[Firebase] Messaging 推播訊息 # 2 利用Nodejs發送推播

Firebase 推播訊息 的第二篇文章是在說明當 Firebase 專案建立完成之後，如何利用Nodejs和專案裡的金鑰將message推播出去

本篇會先介紹如何建立一個Nodejs專案，再介紹如何透過程式將訊息推播出去。

1. 首先建立一個sendMsg的資料夾

mkdir sendMsg

cd sendMsg
npm init

3. 接下來一直按enter會出現下列command，最後輸入yes

This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

See `npm help init` for definitive documentation on these fields
and exactly what they do.

Use `npm install <pkg>` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
package name: (sendmsg)
version: (1.0.0)
description:
entry point: (index.js)
test command:
git repository:
keywords:
author:
license: (ISC)
About to write to D:\exampleProject\sendMsg\package.json:

{
  "name": "sendmsg",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}


Is this OK? (yes)

4. 再來直接在command line 直接輸入code . ，vscode會直接開啟資料夾，或是開啟vscode再引入sendMsg資料夾也可以，目的是要開啟sendMsg資料夾

5. 在sendMsg資料夾內新增index.js

6. 再新增key.json，將剛才firebase的私密金鑰內容完整的貼進來

7. 再來我們要在資料夾內安裝需要的npm

npm i https googleapis -s

8. 之後在index.js輸入下列程式碼

const https = require('https')
var {google} = require('googleapis')

const key = require('./key.json')
const PROJECT_ID = key.project_id;
const HOST = 'fcm.googleapis.com';
const PATH = '/v1/projects/' + PROJECT_ID + '/messages:send';
const MESSAGING_SCOPE = 'https://www.googleapis.com/auth/firebase.messaging';
const SCOPES = [MESSAGING_SCOPE];



function getAccessToken() {
    return new Promise(function(resolve, reject) {
      const jwtClient = new google.auth.JWT(
        key.client_email,
        null,
        key.private_key,
        SCOPES,
        null
      )
      jwtClient.authorize(function(err, tokens) {
        if (err) {
          reject(err);
          return;
        }
        resolve(tokens.access_token);
      });
    });
  }
  
 /**
 * Send HTTP request to FCM with given message.
 *
 * @param {object} fcmMessage will make up the body of the request.
 */
function sendFcmMessage (fcmMessage) {
    getAccessToken().then(function(accessToken) {
      const options = {
        hostname: HOST,
        path: PATH,
        method: 'POST',
        // [START use_access_token]
        headers: {
          'Authorization': 'Bearer ' + accessToken
        }
        // [END use_access_token]
      };
  
      const request = https.request(options, function(resp) {
        resp.setEncoding('utf8');
        resp.on('data', function(data) {
          console.log('Message sent to Firebase for delivery, response:');
          console.log(data);
        });
      });
  
      request.on('error', function(err) {
        console.log('Unable to send message to Firebase');
        console.log(err);
      });
  
      request.write(JSON.stringify(fcmMessage));
      request.end();
    });
  }

   /**
   * Construct a JSON object that will be used to define the
   * common parts of a notification message that will be sent
   * to any app instance subscribed to the news topic.
   */
   function buildCommonMessage() {
    return {
      'message': {
        'topic': 'all',
        'notification': {
          'title': 'FCM Notification',
          'body': 'Notification from FCM',
        }
      }
    };
  }


  const commonMessage = buildCommonMessage();
  console.log('FCM request body for message using common notification object:');
  console.log(JSON.stringify(commonMessage, null, 2));
  sendFcmMessage(buildCommonMessage());

9. 完成之後，要用node 去執行index.js的程式發送message，在command line下輸入：

node index.js

10. command line就會出現

FCM request body for message using common notification object:
{
  "message": {
    "topic": "all",
    "notification": {
      "title": "FCM Notification",
      "body": "Notification from FCM",
    }
  }
}
Message sent to Firebase for delivery, response:
{
  "name": "projects/test-18a9a/messages/2560468080093694458"
}

11. 依照firebase官方文件，response出現下列文字就是正常可以發送

{
  "name": "projects/test-18a9a/messages/2560468080093694458"
}

參考文件

Firebase Cloud Messaging
The server side of Firebase Cloud Messaging consists of two components: The FCM backend provided by Google. Your app…firebase.google.com

REST Resource: projects.messages | Firebase Cloud Messaging REST API
Discover solutions for use cases in your apps and businessesfirebase.google.com

就如之前所說明的，此方式是針對topic推播訊息，如果需要針對應用程式，就要先將FCM TOKEN全部記錄下來。