Embedding the MongoDB Connector into the server

In our previous guide, we launched our sample GitHub project demonstrating the basics of using Flexmonster MongoDB Connector. The information from that guide is considered a prerequisite for this tutorial, it is highly recommended that you complete the previous guide before starting this one.

This tutorial describes how to embed the Connector into a server.

To fetch data from a database and pass it to the component, the Connector needs a mediator between itself and Flexmonster. Your server acts as this mediator and its task is to handle Flexmonster’s requests and to pass them to the Connector in the correct format. The server has to be configured properly to complete this task.

All requests have the type property in the request body. There are 4 types of requests that can be distinguished by the URL path and type value:

• <url>/handshake – The first (handshake) request to establish a connection between the client and server.
• <url>/fields – Request for all fields with their types (i.e., meta-object or schema).
• <url>/members – Request for all members of a field.
• <url>/select – Request for the data.

The value of type will always be the same as the endpoint name, e.g., when a request is sent to <url>/fields, the value of type is "fields".

The Connector has three methods to handle /fields, /members, and /select requests. See the documentation to learn more about these methods.

The following guide will walk you through the process of server configuration.

Step 1. Embed the component into your webpage

If Flexmonster is not yet embedded, set up an empty component in your webpage:

let pivot = new Flexmonster({
  container: "pivotContainer",
  componentFolder: "node_modules/flexmonster/",
  toolbar: true
});

<FlexmonsterReact.Pivot
 toolbar={true}
/>

<fm-pivot
 [toolbar]="true">
</fm-pivot>

<Pivot
 toolbar
/>

In the next steps, we will start configuring the server.

Step 2. Create a simple server

We will now focus on the server part of our project. 

First, let's create a simple server using Express.js. If you already have a server, jump to Step 3. Create a separate module for the request routing.

Follow the steps below to get a simple server application:

Step 2.1. Create a folder for the server and run the npm init command there to generate the package.json file.

Step 2.2. The server needs the express, cors, and body-parser packages. Install them with npm:

npm install express

npm install cors

npm install body-parser

Step 2.3. Then, create a simple server in a .js file (e.g., server.js):

const express = require("express");
var cors = require("cors");
var bodyParser = require("body-parser");

const app = express();

app.use(cors());
app.use(bodyParser.json());

var port = 9204;
app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`)
});

Step 3. Create a separate module for the request routing

All the request routing will be implemented in a separate .js file (e.g., mongo.js).

At this step, include the .js file (i.e., mongo.js) into your server. All the requests coming to <url> will be handled by this separate module (in this case, the <url>/mongo path is used):

app.use('/mongo', require('./mongo.js'));

All the requests sent to <url> (in this case,<url>/mongo) will now be processed by the mongo module.

However, since we haven’t yet defined the mongo.js file properly, the code won’t work just yet.

Note If Flexmonster Pivot is running on a different server, enable CORS.

Step 4. Install packages for the mongo.js module

Install Flexmonster MongoDB Connector and the MongoDB driver:

npm install flexmonster-mongo-connector
npm install mongodb

Now it's time to configure the mongo.js module.

Step 5. Configure the mongo.js module

Configure the mongo.js module in three steps:

Step 5.1. In the JavaScript file mentioned in the previous step (i.e., mongo.js), include the following libraries:

const mongo = require('express').Router();
const mongodb = require("mongodb");
const fm_mongo_connector = require("flexmonster-mongo-connector");

Step 5.2. Then set up a connection with your MongoDB database and define the Connector:

let dbo = null;
let _apiReference = null; // it’ll be the Connector instance
 
// Define the config for the Connector
let config = {
  cacheEnabled: true,
  cacheMemoryLimit: 100,
  cacheTimeToLive: 120,
  logsEnabled: true
};

mongodb.MongoClient.connect(
  "mongodb://read:only@olap.flexmonster.com:27017", 
  {
    useNewUrlParser: true,
    useUnifiedTopology: true 
  }, 
  (err, db) => {
    if (err)
      throw err;
    dbo = db.db("flexmonster");
    // Pass the config to the Connector 
    _apiReference = new fm_mongo_connector.MongoDataAPI(config);
  }
); 

To learn more about the Connector’s config, see this guide: Configuring the Connector.

