I have the following JSON array received as a web service output using CURL.
{
"total_rows": 4,
"offset": 0,
"rows": [
{
"id": "_design/people",
"key": "_design/people",
"value": {
"rev": "3-d707964c8a3fa0c0c71e51c600bbafb8"
}
},
{
"id": "aamir",
"key": "aamir",
"value": {
"rev": "3-4b9095435470366fb77df1a3d466bcff"
}
},
{
"id": "iyaan",
"key": "iyaan",
"value": {
"rev": "1-4fea2c459d85480bf4841c7e581180c0"
}
},
{
"id": "tahir",
"key": "tahir",
"value": {
"rev": "2-593c9237a96836a98f53c0374902964a"
}
}
]
}
I want to extract the "total_rows" object separately from it and "rows" object separately.
You just need the package encoding/json.
Defined Row struct:
type Row struct {
Id string `json:"id"`
Key string `json:"key"`
Value struct {
Rev string `json:"rev"`
} `json:"value"`
}
Defined Data Sturct:
type Data struct {
TotalRows int `json:"total_rows"`
Offset int `json:"offest"`
Rows []Row `json:"rows"`
}
And then use json.Unmarshal:
b := []byte("json string")
data := Data{}
if err := json.Unmarshal(b, &data); err != nil {
panic(err)
}
fmt.Println(data.TotalRows, data.Offset)
for _, row := range data.Rows {
fmt.Println(row.Id, row.Key)
}
As the other poster suggested, "encoding/json" will set you up with what you need. I will also recommend trying some of the third party libraries as they can maybe better fit your implementation. Initially I would suggest looking at:
https://github.com/buger/jsonparser
https://github.com/mailru/easyjson
These are just some quick suggestions and there are other libraries out there. Good luck!
Related
I'm trying to extract Protobuf custom options from a FileDescriptorSet generated by the protoc compiler. I'm unable to do so using protoreflect. So, I tried to do so using the protojson library.
PS : Importing the Go-generated code is not an option for my use case.
Here's the Protobuf Message I'm testing with :
syntax = "proto3";
option go_package = "./protoze";
import "google/protobuf/descriptor.proto";
extend google.protobuf.FieldOptions {
string Meta = 50000;
}
extend google.protobuf.FileOptions {
string Food = 50001;
}
option (Food) = "cheese";
message X {
int64 num = 1;
}
message P {
string Fname = 1 [json_name = "FNAME"];
string Lname = 2 [json_name = "0123", (Meta) = "Yo"];
string Designation = 3;
repeated string Email = 4;
string UserID = 5;
string EmpID = 6;
repeated X z = 7;
}
// protoc --go_out=. filename.proto
Here's how far I got :
package main
import (
"fmt"
"io/ioutil"
"os/exec"
"google.golang.org/protobuf/encoding/protojson"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/types/descriptorpb"
)
func main() {
exec.Command("protoc", "-oBinaryFile", "1.proto").Run()
Fset := descriptorpb.FileDescriptorSet{}
byts, _ := ioutil.ReadFile("File")
proto.Unmarshal(byts, &Fset)
byts, _ = protojson.Marshal(Fset.File[0])
fmt.Println(string(byts))
}
And here's the output JSON
{
"name": "1.proto",
"dependency": [
"google/protobuf/descriptor.proto"
],
"messageType": [
{
"name": "X",
"field": [
{
"name": "num",
"number": 1,
"label": "LABEL_OPTIONAL",
"type": "TYPE_INT64",
"jsonName": "num"
}
]
},
{
"name": "P",
"field": [
{
"name": "Fname",
"number": 1,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"jsonName": "FNAME"
},
{
"name": "Lname",
"number": 2,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"jsonName": "0123",
"options": {}
},
{
"name": "Designation",
"number": 3,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"jsonName": "Designation"
},
{
"name": "Email",
"number": 4,
"label": "LABEL_REPEATED",
"type": "TYPE_STRING",
"jsonName": "Email"
},
{
"name": "UserID",
"number": 5,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"jsonName": "UserID"
},
{
"name": "EmpID",
"number": 6,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"jsonName": "EmpID"
},
{
"name": "z",
"number": 7,
"label": "LABEL_REPEATED",
"type": "TYPE_MESSAGE",
"typeName": ".X",
"jsonName": "z"
}
]
}
],
"extension": [
{
"name": "Meta",
"number": 50000,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"extendee": ".google.protobuf.FieldOptions",
"jsonName": "Meta"
},
{
"name": "Food",
"number": 50001,
"label": "LABEL_OPTIONAL",
"type": "TYPE_STRING",
"extendee": ".google.protobuf.FileOptions",
"jsonName": "Food"
}
],
"options": {
"goPackage": "./protoze"
},
"syntax": "proto3"
}
So, data about my custom options showed up in the extensions. But what I really wanted was the value of those Custom Options in the "options" as well. (Which in my case was (Food) = "Cheese" and I want Cheese)
Can someone tell me how I can extract my custom options from the FileDescriptorSet using Protoreflect or by using Protojson.
