dongshaidu2456
dongshaidu2456
2018-01-22 19:22

如何在Golang中访问嵌套的Json键值

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Team, new to Programming. I have data available after unmarshaling the Json as shown below, which has nested Key values. flat key values I am able to access, how do I access nested key values. Here is the byte slice data shown below after unmarshaling —>

tables:[map[name:basic__snatpool_members] map[name:net__snatpool_members] map[name:optimizations__hosts] map[columnNames:[name] name:pool__hosts rows:[map[row:[ry.hj.com]]]] traffic_group:/Common/traffic-group-1

Flat key values I am able to access by using the following code

p.TrafficGroup = m[“traffic_group”].(string)

here is the complete function

func dataToIapp(name string, d *schema.ResourceData) bigip.Iapp {
        var p bigip.Iapp

        var obj interface{}

        jsonblob := []byte(d.Get("jsonfile").(string))
        err := json.Unmarshal(jsonblob, &obj)
        if err != nil {
                fmt.Println("error", err)
        }
        m := obj.(map[string]interface{}) // Important: to access property
        p.Name = m[“name”].(string)
        p.Partition = m[“partition”].(string)

        p.InheritedDevicegroup = m[“inherited_devicegroup”].(string)

}
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3条回答

  • doubipiao1611 doubipiao1611 3年前

    Note: This may not work with your JSON structure. I inferred what it would be based on your question but without the actual structure, I cannot guarantee this to work without modification.

    If you want to access them in a map, you need to assert that the interface pulled from the first map is actually a map. So you would need to do this:

    tmp := m["tables"]
    tables, ok := tmp.(map[string]string)
    if !ok {
        //error handling here
    }
    
    r.Name = tables["name"].(string)
    

    But instead of accessing the unmarshaled JSON as a map[string]interface{}, why don't you create structs that match your JSON output?

    type JSONRoot struct {
        Name string `json:"name"`
        Partition string `json:"partition"`
        InheritedDevicegroup string `json:"inherited_devicegroup"`
        Tables map[string]string `json:"tables"` //Ideally, this would be a map of structs
    }
    

    Then in your code:

    func dataToIapp(name string, d *schema.ResourceData) bigip.Iapp {
        var p bigip.Iapp
    
        var obj &JSONRoot{}
    
        jsonblob := []byte(d.Get("jsonfile").(string))
        err := json.Unmarshal(jsonblob, &obj)
        if err != nil {
                fmt.Println("error", err)
        }
    
        p.Name = obj.Name
        p.Partition = obj.Partition
    
        p.InheritedDevicegroup = obj.InheritedDevicegroup
    
        p.Name = obj.Tables["name"]
    }
    
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  • doulin4844 doulin4844 3年前

    JSON objects are unmarshaled into map[string]interface{}, JSON arrays into []interface{}, same applies for nested objects/arrays.

    So for example if a key/index maps to a nested object you need to type assert the value to map[string]interface{} and if the key/index maps to an array of objects you first need to assert the value to []interface{} and then each element to map[string]interface{}.

    e.g. (for brevity this code is not guarding against panic)

    tables := obj.(map[string]interface{})["tables"]
    table1 := tables.([]interface{})[0]
    name := table1.(map[string]interface{})["name"]
    namestr := name.(string)
    

    However, if it's the case that the json you are parsing is not dynamic but instead has a specific structure you should define a struct type that mirrors that structure and unmarshal the json into that.

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  • drgd73844 drgd73844 3年前

    All you have to do is repeatedly accessing the map via type-switching or assertion:

    for _, table := range m["tables"] {
        switch val := table {
            case string:
                    fmt.Println("table is string")
            case int:
                    fmt.Println("table is integer")
    
            // This is your case, since JSON is unmarshaled to type []interface{} and map[string]interface{}
            case []interface{}:
                    fmt.Println("table is a slice of interface{}")
                    for _, tb := range value {
                            if m, ok := tb.(map[string]interface{}); ok {
                                    // Now it's accessible
                                    fmt.Println(m["name"])
    
                            }
                    }
            default:
                    fmt.Println("unknown type")
            }
    }
    

    You might want to handle errors better than this.

    To read more, check out my writing from a while ago https://medium.com/code-zen/dynamically-creating-instances-from-key-value-pair-map-and-json-in-go-feef83ab9db2.

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