Topic Name

Subtopic Name

Learning Outcome(Slide2)

6

Basics of branding and messaging

5

Target audience and segmentation

4

Different marketing channels

3

Creating value for customers

2

Understanding customer needs

1

What marketing means ?

Choose cool, soft colors instead of vibrant colors
Max 6 Points for Summary & Min 4

Topic Name-Recall(Slide3)

Hook/Story/Analogy(Slide 4)

Transition from Analogy to Technical Concept(Slide 5)

What is Relationship Mapping?

Relationship Mapping in Spring Boot (using JPA/Hibernate) defines how entities (Java classes) are connected to each other in the database.

Why Do We Need It?

Represents real-world data relationships clearly

Avoids data duplication in database tables

Enables easy data retrieval using object references

Maintains data consistency and integrity automatically

Example

Teacher  teaches  Student

"teaches" is the relationship between entities

One-to-One Relationship

Such a relationship exists when each record of one table is related to only one record of the other table.

For example, If there are two entities ‘Person’ (Id, Name, Age, Address)and ‘Passport’(Passport_id, Passport_no). So, each person can have only one passport and each passport belongs to only one person.

One-to-Many or Many-to-One Relationship

Such a relationship exists when each record of one table can be related to one or more than one record of the other table.

For example, If there are two entity type ‘Customer’ and ‘Account’ then each ‘Customer’ can have more than one ‘Account’ but each ‘Account’ is held by only one ‘Customer’.

Many-to-Many Relationship

This relationship exists when each record in the first table relates to multiple records in the second table, and vice versa.

For example, If there are two entity type ‘Customer’ and ‘Product’ then each customer can buy more than one product and a product can be bought by many different customers.

Major Relationship Annotations

 @OneToOne

One entity is related to only one other entity

@OneToMany

One entity is related to multiple entities

 @ManyToOne

Many entities are related to one entity

@ManyToMany

Many entities are related to many entities

Major Relationship Annotations

Defines a separate table that links two entities using foreign keys

@JoinTable

Defines the foreign key column that connects two related tables

@JoinColumn

Important Attributes

Points to primary key of another table

referencedColumnName

Defines foreign key in join table

joinColumns

Defines the non-owning side of relationship

mappedBy

Example : 


import jakarta.persistence.*;
import java.util.List;

@Entity
public class User {

    @Id
    @GeneratedValue
    private Long id;
    private String name;

    @OneToMany(mappedBy = "user")
    private List<Order> orders;
}

import jakarta.persistence.*;
import java.util.Set;
@Entity
public class Order{
@Id
@GeneratedValue
private Long id;
@ManyToOne
@JoinColumn(name="user_id")
private User user;
@ManyToMany
@JoinTable(name="order_product",
joinColumns=@JoinColumn(name="order_id"),
inverseJoinColumns=@JoinColumn(name="product_id"))
private Set<Product> products;
}

User.java

Order.java

Example : 


import jakarta.persistence.*;
import java.util.Set;

@Entity
public class Product {

    @Id
    @GeneratedValue
    private Long id;
    private String name;

    // Many products can belong to many orders
    @ManyToMany(mappedBy = "products")
    private Set<Order> orders;
}

Product.java

Understanding Unidirectional relationship

A unidirectional relationship is a relationship where only one entity knows or references the other entity.

Simple Example

Order

Customer

Get User from Order

Possible

Get Orders from User

Not Possible

Understanding Bidirectional relationship

Simple Example

Order

Customer

Get User from Order

Possible

Get Orders from User

Possible

A bidirectional relationship is when both entities know each other and can access data in both directions.

Fetch Strategies in JPA

Fetch is a strategy that defines when related (associated) data is loaded from the database.

It decides whether data is loaded immediately or only when needed

EAGER Fetch

LAZY Fetch

Loads data only when needed

Loads related data immediately

@ManyToMany(fetch = FetchType.EAGER)
private Set<Product> products;

@ManyToMany(fetch = FetchType.LAZY)

private Set<Product> products;

  • When you fetch an Order

  • Products are also loaded immediately

  • Products are NOT loaded immediately
  • They load only when accessed

Cascade Operations in JPA

Cascade is a feature that automatically applies operations from a parent entity to its related child entities.

