Spring Boot Rest Example

I made this project to know more about how to make a REST application with Spring boot (MVC + Data). The objective of this small project was to design a RESTful web service storing transactions and returning information about them.

Quick start

To build and run this Spring Boot application use:

mvn spring:boot-run

Beside the integration tests, you can get a quick overview of the functionalities by using a bash script (you need to install curl)

sh ./src/test/resources/test.sh

It should give the following output

$ sh ./src/test/resources/test.sh
PUT /transactionservice/transaction/10 { amount: 5000, type: cars } =>
{"status":"ok"}

PUT /transactionservice/transaction/11 { amount: 10000, type: shopping, parent_id: 10 } =>
{"status":"ok"}

GET /transactionservice/types/cars =>
[10]

GET /transactionservice/sum/10 =>
{"sum":15000.0}

GET /transactionservice/sum/11 =>
{"sum":10000.0}

PUT /transactionservice/transaction/10 { amount: 5000, type: cars, parent_id: 11 } =>
{"status":"error"}

DELETE /transactionservice/transaction/11 =>


DELETE /transactionservice/transaction/10 =>

The internal state of the H2 database can be checked through the H2 console http://localhost:8080/h2-console/

Design choices

In this project, transactions are represented as trees (cf /transactionservice/sum/:id for application examples) even if it is not really close to what we would have in real banking systems.

The objective was to allow to demonstrate how to design a robust system, in this case by detecting requests that would cause an inconsistent state of the system, for example by introducing cycles in the transaction tree, thus making it into a graph.

I chose H2 with disk persistence for database but the use of Liquibase and Spring Data allow to use any other base just by adding a new Spring profile and its corresponding YAML configuration file (in src/resources/config).

The base can be cleaned by deleting the target folder with mvn clean. In order to allow to run the integration tests while the application is running, I wrote a specific configuration file to deploy the application or another port (10344) and by using an in-memory H2 base.

Discussion

The code is very much inspired by the work I did using the JHipster project (https://jhipster.github.io/) in the past months. This time I decided to not use the generator at all, but to start an application from scratch, while still keeping a similar structure.

In order to learn new things, I decided to use the Jackson annotation @JsonView to allow for discrepancies between the model entities and the JSON format used in the REST requests and also wrapper objects for the PUT and POST requests.

I also decided to have rather comprehensive integratioon tests, thus not only testing the model classes but also the REST services themselves (cf org.jbourdon.springRestExample.web.rest.TransactionResourceIntTest for more details)