There are three basic entity relationships:-
- One-to-One
- One-to-Many/Many-to-one
- Many-to-Many
Installation
Clone project from here:- Click Here
Import Maven based project in any of your Favourite IDE.
./mvnw spring-boot:run
Output
Open in Browser
Access H2 Database.
http://localhost:8080/h2-console
Usage
MainClass.java
run() method is run when the application is started. The data is added in the database.
@Override
public void run(String... args) throws Exception {
Customer customer = new Customer();
customer.setName("Atharva Siddhabhatti");
customer.setEmail("atharvasiddhabhatti@gmail.com");
Item item = new Item();
item.setName("Macbook");
item.setQty(1);
customer.setItem(item);
item.setCustomer(customer);
customerRepository.save(customer);
Customer.java
Following annotations are used in the Customer Entity class to join two tables.Check the class file to view other entities.
@OneToOne(fetch =FetchType.LAZY, cascade = CascadeType.ALL)
@JoinColumn(name = "item_id")
private Item item;
Item.java
@OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "item")
private Customer customer;
Output
Configuration
application.properties
spring.jpa.show-sql = true
# Enabling H2 Console
spring.datasource.url=jdbc:h2:mem:testdb
spring.jpa.defer-datasource-initialization=true
spring.h2.console.enabled=true
# Enable Web Access
spring.h2.console.settings.web-allow-others=true
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