Facebook – Reviews (Graph API)

前言

企业网站经常需要放 customer reviews 来增加 conversion. 常见的 Reviews 平台有 Facebook Reviews 和 Google Reviews.

这篇, 我将介绍如果通过 ASP.NET Core calling Facebook Graph API 来获取 Facebook Page 的 Reviews.

Preparation

首先要有 Facebook Page, Facebook Developer Account 和 Facebook App Development.

1. Get Facebook Page ID

上面这招好像过时了, 最新的版本找不到了....

目前找到另一招, 到 meta business 里面看 URL, 先用着呗

2. Create App

登入 Facebook 然后到 https://developers.facebook.com

点击 My App

点击 Create App

选择 type: None. 不要选 Business 哦 (Business 需要官方认证才能获取许多 permission, 很麻烦的... 我用 none 就足够了)

写 App 名字

Settings > Basic > 填写 Privacy Policy URL > Save changes

App Review > Permission and Features > Get advanced access (email, public_profile)

Checkup Get started > agree and next 到底

Live

2. Get App ID and App Secret

Page Access Token

参考: Docs – Access Tokens

在发送 API 的时候需要有 Page Access Token

Facebook 的 Access Token 有分 4 种:

• Short-lived User Access Token (1 hour)
• Long-lived User Access Token (60 days)
• Short-lived Page Access Token (1 hour)
• Long-lived Page Access Token (never expired)

要拿 Page Reviews 需要用到 Page Access Token. 但要拿到 Page Access Token 必须先拿到 User Access Token.

拿 User Access Token 有 2 个方法. 第一个就是 Facebook Login Dialog. 第二个是用 Graph Explorer tool

我的需求比较简单, backend daily server task 去拿新的 reviews 更新数据库.

所以会使用 Graph Explorer tool 去拿 Long-lived Page Access Token. 往后就在 server side 发 API 可以了.

Short-lived User Access Token

使用 Graph Explorer tool (需要 Facebook Developer Account 和 Facebook App Development)

然后会弹出 Facebook Login Dialog, 登入就可以了

然后就拿到 Short-lived User Access Token 了.

注: Page Reviews 需要下面这些 Permissions (不同 API 权限不一样, 每次添加 Permission 都需要重新 Generate Access Token 哦)

user_photos 好事不需要也行。

Long-lived User Access Token

有了 Short-lived 才能拿到 Long-lived. 接着我们可以用 Postman 来完成

GET URL: https://graph.facebook.com/oauth/access_token

query params:

grant_type : fb_exchange_token

client_id : App ID (上面有提到了)

client_secret : App Secret (上面有提到了)

fb_exchange_token : xxxxxx (这里放 Short-lived User Access Token)

Long-lived Page Access Token

有了 Long-lived User Access Token 才能拿到 Long-lived Page Access Token.

GET URL: https://graph.facebook.com/2019305211658271 (2019305211658271... 是 Facebook Page ID)

query params:

fields : access_token

access_token : xxxxxx (这里放 Long-lived User Access Token)

至此我们就拿到了可以长期使用的 Long-lived Page Access Token 了.

Reviews Graph API

参考: Docs – Page Ratings

GET URL : https://graph.facebook.com/2019305211658271/ratings

query params:

access_token : xxxxxx (这里放 Long-lived Page Access Token)

fields : created_time,recommendation_type,review_text,reviewer,has_rating,rating,has_review

效果

Facebook Reviews 不一定有 rating, 用户可以选择打分或者写 review, 或者 2 个一起.

p.s. Reviews API 视乎不支持 filter. 以后才研究呗. 参考1, 参考2 TODO...

p.s. created_time 的格式挺奇葩的, 许多人都有意见, C# 也无法直接 parse to DateTimeOffset,

解决方法是添加 query param date_format : U, 这样它会返回 int 从 1970 年的秒数 (不是毫秒哦), 之后我们就可以自己 Convert 到想要的格式了.

