Spring Boot Gradle CRUD Example - CRUD REST APIs

In this tutorial, we will create a simple Spring Boot application using Gradle that performs CRUD (Create, Read, Update, Delete) operations on a Student entity. We will use Spring Data JPA to interact with a relational database.

Prerequisites

• JDK 17 or later
• Gradle
• Spring Boot (version 3.2+ recommended)
• IDE (IntelliJ IDEA, Eclipse, etc.)
• A relational database (e.g., H2, MySQL, PostgreSQL)

Step 1: Set Up a Spring Boot Project Using Spring Initializr

Use Spring Initializr to generate a new Spring Boot project with the following configuration:

• Project: Gradle Project
• Language: Java
• Spring Boot: 3.2.x
• Dependencies: Spring Web, Spring Data JPA, H2 Database (or your preferred database)

Download the generated project, unzip it, and open it in your IDE.

Project Structure

The basic structure of a Spring Boot project with Gradle looks like this:

my-spring-boot-app/
├── build.gradle
├── settings.gradle
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/demo/
│   │   │       └── DemoApplication.java
│   │   │       └── model/
│   │   │           └── Student.java
│   │   │       └── repository/
│   │   │           └── StudentRepository.java
│   │   │       └── service/
│   │   │           └── StudentService.java
│   │   │       └── controller/
│   │   │           └── StudentController.java
│   │   └── resources/
│   │       ├── application.properties
│   └── test/
│       └── java/
│           └── com/example/demo/
│               └── DemoApplicationTests.java
└── gradlew
└── gradlew.bat
└── gradle/
    └── wrapper/
        └── gradle-wrapper.properties

Step 2: Configuring build.gradle

Open the build.gradle file and configure it as follows:

plugins {
    id 'org.springframework.boot' version '3.2.0'
    id 'io.spring.dependency-management' version '1.1.0'
    id 'java'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    runtimeOnly 'com.h2database:h2' // Use H2 database for simplicity
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

test {
    useJUnitPlatform()
}

Step 3: Create the Student Entity

Create a Java class named Student in the src/main/java/com/example/demo/model directory.

package com.example.demo.model;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;

@Entity
public class Student {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private int age;

    // Constructors, getters, and setters

    public Student() {
    }

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long 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;
    }
}

Step 4: Create the Student Repository

Create a repository interface named StudentRepository in the src/main/java/com/example/demo/repository directory.

package com.example.demo.repository;

import com.example.demo.model.Student;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface StudentRepository extends JpaRepository<Student, Long> {
}

Step 5: Create the Student Service

Create a service class named StudentService in the src/main/java/com/example/demo/service directory.

package com.example.demo.service;

import com.example.demo.model.Student;
import com.example.demo.repository.StudentRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class StudentService {

    @Autowired
    private StudentRepository studentRepository;

    public List<Student> getAllStudents() {
        return studentRepository.findAll();
    }

    public Optional<Student> getStudentById(Long id) {
        return studentRepository.findById(id);
    }

    public Student createStudent(Student student) {
        return studentRepository.save(student);
    }

    public Optional<Student> updateStudent(Long id, Student student) {
        return studentRepository.findById(id).map(existingStudent -> {
            existingStudent.setName(student.getName());
            existingStudent.setAge(student.getAge());
            return studentRepository.save(existingStudent);
        });
    }

    public void deleteStudent(Long id) {
        studentRepository.deleteById(id);
    }
}

Step 6: Create the REST Controller

Create a controller class named StudentController in the src/main/java/com/example/demo/controller directory.

package com.example.demo.controller;

import com.example.demo.model.Student;
import com.example.demo.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Optional;

@RestController
@RequestMapping("/students")
public class StudentController {

    @Autowired
    private StudentService studentService;

    @GetMapping
    public List<Student> getAllStudents() {
        return studentService.getAllStudents();
    }

    @GetMapping("/{id}")
    public Optional<Student> getStudentById(@PathVariable Long id) {
        return studentService.getStudentById(id);
    }

    @PostMapping
    public Student createStudent(@RequestBody Student student) {
        return studentService.createStudent(student);
    }

    @PutMapping("/{id}")
    public Optional<Student> updateStudent(@PathVariable Long id, @RequestBody Student student) {
        return studentService.updateStudent(id, student);
    }

    @DeleteMapping("/{id}")
    public void deleteStudent(@PathVariable Long id) {
        studentService.deleteStudent(id);
    }
}

Step 7: Configure the Database

Open the src/main/resources/application.properties file and configure the H2 database.

# src/main/resources/application.properties

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true

Step 8: Running the Application

Using IDE

You can run the application directly from your IDE. Look for a "Run" or "Debug" option for the DemoApplication class.

Using Gradle

Alternatively, you can run the application using the Gradle wrapper. Open a terminal in the project root directory and run the following command:

For Unix/Linux/macOS:

./gradlew bootRun

For Windows:

gradlew.bat bootRun

Step 9: Verify CRUD Operations

Use a tool like Postman or curl to test the endpoints.

1. Create a Student:

   • URL: http://localhost:8080/students
   • Method: POST
   • Body:

     {
       "name": "John Doe",
       "age": 20
     }
     

2. Get All Students:

   • URL: http://localhost:8080/students
   • Method: GET

3. Get a Student by ID:

   • URL: http://localhost:8080/students/1
   • Method: GET

4. Update a Student:

   • URL: http://localhost:8080/students/1
   • Method: PUT
   • Body:

     {
       "name": "Jane Doe",
       "age": 21
     }
     

5. Delete a Student:

   • URL: http://localhost:8080/students/1
   • Method: DELETE

You should see the correct responses and verify that the data is stored, retrieved, updated, and deleted from the H2 database.

Conclusion

In this tutorial, you have learned how to create a Spring Boot application using Gradle that performs CRUD operations on a Student entity. We covered:

• Setting up a Spring Boot project with Gradle.
• Configuring the build.gradle file.
• Creating a Student entity, repository, service, and REST controller.
• Configuring the H2 database.
• Running the application and verifying CRUD operations using Postman or curl.

By following these steps, you can easily set up and manage Spring Boot projects using Gradle and perform CRUD operations on a relational database.