notes session 4 - JPA entities

unit2_building_spring_boot_webapp.md

@@ -46,7 +46,96 @@ From the currated dependancies you can omit the version when you add them to you
 Session 3 - 28/10/2022 - ended here
 
 <hr>
+## Github Workflow
 
+[Starts from here](https://sparkers.udemy.com/course/spring-framework-5-beginner-to-guru/learn/lecture/17789252#overview) Github workflow.
 
+- starting source
+- end source
 
-***Session 4 - 30/10/2022 : [Starts from here](https://sparkers.udemy.com/course/spring-framework-5-beginner-to-guru/learn/lecture/17789252#overview) Github workflow.***
+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
+
+```java
+@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
+
+<hr>
+
+
+
+***Session 5 - 31/10/2022 : [Starts from here](https://sparkers.udemy.com/course/spring-framework-5-beginner-to-guru/learn/lecture/17792132#notes) Equality in hibernate***