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Chat Application backend

About The Project

This is the backend implementation for chat application through EDC. The server connects to the below entities for a successful chat flow:

  • a Business Partner's EDC to establish a two-way communication.
  • a Postgres database to store other Business Partners' information and chat history.
  • a simple UI to send messages to and receive messages from other Business Partners.

NOTE:

  • When the backend application starts, it will create the Asset with id edc-chat-app, Policy, and Contract Definition. Please refer EDCService.initializePreEdcProcess() for more details
  • However, if the assetId as an edc-chat-app is already in the edc database, it’ll skip this process.
  • Policy is created to check Membership credential of participant. Each participate needs to present Membership credential to start data negotiation.

Packages Overview

The backend application consists of the below packages:

  • dao: Contains the database entities and their JPA repositories
  • edc: This package contains a client to communicate with another EDC, services to create assets, policies, negotiate contract,data transfer etc.
  • service: Houses the services that implement the application's business logic
  • utils: The utils package contains application configurations, constants, validation methods, etc.
  • web: Houses the main application and the REST controllers for communicating with the server
    • apidocs: This child package contains the documentation of the APIs in the web package and is used in generating the OpenAPI specification

WebSocket

This application uses WebSocket connection to facilitate simultaneous transfer of messages between frontend and the server. The WebSocketConfig.java implements WebSocketMessageBrokerConfigurer interface to configure below properties:

  • STOMP Endpoint: This endpoint is added to the StompEndpointRegistry for the clients to look up and connect to the WebSocket.
  • Message Broker destinations: The client subscribes to these prefixes for receiving messages from the server.
  • Application Destination Prefixes: The client sends messages to the server using these API prefixes.
  • User Destination Prefix: This prefix is used while establishing a unique session between the client and the server.

How to deploy the backend application :

Pre-requisite to start backend Application

  • EDC
  • Wallet Stub
  • Postgres Database

Local setup :

  • Build the Project Open the project terminal and run: 
    ./gradlew clean build
  • For locally deploy EDC, Postgres, wallet using Docker, please refer : README.md
  • After deployment, set the following environment variables:
Env Name Description
CHAT_DB Database host
DB_HOST Database name (create if it does not exist)
DB_USER Database username
DB_PASS Database password
AUTH_CODE EDC AuthCode
ASSET_ID Asset ID to configure for communication
POLICY_ID Asset Policy ID
CONTRACT_ID Asset Contract Definition ID
EDC_URL EDC Base Management URL
APP_PORT Application running port
BPN Application owner's bpn
AGREEMENT_WAIT_MILLI Wait time in millisecond till contract finalized
AGREEMENT_RETRY_LIMIT Max retry check for contract to be finalized
APP_HOST_URL Application host url to add in asset
  • Run the application by executing the following command: 
    ./gradlew bootRun

Database

For data migration, we use Liquibase. So when the application starts or restarts, the data will already be added or updated.

Database Table Documentation

business_partner Table

Column Name Data Type Constraints Default Value Description
id UUID PRIMARY KEY, NOT NULL uuid_generate_v4() Unique identifier for the record.
name VARCHAR(100) NOT NULL None Name of the business partner.
bpn VARCHAR(50) NOT NULL None Business Partner Number.
edc_url VARCHAR(250) NOT NULL None URL for EDC communication.
created_at TIMESTAMP(6) NULL NOW() Timestamp when the record was created.
updated_at TIMESTAMP(6) NULL NOW() Timestamp when the record was last updated.

chat_messages Table

Column Name Data Type Constraints Default Value Description
id SERIAL PRIMARY KEY Auto-increment Unique identifier for the record
partner_bpn VARCHAR(255) NOT NULL None BPN of the partner
message TEXT NOT NULL None The chat message content
self_owner BOOLEAN NULL None Indicates whether the message is self-owned
is_chat_success BOOLEAN NULL None Indicates if the chat was successful
negotiation_id VARCHAR(255) NULL None Contract negotiation id
agreement_id VARCHAR(255) NULL None Contract agreement id
transfer_id VARCHAR(255) NULL None Transfer id
error_detail TEXT NULL None Error details if any of the EDC process fails
created_at TIMESTAMP(6) NULL NOW() Timestamp when the message was created

edc_offer_details Table

Column Name Data Type Constraints Default Value Description
id SERIAL PRIMARY KEY Auto-increment Unique identifier for the record.
receiver_bpn VARCHAR(255) NOT NULL None BPN of the receiver.
offer_id VARCHAR(255) NOT NULL None Policy offer id.
asset_id VARCHAR(255) NULL None Receiver's asset id.
created_at TIMESTAMP(6) NULL NOW() Timestamp when the message was created.