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.

>> Create Spring Boot Project With Spring Initializer
>> Create Spring Boot Project in Spring Tool Suite [STS]

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:

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:

Get Product By ID REST API:

Get All Products REST API:

Update 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

← Back to Spring Boot Tutorial