The backend design for Pledger.io

The REST-api is the main part of the application. This is a Java base web application that contains all the business logic for Pledger.io. The user interface is bundled into the application by the Deployment setup.

Used tooling

This part of Pledger.io is build using the following tooling:

Gradle, used as the build tool.
Micronaut framework, used as the DI and API framework.
LangChain4j, used as the engine to interact with Vector stores and LLM implementations.

Rest design

The REST interface is designed contract-first. This means that all APIs are designed in an Open API Specification file and interfaces are generated using Micronaut.

The code is generated at compile time, and each module implements a small part of the REST interface.

Internal design

Enforcement of design

When contributing Pledger.io keep in mind that there are unit tests that enforce the domain and module structure that is detailed on this page.

This is achieved by some ArchUnit tests that validate modules do not access modules they are not allowed to and ensure that there is no access to layers inside modules that are undesired. If a case ever arises where these rules need to be re-evaluated, always contact the core developer team first.

Modular design

The REST-api is designed to be a stateless application. The application is split up in several modules, where each module can depend on other modules. This is done to allow the application to be designed around a use case, like personal budgeting or small organizations.

Module	Dependencies	Description
Core	-	The base module for the entire Pledger.io application.
Banking	Core	The module contains all logic regarding the transaction management and account management.
Classification	Core Banking	Contains a system to categorize things in Pledger.io.
Budget	Core Banking	Contains the logic allowing users to budget their spending.
Contract	Core Banking	Contains the logic allowing users to manage any contracts they have for spending.
Suggestions	Core Banking Classification Budget	Contains logic to suggest changes to transactions, either using pre-defined rules or AI.
Exporter	Core Banking Classification Budget	Contains the logic to import and export all information from a users account.

Module

Dependencies

Description

Core

The base module for the entire Pledger.io application.

Banking

Core

The module contains all logic regarding the transaction management and account management.

Classification

Core
Banking

Contains a system to categorize things in Pledger.io.

Budget

Core
Banking

Contains the logic allowing users to budget their spending.

Contract

Core
Banking

Contains the logic allowing users to manage any contracts they have for spending.

Suggestions

Core
Banking
Classification
Budget

Contains logic to suggest changes to transactions, either using pre-defined rules or AI.

Exporter

Core
Banking
Classification
Budget

Contains the logic to import and export all information from a users account.

Architecture of each module

Each of the modules has a similar structure. This is constructed as follows:

adapters, where the incoming and outgoing APIs are located for that module.
domain, where the modules internal business logic resides.

Inside the domain the database is abstracted away in the jpa package, as well as the commands and models that allow for interaction with the public facing adapter of the module.

The service package in the module hosts the scheduled jobs or core business logic for the module.

Used tooling
Rest design
Internal design