I tried a lot to try and extract it using Protoreflect but failed !
Although not specifically an answer to how to get the custom options in a generated JSON, I believe I have an answer to what sounds like your underlying question: how to access the custom options without loading the generated Go code. This is thanks to dsnet's answer to my question on the golang issues board. Needless to say all the credit for this tricky solution goes to him. The punchline is to Marshal and then Unmarshal the options using a runtime-populated protoregistry.Types that actually knows about the custom options.
I made a complete demonstration of this approach working in this repo, and the key section (all the guts of which come from dsnet's example) is here:
func main() {
protogen.Options{
}.Run(func(gen *protogen.Plugin) error {
gen.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)
// The type information for all extensions is in the source files,
// so we need to extract them into a dynamically created protoregistry.Types.
extTypes := new(protoregistry.Types)
for _, file := range gen.Files {
if err := registerAllExtensions(extTypes, file.Desc); err != nil {
panic(err)
}
}
// run through the files again, extracting and printing the Message options
for _, sourceFile := range gen.Files {
if !sourceFile.Generate {
continue
}
// setup output file
outputfile := gen.NewGeneratedFile("./out.txt", sourceFile.GoImportPath)
for _, message := range sourceFile.Messages {
outputfile.P(fmt.Sprintf("\nMessage %s:", message.Desc.Name()))
// The MessageOptions as provided by protoc does not know about
// dynamically created extensions, so they are left as unknown fields.
// We round-trip marshal and unmarshal the options with
// a dynamically created resolver that does know about extensions at runtime.
options := message.Desc.Options().(*descriptorpb.MessageOptions)
b, err := proto.Marshal(options)
if err != nil {
panic(err)
}
options.Reset()
err = proto.UnmarshalOptions{Resolver: extTypes}.Unmarshal(b, options)
if err != nil {
panic(err)
}
// Use protobuf reflection to iterate over all the extension fields,
// looking for the ones that we are interested in.
options.ProtoReflect().Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
if !fd.IsExtension() {
return true
}
outputfile.P(fmt.Sprintf("Value of option %s is %s",fd.Name(), v.String()))
// Make use of fd and v based on their reflective properties.
return true
})
}
}
return nil
})
}
// Recursively register all extensions into the provided protoregistry.Types,
// starting with the protoreflect.FileDescriptor and recursing into its MessageDescriptors,
// their nested MessageDescriptors, and so on.
//
// This leverages the fact that both protoreflect.FileDescriptor and protoreflect.MessageDescriptor
// have identical Messages() and Extensions() functions in order to recurse through a single function
func registerAllExtensions(extTypes *protoregistry.Types, descs interface {
Messages() protoreflect.MessageDescriptors
Extensions() protoreflect.ExtensionDescriptors
}) error {
mds := descs.Messages()
for i := 0; i < mds.Len(); i++ {
registerAllExtensions(extTypes, mds.Get(i))
}
xds := descs.Extensions()
for i := 0; i < xds.Len(); i++ {
if err := extTypes.RegisterExtension(dynamicpb.NewExtensionType(xds.Get(i))); err != nil {
return err
}
}
return nil
}
I need to create dynamic json i.e whose key value varies, below mentioned is the json
[{"email":"xxx#gmail.com","location":{"set":"Redmond"},"fname":{"set":"xxxxx"},"clicked_time":{"set":"zz"},"domain":{"add":"ttt"}},{"email":"zzz#gmail.com","location":{"set":"Greece"},"fname":{"set":"zzzzz"},"clicked_time":{"set":"zzz"},"domain":{"add":"zxxxx"}}]
I tried using below code:
rows := []map[string]string{}
if i > 0 {
row := make(map[string]string)
for j:=0;j<len(record);j++ {
key := header[j]
value := record[j]
row[key] = value
}
rows = append(rows, row)
}
How may I add set to location and add to domain to create a nested structure as map can have only one type string or nested structure?
