Walkthrough: Cars Demo - Spring Data, JPA, Hibernate

In this walkthrough, we revisit the Car Integration Tests that we worked on in yesterday’s walkthrough Walkthrough: Spring Integration Tests. We’ll refactor the app to use Postgres and Hibernate.


  1. In the terminal go to project folder for Car Integration Tests
  2. Checkout the branch that contains the solution for the Day 3 walkthrough. Example: $ git checkout master or $ git checkout solution
  3. Create a new branch for today’s work: $ git checkout -b day4-add-hibernate

Our Tasks

Each section outlines one task or group of tasks we need to complete.

Set Up A Postgres DB

  1. From psql, create a Postgres user: psql=# create user car_user with encrypted password 'catdogbluehouse';
  2. Create a database: psql=# create database car;
  3. Grant the user access to the database:psql=# grant all privileges on database car to car_user

Configure the App to use the Database

To configure our Spring application to run with Postgres we will need to:
  • Update our gradle dependencies
  • Configure our database configurations in application.properties
  • Mark our models with the @Entity annotation
  • Create new interfaces that extend JpaRepository

Check out the Configuration: Spring & Postgres to learn how to configure our Spring app to work with Postgres.

We also will be working with sensitive information, and it would be a good idea to read Configuration: Environment Variables - IntelliJ.

In that article we:
  • Created an application.properties file
  • Added configurations about our database to the file
  • Used environment variable tokens to keep our database information secure
  • Added environment variables to our runtime configuration


Committing passwords to source control is a BAD idea. We are using a spring data feature that searches for and uses enviroment variables. Read more about Spring Boot/Data configuration.

Add Annotations to Car Model

package org.launchcode.training.models;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

public class Car {

    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private int id;
    //rest of class is not shown...

Add CarRepository

package org.launchcode.training.data;

import org.launchcode.training.models.Car;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

public interface CarRepository extends JpaRepository<Car, Integer> {

Autowire Repositories into Controllers

public class CarController {

    private org.launchcode.training.data.CarRepository carRepository;

Autowire Repositories in Tests

public class CarControllerTests {

    private MockMvc mockMvc;

    private CarRepository carRepository;

Configure Test DB

Add a /car-integration-tests/src/test/resources/application-test.properties file with below contents.

spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.H2Dialect

We need to make sure our test properaties are used when running tests. Add the below code to /car-integration-tests/src/test/java/org/launchcode/training/IntegrationTestConfig.java. The @Transactional annotation insures that any sql executed during a test will only exist for that single test and won’t pollute another test.

@TestPropertySource(locations = "classpath:application-test.properties")

Do the Tests Pass?

If not, fix them ;p