Development: Convert classes into records

[krusche]

Checklist

General

• I tested all changes and their related features with all corresponding user types on a test server.
• This is a small issue that I tested locally and was confirmed by another developer on a test server.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• I chose a title conforming to the naming conventions for pull requests.

Server

• Important: I implemented the changes with a very good performance and prevented too many (unnecessary) database calls.
• I strictly followed the server coding and design guidelines.
• I documented the Java code using JavaDoc style.

Motivation and Context

The main motivation for this change is to take advantage of records, which were introduced in Java 14 and formally standardised in Java 16. Records provide a more concise and readable way to define immutable data carriers, which is the main purpose of DTOs.

• Conciseness: Records significantly reduce boilerplate code. DTOs often require multiple lines of code to define fields, constructors, accessors, equals(), hashCode(), and toString() methods. With records, all of these are automatically provided by the compiler.
• Immutability: Records are immutable by default. This aligns with the design principles of DTOs, which should represent data snapshots without exposing mutability.
• Readability: By removing boilerplate code, records make the DTO definitions cleaner and more focused on the actual data they carry, improving readability and maintainability.
• Performance: The auto-generated methods in records are optimized by the compiler, potentially offering better performance characteristics for equals(), hashCode(), and toString().

Description

• Refactored multiple DTO classes in the project to use Java records.
• Added an architecture test that prevents the addition of new DTO classes.
• Updated relevant test cases to reflect the changes.

Steps for Testing

Prerequisites:

• 1 Instructor

• 1 Student

• 1 Tutor

• 1 Empty Course

• This PR is best tested locally, as you have access to the server's logs there.

• Look out for Bad Requests and Nullpointer Exceptions. They indicate that a Collection type that was never null by default before might be able to be null now.

• Given the changed DTOs, try to break the communication between the client and the server (e.g. Write a complaint as a student and then answer it as an instructor to test the AssessmentUpdateDTO etc.). Please make sure to add what you've tested into your review description.

• Likely edge cases include empty collections (e.g. an AssessmentUpdate with no feedbacks). The classes may have set these values to an empty collection by default, but the records do not, leading to potential errors when iterating directly over collections elsewhere in the code without first checking them for nullity.

Testserver States

Note

These badges show the state of the test servers.
Green = Currently available, Red = Currently locked

Review Progress

Code Review

• Code Review 1
• Code Review 2

Manual Tests

• Test 1
• Test 2

Exam Mode Test

• Test 1
• Test 2

Test Coverage

[rstief]

Code LGTM overall. I have some suggestions for improvements, but those can also be added in a follow-up.

Key Points (for the future):

• IMO DTOs should support null values for collections, so we should remove the compact constructors setting empty collections
• IMO we should use of(...) methods in the DTO rather than asDTO(...) methods in the entity

[JohannesWt]

Code looks good - few (maybe optional/debatable) changes explained in the comments

[laadvo]

Tested participation and assessment of programming, text, modeling, and file upload exercises locally. Working as expected, did not encounter any null pointers or bad requests

[rstief]

Code LGTM, thanks for implementing my many change requests 🙏🙏🙏

[DominikRemo]

Tested in testing session on TS5. Empty commits (empty additions/deletions/completely empty commits) work for programming exercises and empty submissions for all other exercise types also work (tested as part of an exam)

[undernagruzez]

tested during a testing session, works as expected for full on time submissions
found 2 issues, but guess they are not related to this pr

1. When I am registered for the exam(as a student) and click on the exam button, I see an error message(course overview page)
2. If the time on my machine differs from the server time, I cannot generate individual exams(as an instructor)

[az108]

tested in a testing session on ts5. Participated in a exam and tried various exercises and different scenarios. All work as expected.

[EneaGore]

Tested on testing session ts5. Works as expected.

[laadvo]

Tested in the testing session on ts5, competencies are still working as expected

[sarpsahinalp]

Tested locally works as expected