Perhaps I have missed the point a little here, but I am not seeing why this is so dynamic in a way that can't be handled by a struct and the json unmarshal method.
Please see the following for an example
https://play.golang.org/p/8nrO36HQGhy
package main
import (
"encoding/json"
"fmt"
)
type (
Details struct {
Email string `json:"email"`
Location Entry `json:"location"`
FName Entry `json:"fname"`
ClickedTime Entry `json:"clicked_time"`
Domain Entry `json:"domain"`
}
Entry struct {
Set string `json:"set"`
Add string `json:"add"`
}
)
func main() {
d := []byte(`[{
"email": "xxx#gmail.com",
"location": {
"set": "Redmond"
},
"fname": {
"set": "xxxxx"
},
"clicked_time": {
"set": "zz"
},
"domain": {
"add": "ttt"
}
}, {
"email": "zzz#gmail.com",
"location": {
"set": "Greece"
},
"fname": {
"set": "zzzzz"
},
"clicked_time": {
"set": "zzz"
},
"domain": {
"add": "zxxxx"
}
}]`)
x := []Details{}
_ = json.Unmarshal(d, &x)
fmt.Printf("%+v\n", x)
}
I have a (non)working example here: https://play.golang.org/p/qaYhKvJ65J3
I'm not sure why the following data:
alertData := `{
"Id": 0,
"Version": 0,
"OrgId": 1,
"DashboardId": 61,
"PanelId": 84,
"Name": "{qa-dev}{stats-pipeline} Topology Message Age (aggregator) alert",
"Message": "",
"Severity": "",
"State": "",
"Handler": 1,
"Silenced": false,
"ExecutionError": "",
"Frequency": 10,
"EvalData": null,
"NewStateDate": "0001-01-01T00:00:00Z",
"PrevStateDate": "0001-01-01T00:00:00Z",
"StateChanges": 0,
"Created": "0001-01-01T00:00:00Z",
"Updated": "0001-01-01T00:00:00Z",
"Settings": {
"conditions": [
{
"evaluator": {
"params": [
10000
],
"type": "gt"
},
"operator": {
"type": "and"
},
"query": {
"datasourceId": 2,
"model": {
"hide": true,
"refCount": 0,
"refId": "C",
"textEditor": false
},
"params": [
"C",
"5m",
"now"
]
},
"reducer": {
"params": [],
"type": "avg"
},
"type": "query"
}
],
"executionErrorState": "keep_state",
"frequency": "10s",
"handler": 1,
"name": "{qa-dev}{stats-pipeline} Topology Message Age (aggregator) alert",
"noDataState": "keep_state",
"notifications": []
}
}`
Can't be unmarshalled into the following object model:
type Condition struct {
Evaluator struct {
Params []int `json:"params"`
Type string `json:"type"`
} `json:"evaluator"`
Operator struct {
Type string `json:"type"`
} `json:"operator"`
Query struct {
Params []string `json:"params"`
} `json:"query"`
Reducer struct {
Params []interface{} `json:"params"`
Type string `json:"type"`
} `json:"reducer"`
Type string `json:"type"`
}
When I do the following:
condition := Condition{}
err := json.Unmarshal([]byte(alertData), &condition)
if err != nil {
panic(err)
}
fmt.Printf("\n\n json object:::: %+v", condition)
I just get: json object:::: {Evaluator:{Params:[] Type:} Operator:{Type:} Query:{Params:[]} Reducer:{Params:[] Type:} Type:}
Ideally I'd be able to parse it into something like type Conditions []struct{ } but I'm not sure if you can define models as lists?
It looks like you are trying to access the "conditions" property nested under the root "Settings" property. As such, you need to define that root-level type and enough fields to tell the unmarshaler how to find your target property. As such, you would just need to create a new "AlertData" type with the necessary "Settings/conditions" fields.
