如何在Golang中使用动态键解析YAML

Question

我正在尝试使用Go解析YAML文件。问题在于YAML文件中的密钥可能并不总是相同。这是为了进行API版本控制，以便用户可以定义他们支持的版本。例如V1，V2，V3等。它们不需要按顺序排列，并且可以省略它们不支持的版本，例如V0，V2，V5等。

package main

import (
  "fmt"
  "gopkg.in/yaml.v2"
)

var data = `
---
development:
  skip-header-validation: true
  V1:
    current: "1.0.0"
    mime_types:
      - application/vnd.company.jk.identity+json;
      - application/vnd.company.jk.user+json;
      - application/vnd.company.jk.role+json;
      - application/vnd.company.jk.scope+json;
      - application/vnd.company.jk.test+json;
    skip-mime-type-validation: true
    skip-version-validation: true
  V2:
    current: "2.0.0"
    mime_types:
      - application/vnd.company.jk.identity+json;
      - application/vnd.company.jk.user+json;
      - application/vnd.company.jk.role+json;
      - application/vnd.company.jk.scope+json;
      - application/vnd.company.jk.test+json;

`

type MajorVersion struct {
  Current                 string    `yaml:"current"`
  MimeTypes               []string  `yaml:"mime_types"`
  SkipVersionValidation   bool      `yaml:"skip-version-validation"`
  SkipMimeTypeValidation  bool      `yaml:"skip-mime-type-validation"`
}

type Environment struct {
  SkipHeaderValidation  bool        `yaml:"skip-header-validation"`
  Version               map[string]MajorVersion
}

func main() {
  e := Environment{}

  yaml.Unmarshal([]byte(data), &e)
  fmt.Println(e)
}

这是最高层，我还没有从结构内部弄清楚如何做到这一点。

Answer 1

首先，您尝试将根解析为Environment，但其实际类型为map[string]Environment。其次，Unmarshaler如果要保留该类型结构，则需要一个自定义项。像这样：

package main

import (
    "fmt"

    "gopkg.in/yaml.v2"
)

var data = `
---
development:
  skip-header-validation: true
  V1:
    current: "1.0.0"
    mime_types:
      - application/vnd.company.jk.identity+json;
      - application/vnd.company.jk.user+json;
      - application/vnd.company.jk.role+json;
      - application/vnd.company.jk.scope+json;
      - application/vnd.company.jk.test+json;
    skip-mime-type-validation: true
    skip-version-validation: true
  V2:
    current: "2.0.0"
    mime_types:
      - application/vnd.company.jk.identity+json;
      - application/vnd.company.jk.user+json;
      - application/vnd.company.jk.role+json;
      - application/vnd.company.jk.scope+json;
      - application/vnd.company.jk.test+json;

`

type MajorVersion struct {
    Current                string   `yaml:"current"`
    MimeTypes              []string `yaml:"mime_types"`
    SkipVersionValidation  bool     `yaml:"skip-version-validation"`
    SkipMimeTypeValidation bool     `yaml:"skip-mime-type-validation"`
}

type Environment struct {
    SkipHeaderValidation bool
    Versions             map[string]MajorVersion
}

func (e *Environment) UnmarshalYAML(unmarshal func(interface{}) error) error {
    var params struct {
        SkipHeaderValidation bool `yaml:"skip-header-validation"`
    }
    if err := unmarshal(&params); err != nil {
        return err
    }
    var versions map[string]MajorVersion
    if err := unmarshal(&versions); err != nil {
        // Here we expect an error because a boolean cannot be converted to a
        // a MajorVersion
        if _, ok := err.(*yaml.TypeError); !ok {
            return err
        }
    }
    e.SkipHeaderValidation = params.SkipHeaderValidation
    e.Versions = versions
    return nil
}

func main() {
    var e map[string]Environment
    if err := yaml.Unmarshal([]byte(data), &e); err != nil {
        fmt.Println(err.Error())
    }
    fmt.Printf("%#v\n", e)
}

输出（使用化妆后）：

map[string]main.Environment{
    "development": {
        SkipHeaderValidation: true,
        Versions:             {
            "V2": {
                Current:                "2.0.0",
                MimeTypes:              {"application/vnd.company.jk.identity+json;", "application/vnd.company.jk.user+json;", "application/vnd.company.jk.role+json;", "application/vnd.company.jk.scope+json;", "application/vnd.company.jk.test+json;"},
                SkipVersionValidation:  false,
                SkipMimeTypeValidation: false,
            },
            "V1": {
                Current:                "1.0.0",
                MimeTypes:              {"application/vnd.company.jk.identity+json;", "application/vnd.company.jk.user+json;", "application/vnd.company.jk.role+json;", "application/vnd.company.jk.scope+json;", "application/vnd.company.jk.test+json;"},
                SkipVersionValidation:  true,
                SkipMimeTypeValidation: true,
            },
        },
    },
}