CODEWITHSUNDEEP
javasqlspringrest
MicroLova
MicroLova

Reputation: 361

How to Design an Library Application with Rest Api including database

If you were designing an library application lets a citizen borrow & return books how would you design it from the database perspective.

I did this i created a Book Class 

@Entity
public class Book {
    private Integer id;
    private String title;
    private Integer numberOfCopies;

and when a user makes a request to citizen/borrow/{id} (With Book id The numberOfCopies variable adds one up or down

@GetMapping(path = "citizen/borrow/{id}", produces = {MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE})
public Book borrowBook(@PathVariable Integer id) {
    Book book = bookRepo.findById(id).orElseThrow(() -> new BookNotFoundException(id));
    Integer numberOfCopies = book.getNumberOfCopies();
    if (numberOfCopies == 0) throw new BookNotAvailableException();
    book.setNumberOfCopies(numberOfCopies - 1);
    bookRepo.save(book);
    return book;
}

how would you realize such an application? Is this good programming style or what you think?

Upvotes: 1

Views: 1332

Answers (1)

Ilya Sereb
Ilya Sereb

Reputation: 2571

First, according to REST practices, your endpoint (or resource) should be self-descriptive.

This path citizen/borrow/{id} looks like you are borrowing citizens, not books. It would make more sense to make resource like this: /v1/book/{id}/borrow as a POST request because modifying query will be executed.

Second, move your reusable logic into @Service layer.

I have a rule to never inject the repository into controllers. All saves and updates should be handled in the service layer and return a DTO (Data Transfer Object).

Third, handle your input in your controller layer.

Your @PathVariable may be null. This can cause problems deeper in the code. Why not just handle it right away and throw an exception from the beginning?

if (id == null)
    throw new new BookNotFoundException();

Upvotes: 1

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