Java - TP5

Spring Boot Application

Author

Ludovic Deneuville

Ideas of Questions:

Use Stream
Check if age >=0
Use an Enum for gender

Objectives

The aim is to develop a Spring Boot application:

using layered programming
creating new functionalities
coding some API endpoints

The principle will be the same as what was done in IT project 2A.

1 Before you start

When you’ve finished, don’t forget to delete your service.

After each part, create a commit and push your code to the remote repository.

1.1 Launch service VSCode Java

We’re developing an API for public Internet access, which requires us to expose our application through a specific port (5000).

Restart the service from the last lab or Launch a new service VScode-Java
During container startup, copy the link where your application will be exposed (port 5000)
- It looks like : https://user-<sspcloud_username>-<6digits_number>-user<optional: -5000>.user.lab.sspcloud.fr/

Warning

If your service authorises the opening of another port (ex: 5000) on the Internet, you will need to use the same port to launch your Spring Boot application (application.yml file).

1.2 Update your repository

Perhaps the repository used as a template has been updated since the last practical session.

Follow the commands given in Lab 2 to update your repository

1.3 Open Folder

In VSCode :

File > Open Folder > tp5
- or using: code-server ~/work/ENSAI-2A-Java-TP/tp5/

tp5 must be the root folder in your explorer.

1.4 When you’ve finished

Save your work using git
Pause or Delete your service

1.5 Compile and run

If necessary in the terminal, change directory to tp5

Use this command to run your application:

mvn spring-boot:run
CTRL + C to stop

After launching the Spring Boot application, it will be deployed to something like:

https://user-<sspcloud_username>-<6digits_number>-user<optional: -5000>.user.lab.sspcloud.fr/

Warning

If you meet that error: Web server failed to start. Port 5000 was already in use.

ps -aux | grep java
kill processes (ask for help!)

Sometimes mvn clean could be usefull.

2 Exercice

You’ll be working on an application that manages registrations for running races.

Features already implemented:

List of all Athletes
Add an Athlete
Delete an Athlete

Caution

To make it easier to use, you’ll be using:

Thymeleaf to provide an interface
An embedded, in-memory H2 database

However, bear in mind that in modern applications, Java is not used for GUIs. For example, the standard stack at INSEE is:

database: PostgreSQL
backend: Java (API that exposes endpoints)
frontend: React JS (uses API data for display)

2.1 Project structure

If you expand all the folders, you’ll notice that there are a lot of files.

Let’s focus on a few key points:

src/main/java/fr/ensai/running/: the java classes of your Layered Spring Boot application
- Layers: controller, service, repository, model…
- Application.java: the Main class to run your application
src/main/resources/
- templates/: html pages
- application.yml: Spring Boot properties of your application
- data.sql: Used to create and pop your database
pom.xml: Maven config

To go further

/config: To setup your app (security…)
LoggerAspect.java: Used to log before and after each method call

2.2 For students in IT sections

Let’s use a PostgreSQL database insted of an embedded H2:

In the SPPCloud, create a service PostgreSQL
Modify file application.yml to connect to this database
- search on internet for the necessary configuration
Optional: create a service CloudBeaver if you want to execute queries
- If all goes well, CloudBeaver will automatically connect to your database
- Otherwise you need to create a new connection entering Host, Database, Username and Password

2.3 Workflow example

You want to display all Athletes
You click on button Athletes on the navigation bar
- This takes you to the /athlete endpoint (check the navbar.html file if necessary)
In the Controller, it match with method findAllAthletes()
- This method calls method findAll() from the service
  - This method calls method findAll() from the repository
    - But if you check class AthleteRepository.java, there is no method findAll()
    - In fact, it’s a native method of CrudRepository, so it is not necessary to implement it
    - This method retrieves all athletes from the database
- Once the data has been retrieved, the method returns the string ‘allAthletes’
- Which means that you will be redirected to the allAthletes.html page.
athlete

sequenceDiagram
    participant IHM
    participant AthleteController
    participant AthleteService
    participant CrudRepository

    IHM->>AthleteController: Request findAllAthletes()
    AthleteController->>AthleteService: Call findAll()
    AthleteService->>CrudRepository: Call findAll()
    CrudRepository->>CrudRepository: Execute findAll()
    CrudRepository-->>AthleteService: Return list of athletes
    AthleteService-->>AthleteController: Return list of athletes
    AthleteController-->>IHM: Return allAthletes

2.4 API Rest

Before playing with the GUI, you’re going to create a few endpoints for your API.

In file ApiRestController.java, add the following endpoints:

GET an Athlete by id
DELETE an Athlete by id
CREATE an Athlete

If you haven’t any http client installed (Insomnia, Bruno, Postman…) on your machine you can use these bash commands to test your endpoints:

curl -X POST https://<your_url>.user.lab.sspcloud.fr/api/athlete \
     -H "Content-Type: application/json" \
     -d '{
           "firstName": "Floria",
           "lastName": "Guei",
           "age": 34,
           "gender": "Female"
         }'

curl -X DELETE https://<your_url>.user.lab.sspcloud.fr/api/athlete/1

Caution

The ApiRestController class is annotated with @RestController, and is therefore used to create endpoints for a REST API.

