How to check entity is already created?
Just like validating the user email in any system you check if its already exists or not, in your case we need to check that we have no entity with the same attribute value exists:

$query = new EntityFieldQuery();

$query-&gt;entityCondition('entity_type', 'Fruit_Store')
  -&gt;entityCondition('bundle', 'store')
  // this is a condition for the entity field values
  -&gt;fieldCondition('field_title', 'value', 'spotlight', '=');

$result = $query-&gt;execute();

if (!empty($result['Fruit_Store'])) {
  // entity already exsits.
}
else{
  // add new entity
}


you can find more information about EntityFieldQuery in this page:

https://www.drupal.org/node/1343708