Unstructed Data

结构化数据 Unstructed Data

数据可以分为结构化数据和非结构化数据。

1. 结构化数据：预先知道结构的数据，例如Json

   {
   "id": 1,
   "name": "kylinxiang"
   }

2. 处理结构化数据，需要一个对应的结构体 ```go package main

import ( “encoding/json” “fmt” )

// Student stores student info type Student struct { ID int Name string }

func main() { s := {"id": 1, "name": "kylinxiang"} var student Student err := json.Unmarshal([]byte(s), &student) if err != nil { fmt.Println(err.Error()) } fmt.Printf(“%v”, student) }

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## 非结构化数据 Unstructed Data
非结构化数据：无法预知数据类型或属性名称，无法通过构建预定的struct数据结构来序列化和反序列化数据。例如：
```json
{
  "id": 1,
  "name": "kylinxiang",
  "description": ...  //无法预知其数据类型，所以不能处理
}

因为Go语言是强类型语言，它需要预先知道数据类型，所以在处理JSON数据时不如动态语言便捷。
当无法预知数据结构类型和属性名称时，可以使用如下的结构来解决问题：

var result map[string]interface{}

每个字符串对应一个JSON属性，其映射interface{}类型对应值，可以是任意类型。
使用interface{}字段时，通过Go语言类型断言的方式进行类型转换。

package main
import "fmt"
func main() {
    result := make(map[string]interface{})
    result["description"] = "kylinxiang"
    if description, ok := result["description"].(string); ok {
        fmt.Println(description)
    }
}

Kubernetes非结构化数据处理

代码路径：vendor/k8s.io/apimachinery/pkg/runtime/interfaces.go

// Unstructured objects store values as map[string]interface{}, with only values that can be serialized
// to JSON allowed.
type Unstructured interface {
    Object
    // NewEmptyInstance returns a new instance of the concrete type containing only kind/apiVersion and no other data.
    // This should be called instead of reflect.New() for unstructured types because the go type alone does not preserve kind/apiVersion info.
    NewEmptyInstance() Unstructured
    // UnstructuredContent returns a non-nil map with this object's contents. Values may be
    // []interface{}, map[string]interface{}, or any primitive type. Contents are typically serialized to
    // and from JSON. SetUnstructuredContent should be used to mutate the contents.
    UnstructuredContent() map[string]interface{}
    // SetUnstructuredContent updates the object content to match the provided map.
    SetUnstructuredContent(map[string]interface{})
    // IsList returns true if this type is a list or matches the list convention - has an array called "items".
    IsList() bool
    // EachListItem should pass a single item out of the list as an Object to the provided function. Any
    // error should terminate the iteration. If IsList() returns false, this method should return an error
    // instead of calling the provided function.
    EachListItem(func(Object) error) error
}
// Object interface must be supported by all API types registered with Scheme. Since objects in a scheme are
// expected to be serialized to the wire, the interface an Object must provide to the Scheme allows
// serializers to set the kind, version, and group the object is represented as. An Object may choose
// to return a no-op ObjectKindAccessor in cases where it is not expected to be serialized.
type Object interface {
    GetObjectKind() schema.ObjectKind
    DeepCopyObject() Object
}

代码路径：vendor/k8s.io/apimachinery/pkg/apis/meta/v1/unstructed/unstructed.go

type Unstructured struct {
    // Object is a JSON compatible map with string, float, int, bool, []interface{}, or
    // map[string]interface{}
    // children.
    Object map[string]interface{}
}

上述代码中，Kubernetes非结构化数据通过map[string]interface{}表达，并提供接口。在client-go编程式交互的DynamicClient内部，实现了Unstructed类型，用于处理非结构化数据。