Step 5.3. Export the mongo module so the server can use it:

// requests handling functions will appear here
module.exports = mongo;

This module can now connect to your MongoDB database, but it does not handle the Flexmonster Pivot requests. In the next steps, we will handle all Flexmonster requests.

Step 6. Handle the /handshake request

First, Flexmonster sends the /handshake request to establish communication with the server. The component includes its version in the request and expects a response with the custom data source API version implemented by the server.

Here is an example of how to handle the /handshake request:

mongo.post("/handshake", async (req, res) => {
  try {
    res.json({ version: _apiReference.API_VERSION });
  } catch (err) {
    handleError(err, res);
  }
});

_apiReference.API_VERSION contains the custom data source API version implemented by the MongoDB Connector.

Step 7. Handle the /fields request

The next request that needs to be handled is a /fields request; it is sent to <url>/fields. It can be handled using the getSchema method:

mongo.post("/fields", async (req, res) => {
  try {
    const result = await _apiReference.getSchema(dbo, req.body.index);
    res.json(result);
  } catch (err) {
    //your error handler
  }
});

When Flexmonster Pivot successfully receives a response to the /fields request, it shows the Field List with all of the available fields.

Step 8. Handle the /members request

The next request to handle is the request for the field’s members that is sent to <url>/members.

Ways to handle the /members request depend on whether multilevel hierarchies are configured on the client or not.

mongo.post("/members", async (req, res) => {
  try {
    const result = await _apiReference.getMembers(
      dbo,
      req.body.index, 
      { field: req.body.field }, 
      { page: req.body.page, pageToken: req.body.pageToken }
    );
    res.json(result);
  } catch (err) {
    //your error handler
  }
});

mongo.post("/members", async (req, res) => {
  try {
    const result = await _apiReference.getMembers(
      dbo,
      req.body.index, 
      { field: req.body.field, filter: req.body.filter },
      { page: req.body.page, pageToken: req.body.pageToken }
    );
    res.json(result);
  } catch (err) {
    //your error handler
  }
});

{ field: req.body.field, filter: req.body.filter },

When Flexmonster Pivot successfully receives the response to this request, you will be able to select a string field for rows or for columns and retrieve its members.

Step 9. Handle the /select request

When a field is selected for rows or columns and a numeric field is selected for measures in the Field List, the /select request for the pivot table is sent to the endpoint <url>/select. It can be handled using the getSelectResult method:

mongo.post("/select", async (req, res) => {
  try {
    const result = await _apiReference.getSelectResult(
      dbo, req.body.index, req.body.query,
      { page: req.body.page, pageToken: req.body.pageToken });
    res.json(result);
  } catch (err) {
    //your error handler
  }
});

When Flexmonster successfully receives the response to this kind of /select request, a pivot table with the received data is shown.

Note The /select requests for the flat table and the drill-through view can also be handled using the getSelectResult method.

Step 10. Run the server

Run your server with the following command:

node server.js

Step 11. Configure the report

Now it’s time to configure the pivot table on the webpage. In report.dataSource, define these parameters to connect to your server:

let pivot = new Flexmonster({
  container: "pivotContainer",
  componentFolder: "node_modules/flexmonster/",
  toolbar: true,
  report: {
    dataSource: {
      type: "api",
      url: "<url>",
      index: "your-collection-name"
    }
  }
}); 

Here, url is the path to your API endpoints (e.g., "http://localhost:9204/mongo"), and index is your collection’s name. index will be sent with every request.

Open your HTML page in the browser to see the result - the pivot table with data from your MongoDB database is shown.

What’s next?

• How to configure the MongoDB Connector
• How to configure which data subset is shown
• How to specify functionality available to users
• How to define number formatting
• How to define a format for date and time