Spring Boot CRUD Example without Database

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In this tutorial, we will learn how to build CRUD REST APIs using Spring boot but without the database.

Basically, we store and retrieve data to and from the in-memory object.

Checkout all Spring boot tutorials at https://www.javaguides.net/p/spring-boot-tutorial.html

Note that we are going to use the latest version of Spring Boot which is Spring Boot 3.

1. Creating a Spring Boot Application

There are many ways to create a Spring Boot application. You can refer below articles to create a Spring Boot application.
Refer to the next step to create a project packaging structure.

2. Create Project Packaging Structure

Here is the project packaging structure for your reference:
Spring Boot CRUD Example without Database

3. Maven Dependencies

Here is the pom.xml file for your reference:
<?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>3.0.0-SNAPSHOT</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>net.javaguides</groupId>
	<artifactId>springboot-crud-example-without-database</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>springboot-crud-example-without-database</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-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</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>
				<configuration>
					<excludes>
						<exclude>
							<groupId>org.projectlombok</groupId>
							<artifactId>lombok</artifactId>
						</exclude>
					</excludes>
				</configuration>
			</plugin>
		</plugins>
	</build>
	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<releases>
				<enabled>false</enabled>
			</releases>
		</repository>
	</repositories>
	<pluginRepositories>
		<pluginRepository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</pluginRepository>
		<pluginRepository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<releases>
				<enabled>false</enabled>
			</releases>
		</pluginRepository>
	</pluginRepositories>

</project>

4. Create Model - Product.java

Let's create a Product model class and add the following content to it:
package net.javaguides.springboot.model;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Product {
    private int id;
    private String name;
    private int quantity;
    private double price;
}

5. Create Repository - ProductRepository

We will perform CRUD operations on an in-memory using the ArrayList object.

Create ProductRepository and add the following content to it:
package net.javaguides.springboot.repository;

import net.javaguides.springboot.model.Product;
import org.springframework.stereotype.Repository;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

@Repository
public class ProductRepository {
    private List<Product> list = new ArrayList<Product>();

    public void createProducts() {
        list = List.of(
                new Product(1, "product 1", 10, 1000),
                new Product(2, "product 2", 20, 2000),
                new Product(3, "product 3", 30, 3000)
        );
    }

    public List<Product> getAllProducts() {
        return list;
    }

    public Product findById(int id){
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i).getId() == (id)) {
                return list.get(i);
            }
        }
        return null;
    }

    public List<Product> search(String name) {
        return list.stream().filter(x -> x.getName().startsWith(name)).collect(Collectors.toList());
    }

    public Product save(Product p) {
        Product product = new Product();
        product.setId(p.getId());
        product.setName(p.getName());
        product.setQuantity(p.getQuantity());
        product.setPrice(p.getPrice());
        list.add(product);
        return product;
    }

    public String delete(Integer id) {
        list.removeIf(x -> x.getId() == (id));
        return null;
    }

    public Product update(Product product) {
        int idx = 0;
        int id = 0;
        for (int i = 0; i < list.size(); i++) {
            if (list.get(i).getId() == (product.getId())) {
                id = product.getId();
                idx = i;
                break;
            }
        }

        Product product1 = new Product();
        product1.setId(id);
        product1.setName(product.getName());
        product1.setQuantity(product.getQuantity());
        product1.setPrice(product.getPrice());
        list.set(idx, product);
        return product1;
    }
}

6. Create Service - ProductService.java

Create a ProductService class and add the following content to it:
package net.javaguides.springboot.service;

import net.javaguides.springboot.model.Product;
import net.javaguides.springboot.repository.ProductRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class ProductService {
    @Autowired
    private ProductRepository repository;

    public Product saveProduct(Product product) {
        return repository.save(product);
    }

    public List<Product> getProducts() {
        return repository.getAllProducts();
    }

    public Product getProductById(int id) {
        return repository.findById(id);
    }

    public String deleteProduct(int id) {
        repository.delete(id);
        return "product removed !! " + id;
    }

    public Product updateProduct(Product product) {
       return repository.update(product);
    }
}

7. Create Controller - ProductController.java

Let's create the REST APIs for creating, retrieving, updating, and deleting a Product resource.

Let's create ProductController class and add the following content to it:
package net.javaguides.springboot.controller;

import net.javaguides.springboot.model.Product;
import net.javaguides.springboot.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/v1/products")
public class ProductController {

    @Autowired
    private ProductService service;

    @PostMapping
    public Product addProduct(@RequestBody Product product) {
        return service.saveProduct(product);
    }

    @GetMapping
    public List<Product> findAllProducts() {
        return service.getProducts();
    }

    @GetMapping("{id}")
    public Product findProductById(@PathVariable int id) {
        return service.getProductById(id);
    }

    @PutMapping
    public Product updateProduct(@RequestBody Product product) {
        return service.updateProduct(product);
    }

    @DeleteMapping("{id}")
    public String deleteProduct(@PathVariable int id) {
        return service.deleteProduct(id);
    }
}

8. Running the Spring Boot Application

We have successfully developed all the CRUD Rest APIs for the Product model. Now it's time to deploy our application in a servlet container(embedded tomcat). 
Two ways we can start the standalone Spring boot application. 
1. From the root directory of the application and type the following command to run it -
$ mvn spring-boot:run
2. From your IDE, run the SpringbootCrudExampleWithoutDatabaseApplication.main() method as a standalone Java class that will start the embedded Tomcat server on port 8080 and point the browser to http://localhost:8080/.

9. Demo

We use the Postman client tool to test the CRUD REST APIs.

Create Product REST API:

Create Product REST AP

Get Product By ID REST API:

Get Product By ID REST API:

Get All Products REST API:

Get All Products REST API:

Update Product REST API:

Update Product REST API:

Delete Product REST API:

Delete Product REST API:

10. Conclusion

In this tutorial, we have seen how to build CRUD REST APIs using Spring boot but without the database. Basically, we have used an in-memory object to store and retrieve the data.

Checkout all Spring boot tutorials at https://www.javaguides.net/p/spring-boot-tutorial.html

Related Spring and Spring Boot Tutorials/Guides:

Spring Boot Tutorials [500+] Spring Boot Testing Tutorial Spring Boot Microservice Tutorial Spring Boot Kafka Microservices Spring Boot + Apache Kafka Tutorial Spring Core Tutorial Spring MVC Tutorial Spring Data JPA Tutorial Spring Framework for Beginners Spring AOP Tutorial Spring Security Tutorial Spring Exceptions Tutorial Spring Boot Interview Questions Spring Boot Microservices Interview Questions Apache Kafka Tutorials Docker Tutorials and Guides Spring Boot RabbitMQ Tutorials Angular CRUD Example with Spring Boot Spring Boot + Angular 12 CRUD Full Stack Spring Boot + Angular 8 CRUD Full Stack Spring Boot + Angular 10 CRUD Full Stack Spring Boot + React JS CRUD Full Stack React JS ( React Hooks) + Spring Boot Spring Boot Thymeleaf CRUD Full Stack Spring Boot User Registration and Login Node Js + Express + MongoDB CRUD Vue JS + Spring Boot REST API Tutorial

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