Get Started with Number Masking using Java

    Overview

    Phone number masking is the process of establishing a call between two parties without revealing their contact information. Many businesses often require a technique to anonymize communication between two parties involved on the platform, for example, a customer and a delivery agent on a food delivery service platform. This technique involves an intermediate phone number that acts as a proxy between the two parties on the call. In this guide, we will walk you through the implementation of number masking with the help of a Plivo number which will act as the intermediate number to connect both the parties on a call anonymously.

    Outline

    Implementation

    In this example, we will build a number masking application for a food delivery service. Through this implementation, the company can connect the customers with the delivery agents and vice versa without revealing their actual phone numbers.

    Following are the steps involved in the implementation phase:

    1. Create a Customer<->Agent phone number mapping in your application backend
    2. Create the number masking application using the Plivo Voice platform.
    3. Assign the number masking app to a Plivo number.

    Set Up Your Java Dev Environment

    You must set up and install Java(Java 1.8 or higher) and Plivo’s Java SDK to handle incoming calls and callbacks. Here’s how.

    Install Spring and Plivo Java Package using IntelliJ Idea

    • Use Spring Initializr to create a boilerplate project with Spring Boot framework.

      Create Boilerplate code

    • Choose the “Spring Web” dependency, Give the project a friendly name and click “Generate” to download the boilerplate code and open it in IntelliJ Idea.

      Boilerplate project in IntelliJ

      Note: Please set the Java target as 8 or 11.
    • Install the Plivo Java package by adding the dependency in pom.xml

        <dependency>
            <groupId>com.plivo</groupId>
            <artifactId>plivo-java</artifactId>
            <version>4.15.0</version>
        </dependency>
      

      Install Plivo package

    Create a 1:1 map with actual numbers

    • Whenever a customer places an order, the customer’s phone number is stored on your app’s database.
    • A delivery executive will be assigned for that order, and the agent’s number is also stored on your database and mapped with the customer’s number. For example,
        Customer's Number		<->		Agent's Number
        1-415-666-7777					1-415-666-7778
      
    • In this guide, we have created a sample mapping data in src/main/resources/application.properties file like below:
        spring.main.banner-mode=off
        spring.output.ansi.enabled=ALWAYS
        logging.pattern.console=%clr(%d{yy-MM-dd E HH:mm:ss.SSS}){blue} %clr(%-5p) %clr(%logger{0}){blue} %clr(%m){faint}%n
      
        number.map={"14156667777":"14156667778", "14156667779":"14156667780", "14156667781":"14156667782"}
      

    Create a Spring App for Number Masking

    Now, locate the NumberMaskingApplication.java file in the src/main/java/com.example.NumberMasking/ folder and paste the following code.

    Note: Here, the demo application name is NumberMaskingApplication.java because the friendly name provided in the Spring Initializr was NumberMasking.
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    package com.example.NumberMasking;
    
    import com.plivo.api.exceptions.PlivoXmlException;
    import com.plivo.api.xml.Dial;
    import com.plivo.api.xml.Response;
    import com.plivo.api.xml.Number;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.web.bind.annotation.*;
    import com.google.common.collect.HashBiMap;
    import java.util.Map;
    
    @SpringBootApplication
    @RestController
    public class NumberMaskingApplication {
    
    	@Value("#{${number.map}}")
    	Map<String, String> CustomerAgentMap;
    
    	public static void main(String[] args) {
    		SpringApplication.run(NumberMaskingApplication.class, args);
    	}
    
    	// Handle incoming calls to a Plivo number, connect agent with customer and vice versa without revealing their actual phone numbers.
    	@RequestMapping(value = "/number_masking/", produces = { "application/xml" }, method = { RequestMethod.GET, RequestMethod.POST })
    	public Response HandleIncoming(@RequestParam("From") String FromNumber, @RequestParam("To") String ToNumber)
    			throws PlivoXmlException {
    		Map<String, String> AgentCustomerMap = HashBiMap.create(CustomerAgentMap).inverse();
    		Response response = new Response();
    		if(CustomerAgentMap.containsKey(FromNumber)) { // To check if the Customer's number is existing in the Customer-Agent mapping
    			var DestNumber =  CustomerAgentMap.get(FromNumber); // This will assign the Value from the customer-agent map to DestNumber variable
    			response.children(new Dial()
    					.callerId(ToNumber) // Plivo number will be used as the caller ID for the call towards Agent
    					.children(new Number(DestNumber)));
    		}
    		else if (AgentCustomerMap.containsKey(FromNumber)) { // To check if the Agent's number is existing in the Customer-Agent mapping
    			var DestNumber =  AgentCustomerMap.get(FromNumber); // This will assign the Key from the customer-agent map to DestNumber variable
    			response.children(new Dial()
    					.callerId(ToNumber) // Plivo number will be used as the caller ID for the call towards Customer
    					.children(new Number(DestNumber)));
    		}
    		System.out.println(response.toXmlString());
    		return response;
    	}
    }
    

    Save the file and run it.

    Number Masking

    And you should see your basic server app in action on http://localhost:8080/number_masking/

    Exposing your local server to the internet

    To receive Incoming Calls and to handle callbacks, your local server should be able to connect with Plivo API service, Ngrok is a tunneling software used to expose a web server running on your local machine to the internet. Using Ngrok you can set webhooks which can talk to Plivo server.

    ngrok block diagram

    You can download and install ngrok from here. Follow the detailed configuration instructions to get started.

    Run ngrok on the port which currently hosts your application. For example, if your port number is 8080, run the following command:

    ./ngrok http 8080
    

    This will give you a UI with links that look like ngrok.io/* which you can use to access your local server using the public network.

    Sample ngrok CLI

    • If the incoming call to your Plivo number is from one of the phone numbers of the customer in the Customer <-> Agent Map, for example, if the caller number is “14156667777” then the XML response to process the incoming call will be as below, you can check the XML document in your browser.

      XML Document - Customer Calls Agent

    • If the incoming call to your Plivo number is from one of the phone numbers of the agent in the Customer <-> Agent Map, for example, if the caller number is “14156667778” then the XML response to process the incoming call will be as below, you can check the XML document in your browser.

      XML Document - Agent Calls Customer

    Create a Plivo Application

    1. Create an Application by visiting the Application Page and click on New Application or by using Plivo’s Application API.
    2. Give your application a name. Let’s call it Phone IVR. Enter your server URL (e.g., https://349f5c931df4.ngrok.io/number_masking/) in the Answer URL field and set the method as GET. See our Application API docs to learn how to modify your application through our APIs.
    3. Click on Create to save your application.

      Create Application - Number Masking

    Assign a Plivo number to your app

    1. Navigate to the Numbers page and select the phone number you want to use for this app.
    2. Select Phone IVR (name of the app) from the Plivo App dropdown list.
    3. Click on ‘Update Number’ to save.

      Assign Application - Number Masking

    Test and validate

    To test how “Number Masking” works, you need two mobile numbers. You can set one of your mobile numbers as a customer and another one as an agent in the customer: agent mapping data in the config file and make a call to your Plivo phone number. If you call from “mobile number 1” to the Plivo number, you will see that the call is forwarded to your “mobile number2” with the Plivo number as the caller ID. The same setup will work for calls from “mobile number2” to “mobile number1” with the Plivo number as the caller ID.