Setting Up the Database and Spring Data JPA

In the previous chapter, you learned about Spring Boot’s fundamentals to develop our backend application, such as dependency injection, beans, and annotations. In addition, we now know how to create a Spring Boot project using Spring Initializr.

This chapter will teach you how to connect your Spring Boot application to a database by adding a PSQL container and PostgreSQL dependencies and accessing data using the Java Persistence API (JPA).

In this chapter, we will cover the following topics:

• Connecting to database using a PSQL container
• Spring Data JPA
• Adding Spring Data JPA and PostgreSQL dependencies
• Connecting to a database

Technical requirements

Here is what you need to complete this chapter:

• PostgreSQL: https://www.postgresql.org/download/windows/
• pgAdmin: https://www.pgadmin.org/download/
• Docker: https://docs.docker.com/get-docker/

Connecting to a database using a PSQL container

This section will teach us how to set up and configure our PostgreSQL in our terminal by using the conventional method, using the installer, or through a Docker container. But first, let’s discuss what PostgreSQL is and what its advantages are.

PostgreSQL

PostgreSQL is an open source object-relational database system that uses the SQL language to store and handle complicated and large workloads. PostgreSQL also supports both SQL (relational) and JSON (non-relational) querying. It is commonly used as primary data storage for geospatial and analytics applications because of its flexibility and rich features. Its community has improved and continuously backed it for more than 20 years to add more features and reliability to the database system.

PostgreSQL’s flexibility means that it is widely used in developing applications. Here are some of the everyday use cases:

• Scientific data: Research projects can be...

Spring Data JPA

Spring Data JPA (Java Persistence API) is a widely used specification for managing relational data in Java applications. It helps develop Spring, as it reduces boilerplate code by not implementing read and write operations. It also handles the complex process involved in JDBC-based accessing of database and object-relational mappings.

Before discussing Spring Data JPA, let’s discuss its clear advantages and why it is commonly used in Spring development.

The advantages of Spring Data JPA

The following are the advantages of Spring Data JPA:

• No-code repositories: Spring Data JPA promotes no-code repositories, which means that we don’t have to write the repository pattern, which creates a lot of repetitive code. It provides a set of interfaces that we can use to extend our classes to apply data-specific implementations.

For example, we have a BlogRepository class in our application; when we extend it with the CrudRepository<Blog...

Adding Spring Data JPA and PostgreSQL dependencies

This section will add Spring Data JPA, PostgreSQL, and other valuable dependencies to our application. We will add the dependencies with Spring Initializr and an existing Spring Boot project.

Adding with Spring Initializr

Adding dependencies after creating a Spring Boot application using Spring Initializr is simple. We only need to select the dependencies on Initializr before generating our project:

1. The first thing to do is to go to https://start.spring.io/ or to your IntelliJ IDEA (for Ultimate users) to open Spring Initializr (for a recap of the Using Spring Initializr section, refer to Chapter 3, Moving into Spring Boot).
2. Choose your project if it will use Maven or Gradle and set the required configurations, which are Group, Artifact, Name, Description, Package name, Packaging, and the Java version of the project.
3. Next, click Add Dependencies at the top right and select the following dependencies:
   • Spring Data...

Connecting to a database

We have already configured our PostgreSQL database and initialized our Spring Boot application with the needed dependencies. Now, we will learn how to connect our PostgreSQL to our application. There are two ways we can connect to our database – the first is through Spring JDBC, and the other is Spring Data JPA. Spring Data JPA is the most convenient way to connect to our database, but we will demonstrate both methods in this section.

Configuring the database properties

The first thing we need to do is configure the database properties in our Spring Boot application. We need to specify the server URL of the database, the admin username, and the password by adding the following source code to the application.properties file:

spring.datasource.url=jdbc:postgresql://localhost:5432/springDB
spring.datasource.username=postgres
spring.datasource.password=password

In the preceding example, we can see that we have configured the basic connection...

Summary

That brings you to the end of this chapter. Let’s have a recap of the valuable things you have learned. You learned how to set up PostgreSQL on your local machine using the installer or Docker container.

You have also learned about the concepts and advantages of Spring Data JPA in Spring Boot and how to add it to your application, which is helpful in creating services with CRUD capabilities with less boilerplate code.

Last but not least, you learned how to connect your Spring Boot application with the PostgreSQL database using JDBC and Spring Data JPA.

In the next chapter, we will be learning how to start our server, how to add controllers, models, and services in our code, and about Redis for caching.