For example (Go Playground):
type AlertData struct {
Settings struct {
Conditions []Condition `json:"conditions"`
}
}
func main() {
alert := AlertData{}
err := json.Unmarshal([]byte(alertData), &alert)
if err != nil {
panic(err)
}
fmt.Printf("OK: conditions=%#v\n", alert.Settings.Conditions)
// OK: conditions=[]main.Condition{main.Condition{Evaluator:struct { Params []int "json:\"params\""; Type string "json:\"type\"" }{Params:[]int{10000}, Type:"gt"}, Operator:struct { Type string "json:\"type\"" }{Type:"and"}, Query:struct { Params []string "json:\"params\"" }{Params:[]string{"C", "5m", "now"}}, Reducer:struct { Params []interface {} "json:\"params\""; Type string "json:\"type\"" }{Params:[]interface {}{}, Type:"avg"}, Type:"query"}}
}
Note that the printed listing includes so much type information because the "Condition" type uses anonymous structs as field types. If you were to extract them into named structs it will be easier to work with the data, e.g.:
type Condition struct {
Evaluator Evaluator `json:"evaluator"`
Operator Operator `json:"operator"`
// ...
}
type Evaluator struct {
Params []int `json:"params"`
Type string `json:"type"`
}
type Operator struct {
Type string `json:"type"`
}
//...
// OK: conditions=[]main.Condition{
// main.Condition{
// Evaluator:main.Evaluator{Params:[]int{10000}, Type:"gt"},
// Operator:main.Operator{Type:"and"},
// Query:main.Query{Params:[]string{"C", "5m", "now"}},
// Reducer:main.Reducer{Params:[]interface {}{}, Type:"avg"},
// Type:"query",
// },
// }
Go Playground example here...
Maerics explanation is correct, here is an alternative approach which wraps access around struct methods, the data structure is also fully defined. If you're new to Go it's good to get handle on creating the data structures yourself, but here is a handy utility for helping create structs from valid JSON
https://mholt.github.io/json-to-go/
package main
import (
"encoding/json"
"fmt"
"log"
"time"
)
type Data struct {
ID int `json:"Id"`
Version int `json:"Version"`
OrgID int `json:"OrgId"`
DashboardID int `json:"DashboardId"`
PanelID int `json:"PanelId"`
Name string `json:"Name"`
Message string `json:"Message"`
Severity string `json:"Severity"`
State string `json:"State"`
Handler int `json:"Handler"`
Silenced bool `json:"Silenced"`
ExecutionError string `json:"ExecutionError"`
Frequency int `json:"Frequency"`
EvalData interface{} `json:"EvalData"`
NewStateDate time.Time `json:"NewStateDate"`
PrevStateDate time.Time `json:"PrevStateDate"`
StateChanges int `json:"StateChanges"`
Created time.Time `json:"Created"`
Updated time.Time `json:"Updated"`
Settings struct {
Conditions []Condition `json:"conditions"`
ExecutionErrorState string `json:"executionErrorState"`
Frequency string `json:"frequency"`
Handler int `json:"handler"`
Name string `json:"name"`
NoDataState string `json:"noDataState"`
Notifications []interface{} `json:"notifications"`
} `json:"Settings"`
}
type Condition struct {
Evaluator struct {
Params []int `json:"params"`
Type string `json:"type"`
} `json:"evaluator"`
Operator struct {
Type string `json:"type"`
} `json:"operator"`
Query struct {
DatasourceID int `json:"datasourceId"`
Model struct {
Hide bool `json:"hide"`
RefCount int `json:"refCount"`
RefID string `json:"refId"`
TextEditor bool `json:"textEditor"`
} `json:"model"`
Params []string `json:"params"`
} `json:"query"`
Reducer struct {
Params []interface{} `json:"params"`
Type string `json:"type"`
} `json:"reducer"`
Type string `json:"type"`
}
func (d Data) GetFirstCondition() (Condition, error) {
if len(d.Settings.Conditions) > 0 {
return d.Settings.Conditions[0], nil
}
return Condition{}, fmt.Errorf("no conditions found")
}
func (d Data) GetConditionByIndex(index uint) (Condition, error) {
if len(d.Settings.Conditions) == 0 {
return Condition{}, fmt.Errorf("no conditions found")
}
if int(index) > len(d.Settings.Conditions)-1 {
return Condition{}, fmt.Errorf("index out of bounds")
}
return d.Settings.Conditions[index], nil
