The previous Spring Boot + Spring data JPA will be reused, modify to support PostgreSQL database.

Technologies used :

• Spring Boot 2.1.2.RELEASE
• Spring 5.1.4.RELEASE
• Hibernate 5.3.7
• HikariCP 3.2.0
• PostgreSQL driver 42.2.5
• Maven 3
• Java 8

Puts a postgresql driver and defined the data source url in application.properties. Done, Spring Boot is able to connect to a PostgreSQL database.

	<dependency>
		<groupId>org.postgresql</groupId>
		<artifactId>postgresql</artifactId>
	</dependency>

1. Maven

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
		 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <artifactId>spring-boot-data-jpa</artifactId>
    <packaging>jar</packaging>
    <name>Spring Boot Spring Data JPA</name>
    <version>1.0</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.2.RELEASE</version>
    </parent>
    <properties>
        <java.version>1.8</java.version>
        <downloadSources>true</downloadSources>
        <downloadJavadocs>true</downloadJavadocs>
    </properties>
    <dependencies>
        <!-- jpa, crud repository -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <!-- PostgreSQL -->
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.22.0</version>
            </plugin>
        </plugins>
    </build>
</project>

2. Configure PostgreSQL

2.1 Update the PostgreSQL settings in spring.datasource.*

## default connection pool
spring.datasource.hikari.connectionTimeout=20000
spring.datasource.hikari.maximumPoolSize=5
## PostgreSQL
spring.datasource.url=jdbc:postgresql://localhost:5432/postgres
spring.datasource.username=postgres
spring.datasource.password=password
#drop n create table again, good for testing, comment this in production
spring.jpa.hibernate.ddl-auto=create

Done.