lesson10.md

Lesson 10: @DeleteMapping

Overview

The HTTP DELETE request deletes a record. The primary key of the record to be deleted can be sent as part of the request URI or the record itself can be sent as part of the request body.

JpaRepository inherits two methods of the CrudRepository for deleting a record.

• The delete method takes an entity to be deleted
• The deleteById method takes the primary key of the entity to be deleted.

They both have the same function, and internally the deleteById method calls the delete method:

void deleteById(ID id) { 
    delete(findById(id)); 
}

The difference lies in the way both methods respond when the entity to be deleted is not found.

• The deleteById method throws the EmptyResultDataAccessException
• The delete method throws a NoSuchElementException

In the PlayerService class, we create a service layer method called deletePlayer to handle delete functionality.

Inside the deletePlayer method, we call the repository method deleteById and pass the player’s id. The deleteById method internally calls the findById method, and then deletes the record.

public String deletePlayer(int id) {
    repo.deleteById(id);
    return "Deleted player with id: " + id;
}

To handle the exception thrown when the player record is not found, we can enclose the method call in a try catch block:

try {
    repo.deleteById(id);
} catch(Exception e) {
    return "Player with id " + id + "not found";
}

Demonstrated Concepts

Moving on to the controller layer, we create a method deletePlayer to handle the DELETE request. It maps to the endpoint /players/{id}, with id being the path variable. The REST controller will respond with a message informing the client of the success or failure. The method is annotated with @DeteleMapping.

The @PathVariable annotation binds the id path variable to the method parameter id.

@DeleteMapping("/players/{id}")
public String deletePlayer(@PathVariable int id) {
    //call service layer method 
}

The @DeleteMapping annotation is a shortcut annotation. It is the same as:

@RequestMapping(method = RequestMethod.DELETE)

The deletePlayer method will delegate the call to the service layer and pass the id received in the DELETE request. On success, the method will return the deleted player’s id by plugging the id received in the request.

If the player is not found in the database, the method will return with a message informing the client that the player was not found.

To test the new endpoint, launch the application and create a DELETE request in Postman. We provide the id of the player as part of the URI, so the request body will be empty.

Send two DELETE requests, first to localhost:8080/players/3. In this case, the REST controller responds with a success message.

Send the second DELETE request to localhost:8080/players/4 and the REST controller should respond that the player with id 4 is not found.

The results can be verified by using a GET request to /players. It can be seen that only 2 players remain in the database.