Creating a RESTful Web Service with Spring Boot

Web services are applications that communicate over the internet using the HTTP protocol. There are many different types of web service architectures, but the principal idea across all designs is the same. In this book, we will create a RESTful web service: nowadays, a really popular design.

In this chapter, we will first create a RESTful web service using a controller class. Then, we will use Spring Data REST to create a RESTful web service that also provides all CRUD functionalities automatically, and document it with OpenAPI 3. After you have created a RESTful API for your application, you can implement the frontend using a JavaScript library such as React. We will be using the database application that we created in the previous chapter as a starting point.

In this chapter, we will cover the following topics:

• Basics of REST
• Creating a RESTful web service with Spring Boot
• Using Spring Data REST
...

Technical requirements

The Spring Boot application created in the previous chapters is required.

You will also need Postman, cURL, or another suitable tool for transferring data using various HTTP methods.

The following GitHub link will be required: https://github.com/PacktPublishing/Full-Stack-Development-with-Spring-Boot-3-and-React-Fourth-Edition/tree/main/Chapter04.

Basics of REST

Representational State Transfer (REST) is an architectural style for creating web services. REST is neither language- nor platform-dependent; different clients like mobile apps, browsers, and other services can communicate with each other. RESTful services can be scaled easily to fulfill increased demand.

REST is not a standard but a set of constraints, defined by Roy Fielding. The constraints are as follows:

• Stateless: The server shouldn’t hold any information about the client state.
• Client-server independence: The client and server should act independently. The server should not send any information without a request from the client.
• Cacheable: Many clients often request the same resources; therefore, caching should be applied to resources in order to improve performance.
• Uniform interface: Requests from different clients should look the same. Clients may include, for example, a browser, a Java application, and a mobile application...

Creating a RESTful web service with Spring Boot

In Spring Boot, all HTTP requests are handled by controller classes. To be able to create a RESTful web service, first, we have to create a controller class. We will create our own Java package for the controller:

1. Activate the root package in the Eclipse Project Explorer and right-click. Select New | Package from the menu. We will name our new package com.packt.cardatabase.web:

Figure 4.1: New Java package

2. Next, we will create a new controller class in a new web package. Activate the com.packt.cardatabase.web package in the Eclipse Project Explorer. Right-click and select New | Class from the menu; we will name our class CarController:

Figure 4.2: New Java class

3. Now, your project structure should look like the following screenshot:

   

   Figure 4.3: Project structure

   If you create classes in the wrong package accidentally, you can drag and drop the files between...

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In this chapter, we will first create a RESTful web service using the controller class. After that, we will demonstrate how to use Spring Data REST to create a RESTful web service that also provides all CRUD functionalities automatically. After you have created a RESTful API for your application, you can implement the frontend using a JavaScript library such as React. We will be using the database application that we created in the previous chapter as a starting point.Web services are applications that communicate over the internet using the HTTP protocol. There are many different types of web service architectures, but the principal idea across all designs is the same. In this book, we are creating...

Technical requirements

The Spring Boot application created in the previous chapters is required. Postman, cURL, or another suitable tool for transferring data using various HTTP methods is also necessary.The following GitHub link will also be required: https://github.com/PacktPublishing/Full-Stack-Development-with-Spring-Boot-3-and-React-Fourth-Edition/tree/main/Chapter04

Basics of REST

Representational State Transfer (REST) is an architectural style for creating web services. REST is not a standard, but it defines a set of constraints defined by Roy Fielding. The six constraints are as follows:

• Stateless: The server doesn't hold any information about the client state.
• Client: The client and server act independently. The server does not send any information without a request from the client.
• Cacheable: Many clients often request the same resources; therefore, it is useful to cache responses in order to improve performance.
• Uniform interface: Requests from different clients look the same. Clients may include, for example, a browser, a Java application, and a mobile application.
• Layered system: REST allows us to use a layered system architecture.
• Code on demand: This is an optional constraint.

The uniform interface is an important constraint, and it means that every REST architecture should have the following elements:

• Identification of resources...

Creating a RESTful web service

In Spring Boot, all HTTP requests are handled by controller classes. To be able to create a RESTful web service, first, we have to create a controller class. We will create our own Java package for the controller:

1. Activate the root package in the Eclipse Project Explorer and right-click. Select New | Package from the menu. We will name our new package com.packt.cardatabase.web:

   

   Figure 4.1: New Java package

2. Next, we will create a new controller class in a new web package. Activate the com.packt.cardatabase.web package in the Eclipse Project Explorer. Right-click and select New | Class from the menu; we will name our class CarController:

   

   Figure 4.2: New Java class

3. Now, your project structure should look like the following screenshot:

   

   Figure 4.3: Project structure

   IMPORTANT NOTE

   If you create classes in the wrong package accidentally, you can drag and drop the files between packages in the Eclipse Project Explorer. Sometimes, the Eclipse Project Explorer...

Using Spring Data REST

Spring Data REST (https://spring.io/projects/spring-data-rest) is part of the Spring Data project. It offers an easy and fast way to implement RESTful web services with Spring. Spring Data REST provides HATEOAS support that is an architectural principle which allows clients to navigate REST API dynamically using hypermedia links. To start using Spring Data REST, you have to add the following dependency to the build.gradle file:

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-data-rest'  
    developmentOnly 'org.springframework.boot:spring-boot-devtools'
    runtimeOnly 'org.mariadb.jdbc:mariadb-java-client'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

Refresh your Gradle project from Eclipse after...