Spring boot api how to prevent duplicate data creation

Question

I have a POST API to create an entity called Person, and I check if person with the name and address exist or not, if not i create a person entity:

class Person {
    UUID id
    String name;
    String address
}

public void createPerson(String name, String addr){
    Person p = repository.findPersonByNameAndAddress(name, addr);
    if (p != null) {
        repository.create(name, addr);
    }
}

If a client calls the POST with same data at the same time I will end up creating two person with same name and address (but different ID). How can i prevent this from happening? I am using spring boot + JPA/Hibernate + postgres

Thanks!

Ranjith · Accepted Answer · 2019-03-24 05:34:04Z

3

Such constraints can be enforced only at the database layer. They cannot be handled at the application layer. If, as per your data model, two people cannot have the same name and address, you can add a unique constraint on (name, address) in your database.

ALTER TABLE person
  add CONSTRAINT person_name_address UNIQUE (name, address);

With such a constraint, one of the two API calls will result in a SQLIntegrityConstraintViolationException which you can handle accordingly.

answered Mar 24, 2019 at 5:34

Ranjith

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Comments

sf_ · Accepted Answer · 2020-04-23 19:35:52Z

0

You can fix it by either of two ways:

Define a unique key constraint for both name and address

Find person by name and address by ignoring case using existsByNameIgnoreCaseAndAddressIgnoreCase

class PersonDao {

   public void createPerson(String name, String addr) {
        boolean isExists = repository.existsByNameIgnoreCaseAndAddressIgnoreCase(name, addr);
        if (!isExists) {
            PersonEntity person = new PersonEntity();
            person.setName(name);
            person.setAddress(addr);
            repository.save(person);
        }
    }
}

edited Apr 23, 2020 at 19:35

sf_

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answered Mar 24, 2019 at 5:34

Gaurav Srivastav

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1 Comment

sf_ Over a year ago

Your second point won't work. If you will test it in concurrency environment (send at least 5 requests in the same time) - they all (or part of them) will reach isExists=false and try to create a new entity.

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