Spring – REST Controller

Last Updated : 26 Nov, 2021

Spring Boot is built on the top of the spring and contains all the features of spring. And is becoming a favorite of developers these days because of its rapid production-ready environment which enables the developers to directly focus on the logic instead of struggling with the configuration and setup. Spring Boot is a microservice-based framework and making a production-ready application in it takes very little time. In this article, we will discuss what is REST controller is in the spring boot. There are mainly two controllers are used in the spring, controller and the second one is RestController with the help of @controller and @restcontroller annotations. The main difference between the @restcontroller and the @controller is that the @restcontroller combination of the @controller and @ResponseBody annotation.

RestController: RestController is used for making restful web services with the help of the @RestController annotation. This annotation is used at the class level and allows the class to handle the requests made by the client. Let’s understand @RestController annotation using an example. The RestController allows to handle all REST APIs such as GET, POST, Delete, PUT requests.

Spring Initializr is a web-based tool using which we can easily generate the structure of the Spring Boot project. It also provides various different features for the projects expressed in a metadata model. This model allows us to configure the list of dependencies that are supported by JVM. Here, we will create the structure of an application using a spring initializer and then use an IDE to create a sample GET route. Therefore, to do this, the following steps are followed sequentially as follows.

Step by Step Implementation

Step 1: Go to Spring Initializr

Fill in the details as per the requirements. For this application:

Project: Maven
Language: Java
Spring Boot: 2.2.8
Packaging: JAR
Java: 8
Dependencies: Spring Web

Step 2: Click on Generate which will download the starter project

Step 3: Extract the zip file. Now open a suitable IDE and then go to File > New > Project from existing sources > Spring-boot-app and select pom.xml. Click on import changes on prompt and wait for the project to sync as pictorially depicted below as follows:

Note: In the Import Project for Maven window, make sure you choose the same version of JDK which you selected while creating the project.

Step 4: Go to src > main > java > com.gfg.Spring.boot.app, create a java class with the name Controller and add the annotation @RestController and other class named as Details.

Details:

Java

public class Details { 
  
    // Creating an object of ArrayList 
    static ArrayList<Details> Data = new ArrayList<Details>(); 
    int number; 
    String name; 
    Details(int number, String name) 
    { 
        // This keyword refers  
          // to parent instance itself 
        this.number = number; 
        this.name = name; 
    } 
}

Controller:

Java

@RestController
// Class 
public class Controller { 
    // Constructor 
    Controller() 
    { 
        a.add(1); 
        a.add(2); 
    } 
  
    @GetMapping("/hello/{name}/{age}") 
    public void insert(@PathVariable("name") String name, 
                       @PathVariable("age") int age) 
    { 
  
        // Print and display name and age 
        System.out.println(name); 
        System.out.println(age); 
    } 
  
    // Creating an empty ArrayList 
    ArrayList<Integer> a = new ArrayList<>(); 
  
    // Annotation 
    @DeleteMapping("/hello/{id}") 
    // Method 
    public void deleteById(@PathVariable("id") int id) 
    { 
        a.remove(new Integer((id))); 
        print(); 
    } 
    
       // Handling post request 
    @PostMapping("/EnterDetails") 
    String insert(@RequestBody Details ob) 
    { 
        // Storing the incoming data in the list 
        Data.add(new Details(ob.number, ob.name)); 
  
        // Iterating using foreach loop 
        for (Details obd : Data) { 
            System.out.println(obd.name + " " + ob.number); 
        } 
        return "Data Inserted"; 
    } 
  
    // Method 
    void print() 
    { 
        for (int elements : a) { 
            System.out.print(elements); 
        } 
}