Spring Boot + Microsoft SQL Server + JPA/Hibernate CRUD Restful API Tutorial

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In this tutorial, you will learn how to build CRUD (Create, Read, Update, Delete) RESTFul APIs using Spring Boot, Microsoft SQL Server, JPA/Hibernate, and Maven.

Spring Boot simplifies the process of switching between RDBMS. When utilizing Spring Data JPA in conjunction with an ORM technology like Hibernate, the persistence layer becomes nicely decoupled. Since Hibernate is being used, it inherently provides support for working with various database vendors without necessitating any changes to the underlying code.

Follow these quick three steps to configure the Microsoft SQL server in the Spring boot application with Spring Data JPA:

Step 1: Add Spring Data JPA Dependency 

Let's use Spring Data JPA with the below dependency:

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

Step 2: SQL Server Dependency 

Add below MS-SQL JDBC driver dependency in your pom.xml file:

		<dependency>
			<groupId>com.microsoft.sqlserver</groupId>
			<artifactId>mssql-jdbc</artifactId>
			<scope>runtime</scope>
		</dependency>

Step 3: Configure the MS-SQL Server in an application.properties file 

Configure Spring Boot to use an MS-SQL server database as our data source. We simply add the Microsoft SQL server URL, username, and password in the src/main/resources/application.properties file:

spring.datasource.url=jdbc:sqlserver://localhost;databaseName=employees
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql = true

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

That's all. Now you are good to go.

Let's develop a complete CRUD RESTFul API for a Simple Employee Management System using Spring Boot, Spring Data JPA (Hibernate), and Microsoft SQL database.

Table of Contents

1. What we’ll build?
2. Tools and Technologies Used
3. Creating and Importing a Project
4. The pom.xml File
5. Packaging Structure
6. Configuring MS-SQL Server Database
7. Create JPA Entity - Employee.java
8. Create Spring Data Repository - EmployeeRepository.java
9. Create Spring Rest Controller - EmployeeController.java
10. Exception(Error) Handling for RESTful Services
11. Running Application
12. Integration Testing for REST APIs
13. Testing REST APIs via Postman Client
14. Source code on GitHub Repository

1. What we’ll build

We will build CRUD RESTFul APIs for a Simple Employee Management System using Spring Boot, Spring Data JPA, and MS-SQL database. 

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

2. Tools and Technologies Used

• Spring Boot - 3+
• JDK - 17 or later
• Spring Framework - 6+
• Hibernate - 6+
• JPA
• Maven - 3.2+
• IDE - Eclipse or Spring Tool Suite (STS)
• Microsoft SQL Server - 4.0

3. Creating and Importing a Project

There are many ways to create a Spring Boot application. The simplest way is to use Spring Initializr, which is an online Spring Boot application generator.

Look at the above diagram, we have specified the following details:

• Generate: Maven Project
• Java Version: 17 (Default)
• Spring Boot:3.0.4
• Group: net.javaguides.mssq
• Artifact: springboot-mssql-jpa-hibernate-crud-example
• Name: springboot-mssql-jpa-hibernate-crud-example
• Description: springboot-mssql-jpa-hibernate-crud-example
• Package Name : net.javaguides.mssql
• Packaging: jar (This is the default value)
• Dependencies: Spring Web, Spring Data JPA

Once, all the details are entered, next, click on Generate Project button will generate a spring boot project and downloads it. Next, Unzip the downloaded zip file and import it into your favorite IDE.

4. Maven Dependencies

Make sure that you have the following Maven dependencies in your Spring Boot project:

                <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>com.microsoft.sqlserver</groupId>
			<artifactId>mssql-jdbc</artifactId>
			<scope>runtime</scope>
		</dependency>

5. Packaging Structure

Following is the packing structure of our Employee Management System -

6. Configuring MS-SQL Server Database

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

spring.datasource.url=jdbc:sqlserver://localhost;databaseName=employees
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql = true
# Hibernate ddl auto (create, create-drop, validate, update)
spring.jpa.hibernate.ddl-auto = update

7. Create JPA Entity - Employee.java

Let's create an Employee JPA entity and add the following code to it:

package net.javaguides.mssql.model;

import jakarta.persistence.*;

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

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    @Column(name = "first_name", nullable = false)
    private String firstName;
    @Column(name = "last_name", nullable = false)
    private String lastName;
    @Column(name = "email_address", nullable = false)
    private String emailId;

    public Employee() {

    }

    public Employee(String firstName, String lastName, String emailId) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.emailId = emailId;
    }
     //getter/setter methods
}

Explanation:

In Spring Data JPA, entities are objects that represent the data stored in a database table. JPA provides a set of annotations that can be used to map a Java class to a database table. 

