"status": 404 Error for POST Request in in Spring Boot CRUD

I developed Spring Boot CRUD application. The database I have connected is PostgreSQL. @GetMapping is working properly and an empty array of objects can be retrieved by the GET request. But in @PostMapping, the POST request gives a 404 error.

📌SpringRecapApplication.java

package com.example.SpringRecap;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@SpringBootApplication(exclude = SecurityAutoConfiguration.class)
//@RequestMapping("api/v1/customers")
//@EnableWebMvc
@RequestMapping(name = "api/v1/customers" ,method = RequestMethod.POST)

public class SpringRecapApplication {
    //dependency injection
    private static  CustomerRepository customerRepository;

    public SpringRecapApplication(CustomerRepository customerRepository) {
        this.customerRepository = customerRepository;
    }


    public static void main(String[] args) {
        SpringApplication.run(SpringRecapApplication.class, args);
    }

    @GetMapping
    public List<Customer> getCustomer() {

        return customerRepository.findAll();

    }

    record NewCustomerRequest(
            String name,
            String email,
            Integer age
    ) {
        @PostMapping
        public void addCustomer(@RequestBody NewCustomerRequest newCustomerRequest) {
            Customer customer = new Customer();
            customer.setAge(newCustomerRequest.age());
            customer.setName(newCustomerRequest.name());
            customer.setEmail(newCustomerRequest.email());
            customerRepository.save(customer);
        }
    }

}

customerRepository.save(customer); doesn’t allow to make the dependency injection final. ( private static CustomerRepository customerRepository;). IDEA suggests making it static. But it didn’t work. When I was using @RequestMapping("api/v1/customers"), a 405 error was received. Then I fixed that issue by doing as below,

 @RequestMapping(name = "api/v1/customers" ,method = RequestMethod.POST)

📌CustomerRepository.java

package com.example.SpringRecap;

import org.springframework.data.jpa.repository.JpaRepository;

public interface CustomerRepository extends JpaRepository<Customer,Integer> {
}

📌Customer.java

package com.example.SpringRecap;

import jakarta.persistence.*;

import java.util.Objects;

@Entity
public class Customer {
    @Id
    @SequenceGenerator(
            name = "customer_id_sequence",
            sequenceName = "customer_id_sequence",
            allocationSize = 1

    )
    @GeneratedValue(
            strategy = GenerationType.SEQUENCE,
            generator = "customer_id_sequence"

    )
    private Integer id;
    private String name;
    private String email;
    private Integer age;

    public Customer(Integer id, String name, String email, Integer age) {
        this.id = id;
        this.name = name;
        this.email = email;
        this.age = age;
    }

    public Customer() {

    }


    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Customer customer = (Customer) o;
        return Objects.equals(id, customer.id) && Objects.equals(name, customer.name) && Objects.equals(email, customer.email) && Objects.equals(age, customer.age);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, name, email, age);
    }

    @Override
    public String toString() {
        return "Customer{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", email='" + email + '\'' +
                ", age=" + age +
                '}';
    }
}

Postman:

Please put a comment if further information is needed to get the solution.

>Solution :

The problem with your code is that you specified the POST endpoint as part of your DTO and not as part of your controller. As your DTO is not a Spring managed bean, Spring won’t map the URL to your endpoint. Anyways, you should move your endpoints into a seperate class. Example:

@RestController
@RequestMapping("api/v1/customers")
public class CustomerController {

    private final CustomerRepository customerRepository;

    public SpringRecapApplication(CustomerRepository customerRepository) {
        this.customerRepository = customerRepository;
    }

    @GetMapping
    public List<Customer> getCustomer() {
        return customerRepository.findAll();
    }
    
    @PostMapping
    public void addCustomer(@RequestBody NewCustomerRequest newCustomerRequest) {
        Customer customer = new Customer();
        customer.setAge(newCustomerRequest.age());
        customer.setName(newCustomerRequest.name());
        customer.setEmail(newCustomerRequest.email());
        customerRepository.save(customer);
    }

    // Helper classes

    record NewCustomerRequest(String name, String email, Integer age) { }

}

It would be best if you moved your DTO in a seperate class as well. I recommend placing the DTOs in a dto package and your controllers in a controller package.

Two side notes: you shouldn’t expose your entities via your API. You should use DTOs for incoming and outgoing data. Check out lombok and mapstruct, they make this pretty easy.