Next, we’re going to use simple Controllers to interact with the GUI.

If you prefer, you can continue to develop REST API endpoints without using the GUI.

Commit and push your code

2.5 Create competitions

Note

The goal is to display all competitions.

In your database there is a table called competition (loaded at start-up via the data.sql file).

CREATE TABLE competition (
    id_competition SERIAL PRIMARY KEY,
    designation    VARCHAR(255),
    city           VARCHAR(255),
    event_date     DATE,
    distance       FLOAT,
    max_athletes   INTEGER
);

Create a Model class for competitions
- To store dates, use LocalDate from java.time.LocalDate

Naming conventions

Please respect the naming conventions inherent in the languages (Java: camelCase, SQL: snake_case).

Create an interface CompetitionRepository to access the data in the database
Write a service class for competitions with methods allowing you to:
- list all competitions
- find a competition from its id
- delete a competition
Code a controller to handle these endpoints:
- /competition: display all competitions (allCompetitions.html)
  - In the Model, add an attribute named “competitions”
- /competition/delete/{id}: to delete a competition using its id

2.6 Binding Athletes and Competitions

We have Athletes.

We have competitions.

Now we want to register athletes for competitions.

Paste those queries at the end of data.sql

To be pasted at the end of data.sql

----------------------------------------------
-- Registration
----------------------------------------------

DROP TABLE IF EXISTS registration;

CREATE TABLE registration (
    id_registration       SERIAL PRIMARY KEY,
    id_athlete            BIGINT REFERENCES athlete(id_athlete),
    id_competition        BIGINT REFERENCES competition(id_competition),
    registration_date     DATE
);

INSERT INTO registration (id_registration, id_athlete, id_competition, registration_date) VALUES
(77770, 99990, 88880, '2024-03-01'),
(77771, 99991, 88881, '2024-03-02'),
(77772, 99992, 88882, '2024-03-03'),
(77773, 99993, 88883, '2024-03-04'),
(77774, 99994, 88884, '2024-03-05'),
(77775, 99995, 88880, '2024-03-06'),
(77776, 99996, 88881, '2024-03-07'),
(77777, 99997, 88882, '2024-03-08'),
(77778, 99998, 88883, '2024-03-09'),
(77779, 99999, 88884, '2024-03-10'),
(77780, 99990, 88881, '2024-03-11'),
(77781, 99991, 88882, '2024-03-12'),
(77782, 99992, 88883, '2024-03-13'),
(77783, 99993, 88884, '2024-03-14'),
(77784, 99994, 88880, '2024-03-15'),
(77785, 99995, 88882, '2024-03-16'),
(77786, 99996, 88883, '2024-03-17'),
(77787, 99997, 88884, '2024-03-18'),
(77788, 99998, 88880, '2024-03-19'),
(77789, 99999, 88881, '2024-03-20'),
(77790, 99990, 88882, '2024-03-21'),
(77791, 99991, 88883, '2024-03-22'),
(77792, 99992, 88884, '2024-03-23'),
(77793, 99993, 88880, '2024-03-24'),
(77794, 99994, 88881, '2024-03-25'),
(77795, 99995, 88883, '2024-03-26'),
(77796, 99996, 88884, '2024-03-27'),
(77797, 99997, 88880, '2024-03-28'),
(77798, 99998, 88881, '2024-03-29'),
(77799, 99999, 88882, '2024-03-30');

Code Model class Registration
Create Repository interface
Include a method to find a Registration from an Athlete and a Competition

Tip

You can use Query creation from method names

Add a method findAthleteIdByCompetitionId(Long idCompetition) using the custom query below

SELECT r.athlete.id
  FROM Registration r
 WHERE r.competition.id = :idCompetition

Now let’s add some methods in CompetitionService:

Add a method findRegisteredAthletes(Long idCompetition) returning the list of athletes registered for a given competition
Create a method deleteRegistration(Long idCompetition, Long idAthlete)

Try to delete a Competition. What’s wrong?

Update method CompetitionService.deleteById()
- to allow you to force deletion
Bonus: you will meet the same issue if you try to delete an Athlete. Fix it

2.7 Register an Athlete

Difficulty : ⭐ ⭐ ⭐

On the screen listing the athletes in a competition:

Add a drop-down menu listing Athletes no registered in the current Competition
Insert a button to register the selected Athlete

In Java classes:

Create a controller method registerAthleteCompetition(Long competitionId, Long athleteId)
Create a service method
- to create the Registration
- call the suitable repository method

If that was too easy, have fun creating other features.