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122 lines
3.1 KiB
Markdown
122 lines
3.1 KiB
Markdown
# YAML marshaling and unmarshaling support for Go
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[](https://travis-ci.org/ghodss/yaml)
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## Introduction
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A wrapper around [go-yaml](https://github.com/go-yaml/yaml) designed to enable a better way of handling YAML when marshaling to and from structs.
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In short, this library first converts YAML to JSON using go-yaml and then uses `json.Marshal` and `json.Unmarshal` to convert to or from the struct. This means that it effectively reuses the JSON struct tags as well as the custom JSON methods `MarshalJSON` and `UnmarshalJSON` unlike go-yaml. For a detailed overview of the rationale behind this method, [see this blog post](http://ghodss.com/2014/the-right-way-to-handle-yaml-in-golang/).
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## Compatibility
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This package uses [go-yaml](https://github.com/go-yaml/yaml) and therefore supports [everything go-yaml supports](https://github.com/go-yaml/yaml#compatibility).
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## Caveats
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**Caveat #1:** When using `yaml.Marshal` and `yaml.Unmarshal`, binary data should NOT be preceded with the `!!binary` YAML tag. If you do, go-yaml will convert the binary data from base64 to native binary data, which is not compatible with JSON. You can still use binary in your YAML files though - just store them without the `!!binary` tag and decode the base64 in your code (e.g. in the custom JSON methods `MarshalJSON` and `UnmarshalJSON`). This also has the benefit that your YAML and your JSON binary data will be decoded exactly the same way. As an example:
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```
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BAD:
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exampleKey: !!binary gIGC
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GOOD:
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exampleKey: gIGC
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... and decode the base64 data in your code.
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```
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**Caveat #2:** When using `YAMLToJSON` directly, maps with keys that are maps will result in an error since this is not supported by JSON. This error will occur in `Unmarshal` as well since you can't unmarshal map keys anyways since struct fields can't be keys.
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## Installation and usage
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To install, run:
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```
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$ go get github.com/ghodss/yaml
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```
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And import using:
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```
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import "github.com/ghodss/yaml"
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```
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Usage is very similar to the JSON library:
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```go
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package main
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import (
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"fmt"
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"github.com/ghodss/yaml"
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)
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type Person struct {
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Name string `json:"name"` // Affects YAML field names too.
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Age int `json:"age"`
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}
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func main() {
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// Marshal a Person struct to YAML.
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p := Person{"John", 30}
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y, err := yaml.Marshal(p)
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if err != nil {
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fmt.Printf("err: %v\n", err)
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return
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}
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fmt.Println(string(y))
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/* Output:
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age: 30
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name: John
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*/
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// Unmarshal the YAML back into a Person struct.
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var p2 Person
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err = yaml.Unmarshal(y, &p2)
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if err != nil {
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fmt.Printf("err: %v\n", err)
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return
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}
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fmt.Println(p2)
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/* Output:
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{John 30}
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*/
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}
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```
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`yaml.YAMLToJSON` and `yaml.JSONToYAML` methods are also available:
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```go
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package main
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import (
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"fmt"
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"github.com/ghodss/yaml"
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)
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func main() {
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j := []byte(`{"name": "John", "age": 30}`)
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y, err := yaml.JSONToYAML(j)
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if err != nil {
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fmt.Printf("err: %v\n", err)
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return
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}
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fmt.Println(string(y))
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/* Output:
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name: John
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age: 30
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*/
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j2, err := yaml.YAMLToJSON(y)
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if err != nil {
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fmt.Printf("err: %v\n", err)
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return
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}
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fmt.Println(string(j2))
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/* Output:
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{"age":30,"name":"John"}
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*/
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}
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```
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