Spring Boot JPA - Application Setup


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As in previous chapter Environment Setup, we've imported the generated spring boot project in eclipse. Now let's create the following structure in src/main/java folder.

Project Structure
  • com.tutorialspoint.controller.EmployeeController − A REST Based Controller to implement REST based APIs.

  • com.tutorialspoint.entity.Employee − An entity class representing the corresponding table in database.

  • com.tutorialspoint.repository.EmployeeRepository − A Repository Interface to implement the CRUD operations on the database.

  • com.tutorialspoint.service.EmployeeService − A Service Class to implement the business opearations over repository functions.

  • com.tutorialspoint.springbooth2.SprintBootH2Application − A Spring Boot Application class.

SprintBootH2Application class is already present. We need to create the above packages and relevant classes and interface as shown below −

Entity - Entity.java

Following is the default code of Employee. It represents a Employee table with id, name, age and email columns.

package com.tutorialspoint.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table
public class Employee {
   @Id
   @Column
   private int id;

   @Column
   private String name;

   @Column
   private int age;

   @Column
   private String email;

   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   public int getAge() {
      return age;
   }
   public void setAge(int age) {
      this.age = age;
   }
   public String getEmail() {
      return email;
   }
   public void setEmail(String email) {
      this.email = email;
   }
}

Repository - EmployeeRepository.java

Following is the default code of Repository to implement CRUD operations on above entity, Employee.

package com.tutorialspoint.repository;

import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import com.tutorialspoint.entity.Employee;

@Repository
public interface EmployeeRepository extends CrudRepository<Employee, Integer>  {
}

Service - EmployeeService.java

Following is the default code of Service to implement operations over repository functions.

package com.tutorialspoint.service;

import java.util.ArrayList;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.tutorialspoint.entity.Employee;
import com.tutorialspoint.repository.EmployeeRepository;

@Service
public class EmployeeService {
   @Autowired
   EmployeeRepository repository;

   public Employee getEmployeeById(int id) {
      return repository.findById(id).get();
   }
   public List<Employee> getAllEmployees(){
      List<Employee> employees = new ArrayList<Employee>();
      repository.findAll().forEach(employee -> employees.add(employee));
      return employees;
   }
   public void saveOrUpdate(Employee employee) {
      repository.save(employee);
   }
   public void deleteEmployeeById(int id) {
      repository.deleteById(id);
   }
}

Controller - EmployeeController.java

Following is the default code of Controller to implement REST APIs.

package com.tutorialspoint.controller;

import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
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 com.tutorialspoint.entity.Employee;
import com.tutorialspoint.service.EmployeeService;

@RestController
@RequestMapping(path = "/emp")
public class EmployeeController {
   @Autowired
   EmployeeService employeeService;

   @GetMapping("/employees")
   public List<Employee> getAllEmployees(){
      return employeeService.getAllEmployees();
   }
   @GetMapping("/employee/{id}")
   public Employee getEmployee(@PathVariable("id") int id) {
      return employeeService.getEmployeeById(id);
   }
   @DeleteMapping("/employee/{id}")
   public void deleteEmployee(@PathVariable("id") int id) {
      employeeService.deleteEmployeeById(id);
   }
   @PostMapping("/employee")
   public void addEmployee(@RequestBody Employee employee) {
      employeeService.saveOrUpdate(employee);   
   }
   @PutMapping("/employee")
   public void updateEmployee(@RequestBody Employee employee) {
      employeeService.saveOrUpdate(employee);
   }	
}

Application - SprintBootH2Application.java

Following is the updated code of Application to use above classes.

package com.tutorialspoint.sprintbooth2;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@ComponentScan({"com.tutorialspoint.controller","com.tutorialspoint.service"})
@EntityScan("com.tutorialspoint.entity")
@EnableJpaRepositories("com.tutorialspoint.repository")
@SpringBootApplication
public class SprintBootH2Application {
   public static void main(String[] args) {
      SpringApplication.run(SprintBootH2Application.class, args);
   }
}

Run/Debug Configuration

Create following maven configuration in eclipse to run the springboot application with goal spring-boot:run. This configuration will help to run the REST APIs and we can test them using POSTMAN.

Maven Configuration

Run the application

In eclipse, run the Employee Application configuration. Eclipse console will show the similar output.

[INFO] Scanning for projects...
...
2021-07-24 20:51:14.823  INFO 9760 --- [restartedMain] c.t.s.SprintBootH2Application: 
Started SprintBootH2Application in 7.353 seconds (JVM running for 8.397)

Once server is up and running, Use Postman to make a POST request to add a record first.

Set the following parameters in POSTMAN.

  • HTTP Method - POST

  • URL - http://localhost:8080/emp/employee

  • BODY - An employee JSON

{  
   "id": "1",  
   "age": "35",  
   "name": "Julie",  
   "email": "julie@gmail.com"  
}   

Click on Send Button and check the response status to be OK. Now make a GET Request to get all records.

Set the following parameters in POSTMAN.

  • HTTP Method - GET

  • URL - http://localhost:8080/emp/employees

Click the send button and verify the response.

[{  
   "id": "1",  
   "age": "35",  
   "name": "Julie",  
   "email": "julie@gmail.com"  
}]   
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