Backend

Backend system Architecture

DB and backend are separate services in docker compose.

Initialization directions

1. Start MySQL server: mysql.server start
2. docker compose up --build (this will initialize database on local machine through volume)

WebSocket Chat Feature

Overview

This project includes a WebSocket-based real-time chat feature, allowing users to send and receive messages instantly. The chat system leverages Spring WebSocket and STOMP for message handling.

Key Components

• WebSocket Configuration: Configures the WebSocket endpoints and message broker.
• WebSocket Controller: Handles incoming WebSocket messages and routes them to the appropriate users.
• Message Service: Manages message persistence and retrieval.

Configuration

File: src/main/java/com/nexus/api/config/WebSocketConfig.java

The WebSocket configuration includes:

• Setting up the endpoint at /ws with SockJS fallback.
• Configuring message broker with /queue for user-specific destinations and /app for application-specific destinations.
• Allowing origins using setAllowedOriginPatterns to handle CORS issues.

Controller

File: src/main/java/com/nexus/api/web/WebSocketController.java

The WebSocket controller:

• Receives and processes messages sent to /app/sendMessage.
• Validates and retrieves sender and receiver information from the database.
• Saves the message to the database.
• Sends the message to the recipient's WebSocket queue.

Common Issues and Solutions

Issue: CORS Policy Blocking Requests

Problem: During development, requests to the WebSocket endpoint were blocked by the browser due to CORS policy.

Solution:

• Initially, using .setAllowedOrigins("*") did not work because it conflicts with allowCredentials.
• Resolved by using .setAllowedOriginPatterns("*"), which allows flexible origin patterns including wildcards.

Discover Feature

Overview

The Discover feature allows users to discover other individual or organization accounts based on their zip code and a specified distance radius. It uses a third-party API (ZipCodeAPI) to find all zip codes within a given radius and then fetches eligible accounts from those locations.

Key Components

• Discover Endpoint: Allows clients to request account discovery based on location and distance.
• Account Service: Handles the business logic for finding and returning eligible accounts.
• Zip Code Service: Communicates with the ZipCodeAPI to get zip codes within a specified radius.

Configuration

File: src/main/java/com/nexus/api/web/AccountController.java

The Discover endpoint:

• Accepts zipCode, distance, and loggedInAccountId as request parameters.
• Fetches zip codes within the radius using ZipCodeService.
• Finds eligible accounts within the retrieved zip codes using AccountService.
• Filters out the logged-in account from the results.
• Returns a random eligible account.

File: src/main/java/com/nexus/api/business/AccountService.java

The Account service:

• Contains methods to find zip codes within a radius, find accounts by zip codes, and return a random eligible account.
• Ensures the logged-in account is excluded from the discovery results.

File: src/main/java/com/nexus/api/business/ZipCodeService.java

The Zip Code service:

• Communicates with the ZipCodeAPI to retrieve zip codes within a specified radius.
• Sends a POST request to the ZipCodeAPI with the base zip code and distance.
• Parses and returns the list of zip codes from the API response.

Usage Example

To discover new accounts, clients can send a GET request to the discover endpoint: