Spring Data JPA Relationships - ManyToMany, ManyToOne & OneToMany

[@BoualiAli]

Join the Micro Services course waiting list and get and get an exclusive *EARLY-BIRD discount* aliboucoding.ck.page/d0f9317e13

[@DiplomasizKodcu]

How did I not seeing your videos before? Did you know your the only one who explained entire stuff? I will watch your entire list and share your account for those who need. Thanks a lot for great content.

[@BoualiAli]

Glad you liked it!

[@santhosha-z5x]

thank you so much you saved my interview time by minimizing all extra's i recommend this videos to others who didn't understand relationships properly.

[@landry_john]

Thank you for that great lesson about Spring Data JPA Relationships.

[@BoualiAli]

Glad it was helpful!

[@taiwoobadare]

Very very good explanation, well simplified, great job!

[@BoualiAli]

Glad you enjoyed it!

[@GuilhermeMirandaZelinschideArr]

the only video that made me understand the concept great work

[@BoualiAli]

glad to hear that!

[@hazel-BKJ]

Your video is beyond reproach, from theoretical concepts to practical application. Thank you very much for the content, Mr Ali, which is full of pedagogy and enables me to make progress as a beginner with the spring boot framework.

[@BoualiAli]

You are most welcome

[@ines_edim]

1. You have good well drawn out diagrams and visualizations, it's very helpful 2. Your explanations shows that you have solid fundamentals [Coding + SQL] 3. You gave Practical and Relatable examples. 4. Kudos to you. I am coming from a C++ background, and I appreciate the attention to details in this video. I'll be sure to watch the playlist. You've got 1 new subscriber here.

[@BoualiAli]

Great and detailed feedback. Happy you liked it!

[@shenanvindinu]

Much love ❤❤

[@natanduarte5273]

UR AN LEGEND i sspent more than 4 hors trying to get this right, and the u showed up THX

[@ShermukhammadKarimov]

thanks for this amazing tutorial

[@parmodprajapati]

Hi Great, Could you please make videos on Spring Security like this one.?

[@BoualiAli]

Already did. Check the videos

[@sithumsathsara7966]

Good😀

[@khaledoueslati66]

Very Nice video keep the great work up 🙌🙌

[@BoualiAli]

Thank you so much 😁

[@kishorem5101]

Why I got sleepy when I'm heard your voice 💤😴😴

[@okeowoaderemi]

Amazing Tutorial I just joined your discord

[@BoualiAli]

Awesome thank you!

[@satyamsc]

Nice.. Easy to understand. !!!.

[@BoualiAli]

Happy to know your feedback 😁

[@wantedlepota9960]

I would have loved to see how you test this, how would the JSON input would look like representing those entity relationships

[@markotomic4368]

Thank you Ali for this wonderfull explanation!

[@BoualiAli]

You are very welcome

[@mohamedhediaissi598]

Thank you so much for this video !! It really helped me a lot !!

[@mamadoumorobah1777]

Merci beaucoup pour le partage de savoir

[@BoualiAli]

My pleasure Don’t forget to share the video 😄

[@genusleemapedze1177]

Would be glad if you can create maybe a single end to end application with spring security included in the app and also learning more about the DTOs e.g a blog app with several roless

[@BoualiAli]

I will consider this idea.

[@solowolf5304]

@@BoualiAli yes plz do consider this

[@inihood]

@@BoualiAli Please do it

[@BoualiAli]

@@inihood i already published a spring security video

[@Ramziddin_Rustamov]

27:15 visualization:) never mind

[@sphesihlemanuel2933]

Great video, this was very helpful

[@BoualiAli]

Glad it was helpful!

[@messironaldo1708]

That was soo helpful. Thank you!

[@BoualiAli]

My pleasure

[@Supremevillacom-house]

🎉🎉 thanks 👍👍😊

[@BoualiAli]

Welcome 😊

[@trinhlong2665]

Thank you Bouali Ali. Would be glad if you can complete this project by creating some Rest Controller class. I hope to see you have more videos about this course.

[@BoualiAli]

I already have videos about that. Check the playlist Spring workshops

[@abhinavjain8613]

Please add link

[@aboubacardiaby3700]

Salut Mr Bouali j'ai une question pertinante pour vous. le faite de créer une liste lorsqu'on a une annotation @OneToMany dans une classe permet de faire quoi concrètement

[@marouenghozzi4778]

How can we decide who’s the owner of the relationship between two entities ?

[@mursalin3698]

well done

[@BoualiAli]

Thanks

[@supun_sandaruwan]

awesome video 🔥 Thank you

[@BoualiAli]

Glad you liked it!

[@amenimensi8817]

good job

[@BoualiAli]

Thanks

[@mohamedoueslati462]

Good job , Thanks Ali :)

[@BoualiAli]

Always welcome

[@AshishRohillax]

Thanks a lot, really helpful

[@BoualiAli]

Happy to know that 🔥

[@apexyu164]

in all this relationship, which one will auto ipdate the table if one insert happen

[@elliotsaii7904]

that's was awesome video

[@BoualiAli]

Thank youu

[@nourhenjridi7963]

SVP comment vous affichez le diagramme de classe représentant les entités dans votre projet Spring Boot avec une base de données ?

[@kushagraahire1871]

thanks

[@solowolf5304]

New viewer here. I hope 10K subscribers would be a good motivation for you to bring more good content like this !!

[@BoualiAli]

Absolutely

[@ernanibatista1806]

Tks but when we insert in the table employee , adress_id retuning null

[@mohamedwiem4965]

Amazing content as well, just I wanna ask if the integration of database and diagrams you use exists in STS or intellij community edition or just in intellij ultimate !

[@BoualiAli]

Happy you liked it. Not sure about sts, but for Intellij it is just ultimate version

[@angsh]

Gold!

[@BoualiAli]

Thank you

[@samirbenaziz520]

salem khouya ya3tik sa7a 3al vidéo juste question : OneToMany wel ManyToOne dima relation binéthom unidirectionnelle ???

[@AntonioCabralNumberOne]

Thank you once again for your dedication with your beautifully explained videos! I have one question about ManyToMany relationships: If you need an extra column in the relationship table between (in your case) the Employee and the Mission tables, let's say e.g. a "created_at" column, how would you add it, set it and get it? Thank you in advance!

[@RandomSrr751]

Hi there! So, I'm about a month late, and I'm also just getting started with coding, but I solved this situation last week. In ManyToMany relationships, the intermediate table is generated automatically, which means you can't easily add more attributes without modifying the relationship itself. The only way I found to resolve this involves actually not using ManyToMany but setting up two OneToMany relationships between employees/missions on the "One" side, linking them to a third entity that contains both IDs along with any extra attributes. Using an example, this would be represented by the EmployeeMission class, which includes employeeId, missionId, and createdAt attributes. As Ali shows here, for OneToMany relationships, it's important to specify the "mappedBy" annotation, and I also found it helpful to specify the fetch type. I hope my explanation is clear and helpful. Have a great day!

[@parmodprajapati]

Hi, When we go for Unidirectional mapping and which is best according to requirement? We can also set the employee id to the address table so why should we address id set to the employee table.

[@BoualiAli]

It depends on the logic and needs for your application

[@fernandoereno5597]

Thank you!!!

[@BoualiAli]

My pleasure

[@wassimsakri8654]

thank you

[@BoualiAli]

My pleasure

[@MFM88832]

Good video but it would be more informative if you showed Crow's foot notation in your visaulisation diagram.

[@BoualiAli]

Ok next time

[@chokribenrejeb8115]

Thank you,. how we can achieve ManyToMany relationship whene the join Table should have some data.

[@BoualiAli]

You need to create an extra entity that will hold the relation and the extra fields as well

[@kamilleskamilless8113]

@@BoualiAli could you please create video about that?

[@BoualiAli]

@@kamilleskamilless8113 about what exaclty?

[@emonadriane5525]

Thanks really @Bouli ..can you please make a video/tutorial on making an e-commerce API including uploading product image plus attaching the different prices. Or maybe a destinations API

[@BoualiAli]

I really would like to, bit this gonna take so much time. I hope I can do it one day

[@emonadriane5525]

​@@BoualiAli Really thanks. Stay blessed!

[@mohamedwiem4965]

thank u ! employee_mission was automatically generated in our database , should we create employee_mission class in our entity package or is not necessary ?

[@BoualiAli]

if you don't have any extra fields, you don't need to

[@apexyu164]

How to add database to spring in right panel?

[@dorrakadri1474]

can u explain the cascade types

[@BoualiAli]

Will note that for the next video

[@adelteyeb2427]

Thinks can you make a video about MVC architecture

[@BoualiAli]

Happy you liked it! Soon

[@mugenzideodate5733]

Can you help us, full project by using spring boot multipe tables like 3 tables from database on back end and fetch data to front-end in single table?

[@BoualiAli]

aliboucoding.com/courses

[@zqgAFf]

Thank you so much for such a nice clean video , However I made the simlar entities with one to one bidirectional , when I check the database , it does have each other id as foriein key ,however my app won't start again , but if add something like mapped by employee and add cascade = cascadeType.All , then there won't be two foreign key , there is only one address_id ,but the other foreign key won't appear from the other table ....I am confused

[@BoualiAli]

Why your app is not starting after adding one to one? Can you provide some logs in the discord server (screenshots) to make easier to understand

[@zqgAFf]

@@BoualiAli Yeah I noticed on one to one bidirectional it is better not to provide mapped by on one entity otherwise,otherwise there’s only one foreign key like unidirectional

[@bagzhansadvakassov1093]

You haven't left the source code?

[@thanhninh8677]

Can you give me the link of the next video , i can't find it

[@BoualiAli]

Spring Data JPA | Hibernate kzbin.info/aero/PL41m5U3u3wwkS8BU0fIeRQwY3hK4VlFlX

[@haobui8913]

Can anyone tell me what is the function of MappedBy????

[@fumano2679]

I have a problem when inserting an entry with the many-to-one relationship. Lets say i have created a department with the id of 1 in my database and now want to create a employee. I a few cases to do this. 1. By placing the department_id = 1 int the json, 2. by placing the department = 1 in the json, 3. by placing the department equal to the department json from my db entry, 4. by getting the department object from an api call and then employee.setDepartment(department). None worked. Is it not possible to create an Employee by referencing the department id?

[@BoualiAli]

when creating an employee you need to set the department object and pass the department is Here is an example Department dep = new Department() dep.setId(departmentId) // the one you get in your request / object / param (depends how you get it) Employee emp = new Employee() emp.setField() emp.set....() emp.setDepartment(dep) repository.save(emp)

[@kevinameda2711]

Hi @Bouli for the great tutorials. Could you please make a video about spring security with oauth will appreciate thank you in advance

[@BoualiAli]

Already have one about spring security. Check it in the same playlist

[@kevinameda2711]

@@BoualiAli I did and it is an absolute honour to even talk to you. Where can I reach u out to talk further?

[@BoualiAli]

@@kevinameda2711 the honor is mine You can reach me on our discord server

[@amineessaoud1493]

Does OneToMany & OneToMany exist in Spring Boot ?

[@BoualiAli]

yes

[@Sumeshkumarback]

Perform CRUD operation in above relationship

[@orestdymarchuk2910]

When you create an Entity, you created an Integer field with the "id" annotation. Can you please clarify why this field should be an Object type and not a primitive one?

[@BoualiAli]

Object by default is null Premitive like int by default 0 You null on the id to help hibernate well manage the entities. Checkout my new course about spring data jpa and you will understand all this details and master this topic aliboucoding.com/courses

[@sureshattimarad1796]

Bacause we use ArrayList type field to hold MANY objects, Since ArrayList implements List interface that SUPPORTS only OBJECT TYPE not the primitive type

[@jopadjr]

46th...Thanks

[@BoualiAli]

Welcome

[@osasereuhunmwangho5293]

Thank you Bouali Ali. This is very concise and really gainful for me. For the one-to-one relationship, in what context is the relationship uni-directional or bi-directional?. Thank You

[@BoualiAli]

Unidirectional Relationship: This means that one entity has knowledge of the other, but not vice versa. In other words, if you have two entities, say EntityA and EntityB, and if EntityA has a reference to EntityB (but EntityB does not have a reference to EntityA), then it's a unidirectional relationship. Unidirectional relationships are simpler and less complex, and are suitable when there is no need for the referenced entity (EntityB in our example) to know about the entity that is referencing it (EntityA). For instance, if you have a User entity and a Profile entity, and each User has one Profile, but a Profile does not need to know which User it belongs to, you can model this as a unidirectional relationship from User to Profile. Bidirectional Relationship: This is when both entities are aware of each other - EntityA has a reference to EntityB, and EntityB also has a reference to EntityA. This kind of relationship is a bit more complex due to the need to keep both sides of the relationship in sync. Bidirectional relationships can be useful when there is a need for both entities to be aware of each other. For example, if you have a Customer entity and a BankAccount entity, and each Customer has one BankAccount, but a BankAccount also needs to know which Customer it belongs to, then you would model this as a bidirectional relationship.

[@plowman5260]

Thank you for your help

[@BoualiAli]

Thank you too!

[@arslanoulhaci9965]

VIZU ALI ZATION visualization

[@Razes9ooo474lO4]

employee and department uni directional or bi-directional , department table doesnt have any fk of employee

[@moriahnjsahkhar8764]

How do i handle circular reference error in onetomany and manytoone.. ive tried @jsonmanaged and @jsonbackreference .. it kinda works but not fully.. i still get the stackoverflow error in the frontend which is thymleaf and also when i use toString method

[@stevegatspaul]

Hey, Amazing content as always, but I have a question about how to use this in "@Repository public interface EmployeeDao extends JpaRepository", for example : findByEmployeeId and get: Employee Info and his address and his Mission and his Department.

[@BoualiAli]

Hi, can explain your question? I didn’t understand

[@stevegatspaul]

@@BoualiAli how to use join query in spring data jpa, use Employee_Id and get: Employee Info and his address and his Mission and his Department. thank you in advance for your reply. 😀

[@imedhr1814]

thanks but you did not explain the difference between unidirectional and bidirectional in @OneToMany @ManyToOne !!

[@BoualiAli]

It was already explained in the beginning of the video

[@KlanBr1]

i am doing this tutorial with pgAdmin 4, and the relation ONETOONE, it's looks like ONETOMANY on my DER

[@BoualiAli]

How is that possible? Can you share some screeshots and code snippets on the discord server?

[@miloudseo7883]

Je crois au niveau entity employee tu doid crée comme ceci:@ManyToOne(mapping="employee") Private collection departmant;

[@BoualiAli]

Pourquoi?

[@miloudseo7883]

@@BoualiAli suivant la cardinalite que vous mentionné dans votre diagramme de class.

[@BoualiAli]

@@miloudseo7883 peux tu expliquer plus?

[@miloudseo7883]

@@BoualiAli clé étranger de la table employee doit etre dans la table départemant car un employee appartient à plusieurs départemant, et chaque départemant ayant une seul employee(ma raisonnement suivant la cardinalité que vous avez mentionné, en uml en raisonne comme ca)

[@miloudseo7883]

@@BoualiAli je crois tu dois changer la cardinalité entre table employee(*) et departemant(*) to ManyToMany