Spring Boot + Spring Data JPA + PostgreSQL Example

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In this tutorial, you’ll learn how to configure Spring Boot, and Spring Data JPA to support a PostgreSQL database.

Check out these two links to download and install a PostgreSQL database on your machine.

What we’ll build

We will build CRUD RESTFul APIs for a Simple Employee Management System using Spring Boot 3, JPA, and PostgreSQL database. 

Following are five REST APIs (Controller handler methods) created for the Employee resource.

Technologies and Tools Used

  • Spring Boot - 3+
  • JDK - 17 or later
  • Spring Framework - 6+
  • Hibernate - 6+
  • JPA
  • Maven - 3.2+
  • IDE - Eclipse or Spring Tool Suite (STS)
  • PostgreSQL 
  • Postman

Create Spring Boot Project

Use spring initializr to create a new Spring boot project with the name: springboot-postgresql-jpa-hibernate-crud-example

Maven Dependencies - pom.xml file

<?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>

	<groupId>net.guides.springboot2</groupId>
	<artifactId>springboot2-postgresql-jpa-hibernate-crud-example</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>springboot-postgresql-jpa-hibernate-crud-example</name>
	<description>springboot-postgresql-jpa-hibernate-crud-example</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.0.4</version>
		<relativePath /> <!-- lookup parent from reposictory -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>17</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-validation</artifactId>
		</dependency>
		<dependency>
			<groupId>org.postgresql</groupId>
			<artifactId>postgresql</artifactId>
			<scope>runtime</scope>
		</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>
		</plugins>
	</build>

</project>
Note that we are using Spring Boot 3 and Java 17.

Configure PostgreSQL Database

Let’s configure Spring Boot to use PostgreSQL as our data source. We are simply adding PostgreSQL database URL, username, and password in the src/main/resources/application.properties file - 
spring.datasource.url=jdbc:postgresql://localhost:5432/employees
spring.datasource.username=postgres
spring.datasource.password=root
spring.jpa.show-sql=true

## Hibernate Properties
# The SQL dialect makes Hibernate generate better SQL for the chosen database
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect

# Hibernate ddl auto (create, create-drop, validate, update)
spring.jpa.hibernate.ddl-auto = update

Create JPA Entity - Employee.java

Let's create an Employee JPA entity with the following content:
package net.javaguides.postgresql.model;

import jakarta.persistence.*;

@Entity
@Table(name = "employees")
public class Employee {

	private long id;
	private String firstName;
	private String lastName;
	private String emailId;
	
	public Employee() {
		
	}
	
	public Employee(String firstName, String lastName, String emailId) {
		this.firstName = firstName;
		this.lastName = lastName;
		this.emailId = emailId;
	}
	
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	
	@Column(name = "first_name", nullable = false)
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	
	@Column(name = "last_name", nullable = false)
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	
	@Column(name = "email_address", nullable = false)
	public String getEmailId() {
		return emailId;
	}
	public void setEmailId(String emailId) {
		this.emailId = emailId;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", emailId=" + emailId
				+ "]";
	}
}
@Entity: This annotation indicates that the class is a JPA entity and should be managed by the persistence context.

@Table: This annotation specifies the name of the table to which the entity is mapped.

@Id: This annotation indicates that the field is the primary key of the entity.

@GeneratedValue: This annotation specifies the strategy used for generating the primary key value.

@Column: This annotation specifies the mapping of the field to the corresponding column in the database.

Create Spring Data Repository - EmployeeRepository.java

Let's create an EmployeeRepository interface that extends the JpaRepository interface:
import net.javaguides.postgresql.model.Employee;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long>{

}

Create Spring Rest Controller - EmployeeController.java

Let's build CRUD REST APIs for the Employee resource.
package net.javaguides.postgresql.controller;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import jakarta.validation.Valid;

import net.javaguides.postgresql.exception.ResourceNotFoundException;
import net.javaguides.postgresql.model.Employee;
import net.javaguides.postgresql.repository.EmployeeRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api/v1")
public class EmployeeController {
	@Autowired
	private EmployeeRepository employeeRepository;

	@GetMapping("/employees")
	public List<Employee> getAllEmployees() {
		return employeeRepository.findAll();
	}

	@GetMapping("/employees/{id}")
	public ResponseEntity<Employee> getEmployeeById(@PathVariable(value = "id") Long employeeId)
			throws ResourceNotFoundException {
		Employee employee = employeeRepository.findById(employeeId)
				.orElseThrow(() -> new ResourceNotFoundException("Employee not found for this id :: " + employeeId));
		return ResponseEntity.ok().body(employee);
	}