}
var alertData = `{
"Id": 0,
"Version": 0,
"OrgId": 1,
"DashboardId": 61,
"PanelId": 84,
"Name": "{qa-dev}{stats-pipeline} Topology Message Age (aggregator) alert",
"Message": "",
"Severity": "",
"State": "",
"Handler": 1,
"Silenced": false,
"ExecutionError": "",
"Frequency": 10,
"EvalData": null,
"NewStateDate": "0001-01-01T00:00:00Z",
"PrevStateDate": "0001-01-01T00:00:00Z",
"StateChanges": 0,
"Created": "0001-01-01T00:00:00Z",
"Updated": "0001-01-01T00:00:00Z",
"Settings": {
"conditions": [
{
"evaluator": {
"params": [
10000
],
"type": "gt"
},
"operator": {
"type": "and"
},
"query": {
"datasourceId": 2,
"model": {
"hide": true,
"refCount": 0,
"refId": "C",
"textEditor": false
},
"params": [
"C",
"5m",
"now"
]
},
"reducer": {
"params": [],
"type": "avg"
},
"type": "query"
}
],
"executionErrorState": "keep_state",
"frequency": "10s",
"handler": 1,
"name": "{qa-dev}{stats-pipeline} Topology Message Age (aggregator) alert",
"noDataState": "keep_state",
"notifications": []
}
}`
func main() {
var res Data
err := json.Unmarshal([]byte(alertData), &res)
if err != nil {
log.Fatal(err)
}
fmt.Println(res.GetFirstCondition())
fmt.Println(res.GetConditionByIndex(0))
// should fail :-)
fmt.Println(res.GetConditionByIndex(1))
}
I am reading in a .json file. It's an array of objects in valid JSON format, example:
[
{
"Id": 13,
"Location": "Australia",
"Content": "Another string"
},
{
"Id": 145,
"Location": "England",
"Content": "SomeString"
},
{
"Id": 12,
"Location": "England",
"Content": "SomeString"
},
{
"Id": 12331,
"Location": "Sweden",
"Content": "SomeString"
},
{
"Id": 213123,
"Location": "England",
"Content": "SomeString"
}
]
I want to filter these objects out - say, removing anything where "Location"doesn't equal "England".
What I've tried so far is creating a custom UnmarshalJSON function. It does unmarshal it, but the objects it produces are empty - and as many as the input.
Sample code:
type languageStruct struct {
ID int `json:"Id"`
Location string `json:"Location"`
Content string `json:"Content"`
}
func filterJSON(file []byte) ([]byte, error) {
var x []*languageStruct
err := json.Unmarshal(file, &x)
check(err)
return json.MarshalIndent(x, "", " ")
}
func (s *languageStruct) UnmarshalJSON(p []byte) error {
var result struct {
ID int `json:"Id"`
Location string `json:"Location"`
Content string `json:"Content"`
}
err := json.Unmarshal(p, &result)
check(err)
// slice of locations we'd like to filter the objects on
locations := []string{"England"} // Can be more
if sliceContains(s.Location, locations) {
s.ID = result.ID
s.Location= result.Location
s.Content = result.Content
}
return nil
}
// helper func to check if a given string, f.e. a value of a key-value pair in a json object, is in a provided list
func sliceContains(a string, list []string) bool {
for _, b := range list {
if b == a {
fmt.Println("it's a match!")
return true
}
}
return false
}
While this runs - the output is wrong. It creates as many objects as comes in - however, the new ones are empty, f.e.:
// ...
[
{
"Id": 0,
"Location": "",
"Content": ""
},
{
"Id": 0,
"Location": "",
"Content": ""
}
]
//...
Whereas my desired output, from the first given input, would be:
[
{
"Id": 145,
"Location": "England",
"Content": "SomeString"
},
{
"Id": 12,
"Location": "England",
"Content": "SomeString"
},
{
"Id": 213123,
"Location": "England",
"Content": "SomeString"
}
]
When languageStruct.UnmarshalJSON() is called, there is already a languageStruct prepared that will be appended to the slice, no matter if you fill its content (fields) or not.
The easiest and my suggested solution is to just unmarshal normally, and post-process the slice: remove elements according to your requirements. This results in clean code, which you can easily adjust / alter in the future. Although it could be implemented as custom marshaling logic on a custom slice type []languageStruct, I would still not create custom marshaling logic for this but implement it as a separate filtering logic.