p.s. 默认返回 25 条资料，可以通过 query param "limit=525" 去限制或者扩大，最多可以一次输出 525 条。

ASP.NET Core 调用 Reviews Graph API

public class TestPageModel : PageModel
{
    private readonly IHttpClientFactory _httpClientFactory;

    public TestPageModel(
        IHttpClientFactory httpClientFactory
    )
    {
        _httpClientFactory = httpClientFactory;
    }
    public async Task OnGet()
    {
        var pageId = "2019305211658271";
        var accessToken = "xxxxxx";

        var queryBuilder = new QueryBuilder();
        queryBuilder.Add("access_token", accessToken);
        queryBuilder.Add("fields", "created_time,recommendation_type,review_text,reviewer,has_rating,rating,has_review");
        var queryString = queryBuilder.ToQueryString().Value!;

        var httpRequestMessage = new HttpRequestMessage
        {
            RequestUri = new Uri($"https://graph.facebook.com/{pageId}/ratings{queryString}"),
            Method = HttpMethod.Get,
        };
        httpRequestMessage.Headers.Add("Accept", "application/json; charset=utf-8");

        var httpClient = _httpClientFactory.CreateClient();
        var response = await httpClient.SendAsync(httpRequestMessage);
        if (response.IsSuccessStatusCode)
        {
            var json = await response.Content.ReadAsStringAsync();
        }
    }
}

获取 Reviewer Picture

参考: Docs – User Picture

Reviews API 只能拿到 reviewer name 和 id 没有 picture. 想拿 picture 需要 call 另一个 API.

GET URL : https://graph.facebook.com/5431925970230375/picture (5431925970230375 是 reviewer id)

query params:

access_token : xxxxxx (这里放 Long-lived Page Access Token)

width : 320 (默认是 50px 很小, 大一号是 320px)

效果

注: 它返回的是 byte 哦, Content-Type 是 image/jpeg

ASP.NET Core 调用 Picture Graph API

public class TestPageModel : PageModel
{
    private readonly IHttpClientFactory _httpClientFactory;

    public TestPageModel(
        IHttpClientFactory httpClientFactory
    )
    {
        _httpClientFactory = httpClientFactory;
    }
    public async Task OnGet()
    {
        var userId = "5431925970230375";
        var accessToken = "xxxxx";

        var queryBuilder = new QueryBuilder();
        queryBuilder.Add("access_token", accessToken);
        queryBuilder.Add("width", "320");
        var queryString = queryBuilder.ToQueryString().Value!;

        var httpRequestMessage = new HttpRequestMessage
        {
            RequestUri = new Uri($"https://graph.facebook.com/{userId}/picture{queryString}"),
            Method = HttpMethod.Get,
        };
        httpRequestMessage.Headers.Add("Accept", "image/jpeg");

        var httpClient = _httpClientFactory.CreateClient();
        var response = await httpClient.SendAsync(httpRequestMessage);
        if (response.IsSuccessStatusCode)
        {
            var buffer = await response.Content.ReadAsByteArrayAsync();
            using var fileStream = System.IO.File.Create("reviewer-avatar.jpg", buffer.Length);
            await fileStream.WriteAsync(buffer);
            fileStream.Flush();
        }
    }
}

错误处理

比如 Page ID 不正确, 它会返回 400 bad request, JSON 是一个 error message.

如果有设置 Accept header 的话, 一定要加上 application/json 来处理错误哦

比如

Reviews API = Accept : application/json; charset=UTF-8

Picture API = Accept : image/jpeg, application/json (注: 我试过 + charset=UTF-8 但是不行...不知道为什么)

总结

这篇介绍了如何通过 ASP.NET Core 调用 Graph API 获取 Page Reviews 和 Reviewer Picture.

第一步是基本 setup (Facebook page, Developer account, App)

第二步是获取永久可用的 Page Access Token, 这样 server 就可以一直去拿最新的 Reviews.

第三步是调用 Graph API 获取 Reviews 和 Reviewer Picture.

题外话 – 获取 Facebook Page Post Content

这主题应该开多一篇介绍的，但我还没有准备好，所以先记入在这里呗。