Building RESTful Services with Spring Boot

Using Spring MVC to Create REST Endpoints:

• Controller Class: Use @RestController annotation to create a REST controller.

• Mapping Requests: Use @GetMapping, @PostMapping, @PutMapping, @DeleteMapping for respective HTTP methods.

Example: Simple CRUD Operations for a Product Entity

1. Create a Product Entity:

   java

    package com.example.demo;
   
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;
   
    @Entity
    public class Product {
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        private Long id;
        private String name;
        private double price;
   
        // Getters and setters
    }
   

2. Create a ProductRepository:

   java

    package com.example.demo;
   
    import org.springframework.data.repository.CrudRepository;
   
    public interface ProductRepository extends CrudRepository<Product, Long> {
    }
   

3. Create a ProductController:

   java

    package com.example.demo;
   
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
   
    @RestController
    @RequestMapping("/products")
    public class ProductController {
   
        @Autowired
        private ProductRepository productRepository;
   
        @PostMapping
        public Product createProduct(@RequestBody Product product) {
            return productRepository.save(product);
        }
   
        @GetMapping("/{id}")
        public Product getProduct(@PathVariable Long id) {
            return productRepository.findById(id).orElse(null);
        }
   
        @PutMapping("/{id}")
        public Product updateProduct(@PathVariable Long id, @RequestBody Product productDetails) {
            Product product = productRepository.findById(id).orElse(null);
            if (product != null) {
                product.setName(productDetails.getName());
                product.setPrice(productDetails.getPrice());
                return productRepository.save(product);
            }
            return null;
        }
   
        @DeleteMapping("/{id}")
        public String deleteProduct(@PathVariable Long id) {
            productRepository.deleteById(id);
            return "Product deleted successfully!";
        }
    }
   

Handling HTTP Requests and Responses:

• Use @RequestBody to map the body of the request to a Java object.

• Use @PathVariable to extract values from the URI.

• Use @RequestParam for query parameters.