@Entity: This annotation is used to mark a Java class as an entity. An entity is a lightweight persistence domain object that is mapped to a database table. This annotation is required for every entity class.

@Table: This annotation is used to specify the name of the database table that the entity is mapped to. By default, the name of the table is the same as the name of the entity class. If you want to use a different name, you can specify it using this annotation.

@Id: This annotation is used to mark a field in the entity class as the primary key. A primary key is a unique identifier for each row in the table. This annotation is required for every entity class and should be applied to one and only one field or property.

@Column: This annotation is used to map a field in the entity class to a column in the database table. By default, the name of the column is the same as the name of the field. If you want to use a different name, you can specify it using this annotation.

@GeneratedValue: This annotation is used to specify how the primary key is generated. There are several strategies available, such as AUTO, IDENTITY, SEQUENCE, and TABLE. By default, the strategy is AUTO, which means that the persistence provider will choose the appropriate strategy based on the underlying database.

8. Create Spring Data Repository - EmployeeRepository.java

package net.javaguides.mssql.repository;

import net.javaguides.mssql.model.Employee;
import org.springframework.data.jpa.repository.JpaRepository;

public interface EmployeeRepository extends JpaRepository<Employee, Long>{

}

By extending the JpaRepository interface, the EmployeeRepository interface inherits all the methods defined in JpaRepository, such as findAll(), findById(), save(), and deleteById(). These methods can be used to perform common CRUD operations on the Employee entity without having to write the actual SQL statements.

9. Exception(Error) Handling for RESTful Services

Spring Boot provides a good default implementation for exception handling for RESTful Services. Let’s quickly look at the default Exception Handling features provided by Spring Boot.

Let's create a ResourceNotFoundException.java class with the following code:

package net.guides.springboot2.crud.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);
    }
}

Let’s define an ErrorDetails response bean with the following code:

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;
    }
}

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.

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;

@ControllerAdvice
public class GlobalExceptionHandler {
    @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);
    }
}

10. Create Spring Rest Controller - EmployeeController.java

Let's create an EmployeeController Spring MVC controller and build CRUD REST APIs:

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

import jakarta.validation.Valid;

import net.javaguides.mssql.model.Employee;
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;

import net.javaguides.mssql.exception.ResourceNotFoundException;
import net.javaguides.mssql.repository.EmployeeRepository;

@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;
	}
}

Build Get All Employees REST API:

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

Get Employee By Id REST API:

	@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);
	}

Create Employee REST API:

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

Update Employee REST API:

	@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);
	}

Delete Employee REST API:

	@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;
	}

11. Running Application

This spring boot application has an entry point Java class called SpringBootCrudRestApplication.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.

12. Testing REST APIs via Postman Client

1. Create Employee REST API

HTTP Method: POST 

Request URL: http://localhost:8080/api/v1/employees 

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 

Request URL: http://localhost:8080/api/v1/employees/11

3. Get all Employees REST API

HTTP Method: GET 

Request URL: http://localhost:8080/api/v1/employees

4. Update Employee REST API

HTTP Method: GET 

Request URL: http://localhost:8080/api/v1/emploees/7

5. Delete Employee REST API

HTTP Method: DELETE 

Request URL: http://localhost:8080/api/v1/employees/11

13 Conclusion

In conclusion, this tutorial has demonstrated how to build a complete CRUD RESTful API for a simple Employee Management System using Spring Boot, Microsoft SQL Server, and JPA/Hibernate. 

We started by setting up creating the Employee entity and repository and then implementing the REST endpoints for CRUD operations. We also learned about JPA/Hibernate annotations such as @Entity, @Table, @Id, @Column, and @GeneratedValue, and how they are used to map entities to database tables and columns. Finally, we tested our API using Postman and verified that it works as expected. 

14. Source code on GitHub

The source code of this tutorial is available on my GitHub repository.

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