Spring Boot Lesson

Quick Start

To run the project:

Step 1: CD to the project root directory cart_api

Step 2: Run ./mvnw spring-boot:run command

Lesson Overview (9 Mar 2023, Fri)

Lesson Coverage:

1. Move complex logics in /carts to a @Service class
2. Adding User entity
3. Use of UserID header as a mock authentication header

Firebase SDK has a major shift and no longer support signInWithEmailAndPassword from the backend Firebase Admin SDK using Java.

1. Move complex logics to @Service class

Refer to the add and decrement methods in CartService.java where complex logics is moved into.

Refer to CartController.java where the code mainly focuses on handling http request and response (status).

A custom exception called NotFoundException.java is created to help us identify scenario where the productId is not found.

2. Adding the User Entity

Let's refer to our ERD again while creating our User Entity class.

The SQL Statements required to generate the user table:

create table user (
    id int not null auto_increment,
    email varchar(255) not null,
    created_at timestamp not null default current_timestamp,
    primary key (id)
);

alter table cart add column user_id int;
alter table cart add constraint fk_cart_user foreign key (user_id) references user(id);

If you need to check all foreign keys in the DB, use the following command:

SELECT TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME, REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE REFERENCED_TABLE_SCHEMA = 'cartdb';

3. Using @RequestHeader to capture value from HTTP Header

public ResponseEntity<List<Cart>> findAll(@RequestHeader("user-id") int userId)

See CartController.java for full details.

We should also implement this for every methods in CartController.java. This will eventually affect CartService.java as well. All request to /carts must contains a user-id header.

End