My notes during the lecture of Udemy : https://sparkers.udemy.com/course/spring-framework-5-beginner-to-guru

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Spring 5 course : Udemy - Unit 2

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Unit 2: Building a Spring Boot Web App

Quick overview of Spring in a very productive way.

Generate html with dynamic content.

Disclaimer: how to use this but not going fully in details in this chapter.

Spring Boot
Spring MVC
Spring Data JPA (Hibernate)
H2 database

Spring Initializr

Back in time you needed to create you own project with maven. Spring Initializr does this job for you (maven or gradle).

https://github.com/spring-projects/spring-boot/tree/main/spring-boot-project/spring-boot-starters

Create a simple webapp with: https://start.spring.io/

Spring Web (Spring mvc)
Spring Data JPA (abstraction for hibernate)
H2 Database (our in memory database)

Open the project in IntelliJ

For a maven project: From Existing source > Select the pom.xml file at the root of the project

Look at currated dependencies in the pom.xml by ctrl+click on the parent.artifactId

From the currated dependancies you can omit the version when you add them to your pom.xml because they are references in spring-boot-parent-2.x.x.RELEASE.pom

Session 3 - 28/10/2022 - ended here

Github Workflow

Starts from here Github workflow.

starting source
end source

1- fork the project and clone the repo to local

2- co fork start with starting source

3- use compare feature of git with relevant branch

Compare to source (not fork)

1st- >Copy the cloning url from original project

git remote add sfgRepo <protocol:originalrepo/url>
git fetch sfgRepo

Then in the GUI: git > compare with branch.

JPA Entities

Java Persistance API - api for Hibernate.

Modeling the data.

Creating two POJOs

Book

title
isbn
authors (as Set<Author>)

Author

firstName
lastName
books (as Set<Book>)

NOTE: JPA requires a 0 args construcor

Tips: Bring up the menu with alt+insert for constructors, getters and setters

Now we are going to make them official JPA entities that can be persisted.

Leakage - object leaking up in an object database.

Assign JPA Id's

@Entity
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    ...

JPA Relationships

Many to many relationships. (there will be a dedicated section in the framework course).

@ManyToMany(mappedBy = 'authors')

@ManyToMany
@JoinTable(name= 'author_book', joinColumns = @JoinColumn(name= 'book_id'), inverseJoinColumns = @JoinColumn(name= 'author_id'))

Session 4 - 30/10/2022 : ended here

Equality in Hibernate

Starts from here Equality in hibernate

Leakage necessary - hibernates uses equals and hashcode methods.

Equals and HashCode

@Override the methods to have a logic around the id property.

Tips: use alt+insert equals() and hashCode() metods for the id field

ToString

Tips: alt+insert implement toString( )

Spring Data Repositories

Spring Data with JPA helps us implement repositories.

Prevents us to write all this "ceremonial code" that JDBC needs.

Create a new package repositories

For each domain object create an interface.

Example: AuthorRepository.java

public interface AuthorRepository extends CrudRepository<Author, Long> { }

Session 5 - 31/10/2022 : ended here

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