Here's a simple code unmarshaling, filtering and marshaling it again (note: no custom marshaling is defined / used for this):
var x []*languageStruct
err := json.Unmarshal(file, &x)
if err != nil {
panic(err)
}
var x2 []*languageStruct
for _, v := range x {
if v.Location == "England" {
x2 = append(x2, v)
}
}
data, err := json.MarshalIndent(x2, "", " ")
fmt.Println(string(data), err)
This will result in your desired output. Try it on the Go Playground.
The fastest and most complex solution would be to use event-driven parsing and building a state machine, but the complexity would increase by large. The idea would be to process the JSON by tokens, track where you're at currently in the object tree, and when an object is detected that must be excluded, don't process / add it to your slice. For details and ideas how this can be written, check out this anwser: Go - Decode JSON as it is still streaming in via net/http
I'm trying to decode some json in Go but some fields don't get decoded.
See the code running in browser here:
What am I doing wrong?
I need only the MX records so I didn't define the other fields. As I understand from the godoc you don't need to define the fields you don't use/need.
// You can edit this code!
// Click here and start typing.
package main
import "fmt"
import "encoding/json"
func main() {
body := `
{"response": {
"status": "SUCCESS",
"data": {
"mxRecords": [
{
"value": "us2.mx3.mailhostbox.com.",
"ttl": 1,
"priority": 100,
"hostName": "#"
},
{
"value": "us2.mx1.mailhostbox.com.",
"ttl": 1,
"priority": 100,
"hostName": "#"
},
{
"value": "us2.mx2.mailhostbox.com.",
"ttl": 1,
"priority": 100,
"hostName": "#"
}
],
"cnameRecords": [
{
"aliasHost": "pop.a.co.uk.",
"canonicalHost": "us2.pop.mailhostbox.com."
},
{
"aliasHost": "webmail.a.co.uk.",
"canonicalHost": "us2.webmail.mailhostbox.com."
},
{
"aliasHost": "smtp.a.co.uk.",
"canonicalHost": "us2.smtp.mailhostbox.com."
},
{
"aliasHost": "imap.a.co.uk.",
"canonicalHost": "us2.imap.mailhostbox.com."
}
],
"dkimTxtRecord": {
"domainname": "20a19._domainkey.a.co.uk",
"value": "\"v=DKIM1; g=*; k=rsa; p=DkfbhO8Oyy0E1WyUWwIDAQAB\"",
"ttl": 1
},
"spfTxtRecord": {
"domainname": "a.co.uk",
"value": "\"v=spf1 redirect=_spf.mailhostbox.com\"",
"ttl": 1
},
"loginUrl": "us2.cp.mailhostbox.com"
}
}}`
type MxRecords struct {
value string
ttl int
priority int
hostName string
}
type Data struct {
mxRecords []MxRecords
}
type Response struct {
Status string `json:"status"`
Data Data `json:"data"`
}
type apiR struct {
Response Response
}
var r apiR
err := json.Unmarshal([]byte(body), &r)
if err != nil {
fmt.Printf("err was %v", err)
}
fmt.Printf("decoded is %v", r)
}
As per the go documentaiton about json.Unmarshal, you can only decode toward exported fields, the main reason being that external packages (such as encoding/json) cannot acces unexported fields.
If your json doesn't follow the go convention for names, you can use the json tag in your fields to change the matching between json key and struct field.
Exemple:
package main
import (
"fmt"
"encoding/json"
)
type T struct {
Foo string `json:"foo"`
priv string `json:"priv"`
}
func main() {
text := []byte(`{"foo":"bar", "priv":"nothing"}`)
var t T
err := json.Unmarshal(text, &t)
if err != nil {
panic(err)
}
fmt.Println(t.Foo) // prints "bar"
fmt.Println(t.priv) // prints "", priv is not exported
}
You must Uppercase struct fields:
type MxRecords struct {
Value string `json:"value"`
Ttl int `json:"ttl"`
Priority int `json:"priority"`
HostName string `json:"hostName"`
}
type Data struct {
MxRecords []MxRecords `json:"mxRecords"`
}
http://play.golang.org/p/EEyiISdoaE
The encoding/json package can only decode into exported struct fields. Your Data.mxRecords member is not exported, so it is ignored when decoding. If you rename it to use a capital letter, the JSON package will notice it.
You will need to do the same thing for all the members of your MxRecords type.