This is a Go package that fully supports the Facebook Graph API with file upload, batch request and marketing API. It can be used in Google App Engine.
Feel free to create an issue or send me a pull request if you have any "how-to" question or bug or suggestion when using this package. I'll try my best to reply to it.
Install
If go mod is enabled, install this package with go get github.com/huandu/facebook/v2. If not, call go get -u github.com/huandu/facebook to get the latest master branch version.
Note that, since go1.14, incompatible versions are omitted unless specified explicitly. Therefore, it's highly recommended to upgrade the import path to github.com/huandu/facebook/v2 when possible to avoid any potential dependency error.
Usage
Quick start
Here is a sample that reads my Facebook first name by uid.
package main
import (
"fmt"
fb "github.com/huandu/facebook/v2"
)
funcmain() {
res, _:=fb.Get("/538744468", fb.Params{
"fields": "first_name",
"access_token": "a-valid-access-token",
})
fmt.Println("Here is my Facebook first name:", res["first_name"])
}
The type of res is fb.Result (a.k.a. map[string]interface{}).
This type has several useful methods to decode res to any Go type safely.
// Decode "first_name" to a Go string.varfirst_namestringres.DecodeField("first_name", &first_name)
fmt.Println("Here's an alternative way to get first_name:", first_name)
// It's also possible to decode the whole result into a predefined struct.typeUserstruct {
FirstNamestring
}
varuserUserres.Decode(&user)
fmt.Println("print first_name in struct:", user.FirstName)
If a type implements the json.Unmarshaler interface, Decode or DecodeField will use it to unmarshal JSON.
res:=Result{
"create_time": "2006-01-02T15:16:17Z",
}
// Type `*time.Time` implements `json.Unmarshaler`.// res.DecodeField will use the interface to unmarshal data.vartm time.Timeres.DecodeField("create_time", &tm)
Read a graph user object with a valid access token
res, err:=fb.Get("/me/feed", fb.Params{
"access_token": "a-valid-access-token",
})
iferr!=nil {
// err can be a Facebook API error.// if so, the Error struct contains error details.ife, ok:=err.(*Error); ok {
fmt.Printf("facebook error. [message:%v] [type:%v] [code:%v] [subcode:%v] [trace:%v]",
e.Message, e.Type, e.Code, e.ErrorSubcode, e.TraceID)
return
}
// err can be an unmarshal error when Facebook API returns a message which is not JSON.ife, ok:=err.(*UnmarshalError); ok {
fmt.Printf("facebook error. [message:%v] [err:%v] [payload:%v]",
e.Message, e.Err, string(e.Payload))
return
}
return
}
// read my last feed story.fmt.Println("My latest feed story is:", res.Get("data.0.story"))
Read a graph search for page and decode slice of maps
It's recommended to use App and Session in a production app. They provide more control over all API calls. They can also make code clearer and more concise.
// Create a global App var to hold app id and secret.varglobalApp=fb.New("your-app-id", "your-app-secret")
// Facebook asks for a valid redirect URI when parsing the signed request.// It's a newly enforced policy starting as of late 2013.globalApp.RedirectUri="http://your.site/canvas/url/"// Here comes a client with a Facebook signed request string in the query string.// This will return a new session from a signed request.session, _:=globalApp.SessionFromSignedRequest(signedRequest)
// If there is another way to get decoded access token,// this will return a session created directly from the token.session:=globalApp.Session(token)
// This validates the access token by ensuring that the current user ID is properly returned. err is nil if the token is valid.err:=session.Validate()
// Use the new session to send an API request with the access token.res, _:=session.Get("/me/feed", nil)
By default, all requests are sent to Facebook servers. If you wish to override the API base URL for unit-testing purposes - just set the respective Session field.
Facebook returns most timestamps in an ISO9601 format which can't be natively parsed by Go's encoding/json.
Setting RFC3339Timestampstrue on the Session or at the global level will cause proper RFC3339 timestamps to be requested from Facebook.
RFC3339 is what encoding/json natively expects.
Setting either of these to true will cause date_format=Y-m-d\TH:i:sP to be sent as a parameter on every request. The format string is a PHP date() representation of RFC3339.
More info is available in this issue.
Use paging field in response
Some Graph API responses use a special JSON structure to provide paging information. Use Result.Paging() to walk through all data in such results.
res, _:=session.Get("/me/home", nil)
// create a paging structure.paging, _:=res.Paging(session)
varallResults []Result// append first page of results to slice of ResultallResults=append(allResults, paging.Data()...)
for {
// get next page.noMore, err:=paging.Next()
iferr!=nil {
panic(err)
}
ifnoMore {
// No more results availablebreak
}
// append current page of results to slice of ResultallResults=append(allResults, paging.Data()...)
}
Read Graph API response and decode result in a struct
The Facebook Graph API always uses snake case keys in API response.
This package can automatically convert from snake case to Go's camel-case-style style struct field names.
For instance, to decode the following JSON response...
