Workbook 9.4

The purpose of this workbook is to apply exception handling.

Launch the Starter Project

Custom Annotation

The starter project comes with the custom annotation @Score. It is identical to the annotation from the field validation section.

Error Response

The starter project also comes with an ErrorResponse template. It is identical to the template from the REST API section.

Global Exception Handler

The starter project also comes with a global exception handler. It inherits the method: handleMethodArgumentNotValid just like in workbook 8.3.

Task 1 (Review)

Apply validation constraints for:

• Course

  • If the submitted subject is blank: message = "Subject cannot be blank"
  • If the submitted code is blank: message = "Course code cannot be blank"
  • If the submitted description is blank: message = "Description cannot be blank"

• Student

  • If the submitted name is blank: message = "Name cannot be blank"
  • If the submitted birthDate is not in the past: message = "The birth date must be in the past"

• Grade

  • Apply the @Score constraint to the score field.

Task 2 (Review)

Inside the CourseController, GradeController, and StudentController, apply the @Valid annotation where needed.

Task 3 (Review)

Create a global exception handler class.

Task 4 (Review)

Inside handleMethodArgumentNotValid:

1. access the errors from the validation process through the binding result:

ex.getBindingResult().getAllErrors()

2. append every error into an ErrorResponse object.
3. Return the ErrorResponse with a status code of 400.

Task 5

Make a POST request on localhost:8080/student

{
    "birthDate": "2040-07-31"
}

Response: 400 Bad Request

{
    "timestamp": "05-08-2022 03:27:41",
    "message": [
        "Name cannot be blank",
        "The birth date must be in the past"
    ]
}

Task 6

Make a POST request on localhost:8080/grade/student/3/course/5

{
    "score": "R+"
}

Response: 400 Bad Request

{
    "timestamp": "05-08-2022 03:33:15",
    "message": [
        "The score is not valid"
    ]
}

Task 7

Make a POST request on localhost:8080/course

{
    "subject": "    ",
    "code": "     ",
    "description": "      "
}

Response: 400 Bad Request

{
    "timestamp": "05-08-2022 03:34:26",
    "message": [
        "Description cannot be blank",
        "Course code cannot be blank",
        "Subject cannot be blank"
    ]
}

Task 8

Create one exception handler method for an array of exceptions:

    @ExceptionHandler({CourseNotFoundException.class, GradeNotFoundException.class, StudentNotFoundException.class})
    public ResponseEntity<Object> handleResourceNotFoundException(RuntimeException ex) 

1. Return a status code of 404.
2. Return an ErrorResponse template of the error.

Task 9

Make a GET request on localhost:8080/student/10

Response: 404 Not Found

{
    "timestamp": "05-08-2022 03:37:35",
    "message": [
        "The student id '10' does not exist in our records"
    ]
}

Task 10

Make a GET request on localhost:8080/grade/student/10/course/10

Response: 404 Not Found

{
    "timestamp": "05-08-2022 03:38:52",
    "message": [
        "The grade with student id: '10' and course id: '10' does not exist in our records"
    ]
}

Task 11

An unsuccessful deletion will throw an EmptyResultDataAccessException. Create an exception handler for it:

    @ExceptionHandler(EmptyResultDataAccessException.class)
    public ResponseEntity<Object> handleDataAccessException(EmptyResultDataAccessException ex) {

    }

The method will return an ErrorResponse template with a message: Cannot delete non-existing resource, followed by a a status code of 404.

    ErrorResponse errorResponse = new ErrorResponse(Arrays.asList("Cannot delete non-existing resource"));  

Task 12

Make a DELETE request on localhost:8080/course/10

Response: 404 Not Found

{
    "timestamp": "05-08-2022 03:49:33",
    "message": [
        "Cannot delete non-existing resource"
    ]
}

Task 13

Attempting to save the same grade twice throws a DataIntegrityViolationException. Create an exception handler for it:

@ExceptionHandler(DataIntegrityViolationException.class)
public ResponseEntity<Object> handleDataIntegrityViolationException(DataIntegrityViolationException ex)

Return an ErrorResponse template with a message: Data Integrity Violation: we cannot process your request, followed by a status code of 400.

Task 14

Try saving the same grade twice.

{
    "timestamp": "05-08-2022 03:55:37",
    "message": [
        "Data Integrity Violation: we cannot process your request."
    ]
}

Good Luck!