = "Username already exists"
    }

    return errors
}

{
  "Username": "Field Username failed validation: min",
  "Email": "Field Email failed validation: email"
}