	@PostMapping("/employees")
	public Employee createEmployee(@Valid @RequestBody Employee employee) {
		return employeeRepository.save(employee);
	}

	@PutMapping("/employees/{id}")
	public ResponseEntity<Employee> updateEmployee(@PathVariable(value = "id") Long employeeId,
			@Valid @RequestBody Employee employeeDetails) throws ResourceNotFoundException {
		Employee employee = employeeRepository.findById(employeeId)
				.orElseThrow(() -> new ResourceNotFoundException("Employee not found for this id :: " + employeeId));

		employee.setEmailId(employeeDetails.getEmailId());
		employee.setLastName(employeeDetails.getLastName());
		employee.setFirstName(employeeDetails.getFirstName());
		final Employee updatedEmployee = employeeRepository.save(employee);
		return ResponseEntity.ok(updatedEmployee);
	}

	@DeleteMapping("/employees/{id}")
	public Map<String, Boolean> deleteEmployee(@PathVariable(value = "id") Long employeeId)
			throws ResourceNotFoundException {
		Employee employee = employeeRepository.findById(employeeId)
				.orElseThrow(() -> new ResourceNotFoundException("Employee not found for this id :: " + employeeId));

		employeeRepository.delete(employee);
		Map<String, Boolean> response = new HashMap<>();
		response.put("deleted", Boolean.TRUE);
		return response;
	}
}

Exception(Error) Handling for RESTful Services

ResourceNotFoundException

Let's create a ResourceNotFoundException.java class with following content to it:
package net.javaguides.postgresql.exception;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(value = HttpStatus.NOT_FOUND)
public class ResourceNotFoundException extends Exception{

	private static final long serialVersionUID = 1L;

	public ResourceNotFoundException(String message){
    	super(message);
    }
}

Customizing Error Response Structure

Let's create ErrorDetails class with the following content to it:
package net.javaguides.postgresql.exception;

import java.util.Date;

public class ErrorDetails {
	private Date timestamp;
	private String message;
	private String details;

	public ErrorDetails(Date timestamp, String message, String details) {
		super();
		this.timestamp = timestamp;
		this.message = message;
		this.details = details;
	}

	public Date getTimestamp() {
		return timestamp;
	}

	public String getMessage() {
		return message;
	}

	public String getDetails() {
		return details;
	}
}

GlobalExceptionHandler Class

To use ErrorDetails to return the error response, let’s create a GlobalExceptionHandler class annotated with @ControllerAdvice annotation. This class handles exception-specific and global exceptions in a single place.
package net.javaguides.postgresql.exception;

import java.util.Date;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

@ControllerAdvice
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
	@ExceptionHandler(ResourceNotFoundException.class)
	public ResponseEntity<?> resourceNotFoundException(ResourceNotFoundException ex, WebRequest request) {
		ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), request.getDescription(false));
		return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
	}

	@ExceptionHandler(Exception.class)
	public ResponseEntity<?> globleExcpetionHandler(Exception ex, WebRequest request) {
		ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), request.getDescription(false));
		return new ResponseEntity<>(errorDetails, HttpStatus.INTERNAL_SERVER_ERROR);
	}
}

Running Application

This spring boot application has an entry point Java class called Application.java with the public static void main(String[] args) method, which you can run to start the application.
import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}
@SpringBootApplication is a convenience annotation that adds all of the following:
  • @Configuration tags the class as a source of bean definitions for the application context.
  • @EnableAutoConfiguration tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.
  • Normally you would add @EnableWebMvc for a Spring MVC app, but Spring Boot adds it automatically when it sees spring-webmvc on the classpath. This flags the application as a web application and activates key behaviors such as setting up a DispatcherServlet.
  • @ComponentScan tells Spring to look for other components, configurations, and services in the hello package, allowing it to find the controllers.
The main() method uses Spring Boot’s SpringApplication.run() method to launch an application.

The PostgreSQL database looks like this:

Integration Testing for REST APIs

There is a separate beautiful article for integration testing for REST APIs on:
>> Spring Boot 2 REST APIs Integration Testing

Testing CRUD REST APIs via Postman Client

1. Create Employee REST API


HTTP Method: POST 
Note that request and response JSON in the above diagram, the response contains database auto-generated id.

2. Get Employee by ID REST API

HTTP Method: GET 

3. Get all Employees REST API

HTTP Method: GET 

4. Update Employee REST API

HTTP Method: GET 

5. Delete Employee REST API

HTTP Method: DELETE 

Source code on GitHub

The source code of this tutorial is available on my GitHub Repository
>> https://github.com/RameshMF/spring-boot-tutorial/tree/master/springboot-postgresql-jpa-hibernate-crud-example

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