RESTful API Lab 4

Steps and Files

1. CustomerAlreadyExistsException
   • exception/CustomerAlreadyExistsException.java
2. CustomerRepository findByMobileNumber
   • repository/CustomerRepository.java
3. IAccountsService CustomerAlreadyExistsException
   • service/AccountsService.java
4. GlobalExceptionHandler
   • exception/GlobalExceptionHandler.java
5. Test the application

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Lab#4 Exception Handling –check if customer already exists

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The customers mobile phone number must be unique. In this lab we will check if a customer with the given phone number already exists and we will reject the request accordingly.

1. CustomerAlreadyExistsException

Add a package com.tus.accounts.exception with a class CustomerAlreadyExistsException

package com.tus.accounts.exception;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public class CustomerAlreadyExistsException extends RuntimeException {
    private static final long serialVersionUID = 1L;

    public CustomerAlreadyExistsException(String message) {
        super(message);
    }
}

2. CustomerRepository findByMobileNumber

In the CustomerRepository interface add a query to find a Customer based on the mobile number. (This may be in your file already).

package com.tus.accounts.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import com.tus.accounts.entity.Customer;
import java.util.Optional;

@Repository
public interface CustomerRepository extends JpaRepository<Customer, Long> {
    Optional<Customer> findByMobileNumber(String mobileNumber);
}

3. IAccountsService CustomerAlreadyExistsException

Now in the Service class add code that will throw the CustomerAlreadyExistsException.

public void createAccount(CustomerDto customerDto) {
        Customer customer = CustomerMapper.mapToCustomer(customerDto, new Customer());
        Optional<Customer> optionalcustomer = customerRepository.findByMobileNumber(customerDto.getMobileNumber());
        if (optionalcustomer.isPresent()) {
            throw new CustomerAlreadyExistsException(
                    "Customer already registered with given mobile Number " + customerDto.getMobileNumber());
        }
        customer.setCreatedAt(LocalDateTime.now());
        customer.setCreatedBy("default");
        customer.setUpdatedBy("default");
        customer.setUpdatedAt(LocalDateTime.now());

        Customer savedCustomer = customerRepository.save(customer
        accountsRepository.save(createNewAccount(savedCustomer));
    }

4. GlobalExceptionHandler

Add a class in the exception package called GlobalExceptionHandler. This will handle exceptions in one location rather than duplicating the handlng. It is annotated with @ControllerAdvice and will handle the exception when thrown by the controller.

package com.tus.accounts.exception;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.http.ResponseEntity;
import com.tus.accounts.dto.ErrorResponseDto;
import org.springframework.web.context.request.WebRequest;
import org.springframework.http.HttpStatus;
import java.time.LocalDateTime;

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(CustomerAlreadyExistsException.class)
    public ResponseEntity<ErrorResponseDto> handleCustomerAlreadyExistsException(
            CustomerAlreadyExistsException exception, WebRequest webRequest) {
        ErrorResponseDto errorResponseDTO = new ErrorResponseDto(webRequest.getDescription(false),
                HttpStatus.BAD_REQUEST, 
                exception.getMessage(), 
                LocalDateTime.now());
        return new ResponseEntity<>(errorResponseDTO, HttpStatus.BAD_REQUEST);
    }
}

5. Test the application

Add a customer. Customer is created successfully. Then add a customer with the same mobile number again. The request is rejected with error message as shown.