{
"foo_bar": "player"
}
One can use the following struct.
typeDatastruct {
FooBarstring// "FooBar" maps to "foo_bar" in JSON automatically in this case.
}
The decoding of each struct field can be customized by the format string stored under the facebook key or the "json" key in the struct field's tag. The facebook key is recommended as it's specifically designed for this package.
Following is a sample that shows all possible field tags.
// define a Facebook feed object.typeFacebookFeedstruct {
Idstring`facebook:",required"`// this field must exist in response.// mind the "," before "required".StorystringFeedFrom*FacebookFeedFrom`facebook:"from"`// use customized field name "from".CreatedTimestring`facebook:"created_time,required"`// both customized field name and "required" flag.Omittedstring`facebook:"-"`// this field is omitted when decoding.
}
typeFacebookFeedFromstruct {
Namestring`json:"name"`// the "json" key also works as expected.Idstring`facebook:"id" json:"shadowed"`// if both "facebook" and "json" key are set, the "facebook" key is used.
}
// create a feed object direct from Graph API result.varfeedFacebookFeedres, _:=session.Get("/me/feed", nil)
res.DecodeField("data.0", &feed) // read latest feed
Send a batch request
params1:=Params{
"method": fb.GET,
"relative_url": "me",
}
params2:=Params{
"method": fb.GET,
"relative_url": uint64(100002828925788),
}
results, err:=fb.BatchApi(your_access_token, params1, params2)
iferr!=nil {
// check error...return
}
// batchResult1 and batchResult2 are response for params1 and params2.batchResult1, _:=results[0].Batch()
batchResult2, _:=results[1].Batch()
// Use parsed result.varidstringres:=batchResult1.Resultres.DecodeField("id", &id)
// Use response header.contentType:=batchResult1.Header.Get("Content-Type")
Using with Google App Engine
Google App Engine provides the appengine/urlfetch package as the standard HTTP client package.
For this reason, the default client in net/http won't work.
One must explicitly set the HTTP client in Session to make it work.
import (
"appengine""appengine/urlfetch"
)
// suppose it's the AppEngine context initialized somewhere.varcontext appengine.Context// default Session object uses http.DefaultClient which is not allowed to use// in appengine. one has to create a Session and assign it a special client.seesion:=globalApp.Session("a-access-token")
session.HttpClient=urlfetch.Client(context)
// now, the session uses AppEngine HTTP client now.res, err:=session.Get("/me", nil)
// This package uses the default version which is controlled by the Facebook app setting.// change following global variable to specify a global default version.fb.Version="v3.0"// starting with Graph API v2.0; it's not allowed to get useful information without an access token.fb.Api("huan.du", GET, nil)
// it's possible to specify version per session.session:=&fb.Session{}
session.Version="v3.0"// overwrite global default.
Enable appsecret_proof
Facebook can verify Graph API Calls with appsecret_proof. It's a feature to make Graph API call more secure. See Securing Graph API Requests to know more about it.
globalApp:=fb.New("your-app-id", "your-app-secret")
// enable "appsecret_proof" for all sessions created by this app.globalApp.EnableAppsecretProof=true// all calls in this session are secured.session:=globalApp.Session("a-valid-access-token")
session.Get("/me", nil)
// it's also possible to enable/disable this feature per session.session.EnableAppsecretProof(false)
Debugging API Requests
Facebook has introduced a way to debug Graph API calls. See Debugging API Requests for more details.
This package provides both a package level and per session debug flag. Set Debug to a DEBUG_* constant to change debug mode globally, or use Session#SetDebug to change debug mode for one session.
When debug mode is turned on, use Result#DebugInfo to get DebugInfo struct from the result.
Call Result#UsageInfo to get a UsageInfo struct containing both app and page-level rate limit information from the result. More information about rate limiting can be found here.
The golang.org/x/oauth2 package can handle the Facebook OAuth2 authentication process and access token quite well. This package can work with it by setting Session#HttpClient to OAuth2's client.
import (
"golang.org/x/oauth2"
oauth2fb "golang.org/x/oauth2/facebook"
fb "github.com/huandu/facebook/v2"
)
// Get Facebook access token.conf:=&oauth2.Config{
ClientID: "AppId",
ClientSecret: "AppSecret",
RedirectURL: "CallbackURL",
Scopes: []string{"email"},
Endpoint: oauth2fb.Endpoint,
}
token, err:=conf.Exchange(oauth2.NoContext, "code")
// Create a client to manage access token life cycle.client:=conf.Client(oauth2.NoContext, token)
// Use OAuth2 client with session.session:=&fb.Session{
Version: "v2.4",
HttpClient: client,
}
// Use session.res, _:=session.Get("/me", nil)
Control timeout and cancelation with Context
The Session accept a Context.
// Create a new context.ctx, cancel:=context.WithTimeout(session.Context(), 100*time.Millisecond)
defercancel()
// Call an API with ctx.// The return value of `session.WithContext` is a shadow copy of original session and// should not be stored. It can be used only once.result, err:=session.WithContext(ctx).Get("/me", nil)
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