When you perform action on parent, same action applies to child

Applies all operations (persist, remove, merge, etc.)

 CascadeType.ALL

CascadeType.PERSIST

Saves parent + child together

CascadeType.REMOVE

Deletes child when parent is deleted

CascadeType.MERGE

Updates child when parent is updated

Common Cascade Types

Introduction to Query Methods

In Spring Data JPA, query methods are abstract methods declared in a repository interface used to retrieve or modify data in a database

Query Methods

Spring Data JPA automatically generates the underlying query implementation at runtime based on the method signature, eliminating the need to write boilerplate code

Derived query method

Custom query method

Derived Query Methods

Derived query methods are query methods where the query is derived from the method name itself.

Here,

  • Method name = Query logic

  • Spring parses method name and builds query 


import org.springframework.data.jpa.repository.JpaRepository;
import java.util.List;
public interface UserRepository extends JpaRepository<User, Long> {
    List<User> findByName(String name);
    List<User> findByAgeGreaterThan(int age);
    List<User> findByNameAndAge(String name, int age);
}

Example

Structure of Derived Query Methods

Query Prefix

Your method name must start with one of these keywords, defining the primary action:

  • findBy
  • readBy
  • getBy
  • countBy
  • existsBy
  • deleteBy

Example: findBy

Property Expressions

After the prefix, chain the names of your entity's properties you want to query by.
Each property name should start with an uppercase letter.

Example: findByUsername

Condition Keywords

Refine your queries by adding logical operators or comparison keywords between properties. These allow for complex conditions.

  • And, Or
  • Between, LessThan, GreaterThan
  • Like, Containing, In
  • ...and many more!

Example: findByUsernameAndEmail
Like

Custom Query Method

A custom query method is a repository method where the query is written manually using the @Query annotation.


import org.springframework.data.jpa.repository.*;
import org.springframework.data.repository.query.Param;
import java.util.List;
public interface UserRepository extends JpaRepository<User, Long> {
    @Query("SELECT u FROM User u WHERE u.age > :age")
    List<User> getUsersAboveAge(@Param("age") int age);
}

Example:

When to Use

  • Complex queries

  • Joins between entities

  • Aggregations (COUNT, SUM)

  • When method names become too long

Simple Meaning

Instead of relying on method names,
we write our own query (JPQL or SQL)

Custom Query Method 


import org.springframework.data.jpa.repository.*;
import org.springframework.data.repository.query.Param;
import java.util.List;
public interface UserRepository extends JpaRepository<User, Long> {
    @Query("SELECT u FROM User u WHERE u.age > :age")
    List<User> getUsersAboveAge(@Param("age") int age);
}

Used to manually write the query that should be executed by Spring Data JPA.

:age is a named parameter placeholder inside the query.

@Param is used to bind the method parameter to the named parameter in the query.

Common Query Keywords

And / Or

Combine multiple conditions

findByNameAndAge(String name, int age);

Core Concepts (Slide 7)

Core Concepts (.....Slide N-3)

Summary

5

Build strong branding

4

Use different marketing channels

3

Target the right audience

2

Create and communicate value

1

Understand customer needs

Choose cool, soft colors instead of vibrant colors
Max 5 Points for Summary & Min 2

Quiz

Which platform is mainly used for professional networking and B2B marketing ?

A. Facebook

B. Instagram

C. LinkedIn

D. Snapchat

Quiz-Answer

Which platform is mainly used for professional networking and B2B marketing ?

A. Facebook

B. Instagram

C. LinkedIn

D. Snapchat

SpringBoot - Entity Relationships & Advanced JPA Features

By Content ITV

SpringBoot - Entity Relationships & Advanced JPA Features

  • 29

More from Content ITV