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1. What we’ll build

2. Tools and Technologies Used

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

Step 1: Create a Spring Boot Application

Step 2: Maven dependencies

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.0.4</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>net.javaguides</groupId>
	<artifactId>springboot-backend</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>springboot-backend</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<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-devtools</artifactId>
			<scope>runtime</scope>
			<optional>true</optional>
		</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>

Step 3: Configuring PostgreSQL Database

First, you need to create a database in the PostgreSQL server. You can use the following command to create a database in the PostgreSQL server:

CREATE DATABASE employees;

Now, let’s configure the Spring Boot application to use PostgreSQL as our data source. You can do that simply by adding PostgreSQL database URL, username, and password in the src/main/resources/application.properties file.

Open the src/main/resources/application.properties file and add the following content to it:

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

Step 4: Create JPA Entity - Employee.java

package net.javaguides.springboot.model;
import jakarta.persistence.*;
@Entity
@Table(name = "employees")
public class Employee {
	
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private long id;
	
	@Column(name = "first_name")
	private String firstName;
	@Column(name = "last_name")
	private String lastName;
	
	@Column(name = "email_address")
	private String emailId;
	
	public Employee() {
		
	}
	
	public Employee(String firstName, String lastName, String emailId) {
		super();
		this.firstName = firstName;
		this.lastName = lastName;
		this.emailId = emailId;
	}
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	public String getEmailId() {
		return emailId;
	}
	public void setEmailId(String emailId) {
		this.emailId = emailId;
	}
}

package net.javaguides.springboot.repository;
import org.springframework.data.jpa.repository.JpaRepository;
import net.javaguides.springboot.model.Employee;
public interface EmployeeRepository extends JpaRepository<Employee, Long>{
}

package net.javaguides.springboot.controller;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.CrossOrigin;
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;
import net.javaguides.springboot.exception.ResourceNotFoundException;
import net.javaguides.springboot.model.Employee;
import net.javaguides.springboot.repository.EmployeeRepository;
@CrossOrigin(origins = "http://localhost:4200")
@RestController
@RequestMapping("/api/v1/")
public class EmployeeController {
	@Autowired
	private EmployeeRepository employeeRepository;
	
	// get all employees
	@GetMapping("/employees")
	public List<Employee> getAllEmployees(){
		return employeeRepository.findAll();
	}		
	
	// create employee rest api
	@PostMapping("/employees")
	public Employee createEmployee(@RequestBody Employee employee) {
		return employeeRepository.save(employee);
	}
	
	// get employee by id rest api
	@GetMapping("/employees/{id}")
	public ResponseEntity<Employee> getEmployeeById(@PathVariable Long id) {
		Employee employee = employeeRepository.findById(id)
				.orElseThrow(() -> new ResourceNotFoundException("Employee not exist with id :" + id));
		return ResponseEntity.ok(employee);
	}
	
	// update employee rest api
	
	@PutMapping("/employees/{id}")
	public ResponseEntity<Employee> updateEmployee(@PathVariable Long id, @RequestBody Employee employeeDetails){
		Employee employee = employeeRepository.findById(id)
				.orElseThrow(() -> new ResourceNotFoundException("Employee not exist with id :" + id));
		
		employee.setFirstName(employeeDetails.getFirstName());
		employee.setLastName(employeeDetails.getLastName());
		employee.setEmailId(employeeDetails.getEmailId());
		
		Employee updatedEmployee = employeeRepository.save(employee);
		return ResponseEntity.ok(updatedEmployee);
	}
	
	// delete employee rest api
	@DeleteMapping("/employees/{id}")
	public ResponseEntity<Map<String, Boolean>> deleteEmployee(@PathVariable Long id){
		Employee employee = employeeRepository.findById(id)
				.orElseThrow(() -> new ResourceNotFoundException("Employee not exist with id :" + id));
		
		employeeRepository.delete(employee);
		Map<String, Boolean> response = new HashMap<>();
		response.put("deleted", Boolean.TRUE);
		return ResponseEntity.ok(response);
	}
}

Step 8: Running Spring Boot Application

package net.javaguides.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class SpringbootBackendApplication {
	public static void main(String[] args) {
		SpringApplication.run(SpringbootBackendApplication.class, args);
	}
}

1. Create Employee REST API

2. Get Employee by ID REST API

3. Get all Employees REST API

4. Update Employee REST API

5. Delete Employee REST API