Spring Boot One-To-One Mapping Demo With H2 database

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("[e-mail]");
        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