What is a REST controller & Write a simple REST controller in Spring boot 3.xx

What is REST controller?

REST stands for REpresentation State Transfer.

A web controller is a logical component that is responsible for navigation of all operations related to a resource.

If you have a ProductController in your application, this ProductController will be responsible for: -

1. Creating new product

2. Updating existing product

3. Deleting a product

4. Getting a product

5. Getting all products

Write Product class

package wealthManager.models;

import java.io.Serializable;

public class Product implements Serializable {

    private final String name;

    private int price;

    public Product(String name, int price) {
        this.name = name;
        this.price = price;
    }

    public void setPrice(int price){
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public int getPrice() {
        return price;
    }
}

Write ProductController class

package wealthManager.rest;

import jakarta.annotation.PostConstruct;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PatchMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import wealthManager.models.Product;

import java.util.ArrayList;
import java.util.List;

@RestController
@RequestMapping("/product")
public class ProductController {

    private List<Product> productList = new ArrayList<>();

    @PostConstruct
    public void init() {
        productList.add(new Product("iPhone", 1000));
        productList.add(new Product("iPad", 500));
        productList.add(new Product("Macbook", 2000));
    }

    @GetMapping
    public List<Product> getProducts(){
        return productList;
    }

    @GetMapping("/{name}")
    public Product getProduct(@PathVariable("name") String name) {
        return productList.stream().filter(product -> product.getName().equals(name)).findFirst().orElse(null);
    }

    @DeleteMapping("/{name}")
    public Product deleteProduct(@PathVariable("name") String name) {
        Product product = getProduct(name);
        productList.removeIf(allProducts -> allProducts.getName().equals(name));
        return product;
    }

    @PostMapping("/{name}/{price}")
    public Product createProduct(@PathVariable("name") String name,
                                 @PathVariable("price") int price) {
        Product product = new Product(name, price);
        productList.add(product);
        return product;
    }

    @PatchMapping("/{name}/{price}")
    public Product updateProduct(@PathVariable("name") String name,
                                 @PathVariable("price") int price) {
        Product product = getProduct(name);
        product.setPrice(price);
        return product;
    }

}