Refactor domain models to records and move exceptions to sub-package

- Convert Event and Rsvp from mutable POJOs to Java records
- Move all 8 exception classes to application.service.exception sub-package
- Add ArchUnit rule enforcing domain models must be records

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/main/java/de/fete/adapter/in/web/EventController.java

@@ -9,8 +9,8 @@ import de.fete.adapter.in.web.model.CreateRsvpResponse;
 import de.fete.adapter.in.web.model.GetAttendeesResponse;
 import de.fete.adapter.in.web.model.GetEventResponse;
 import de.fete.adapter.in.web.model.PatchEventRequest;
-import de.fete.application.service.EventNotFoundException;
-import de.fete.application.service.InvalidTimezoneException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidTimezoneException;
 import de.fete.domain.model.CreateEventCommand;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
@@ -78,11 +78,11 @@ public class EventController implements EventsApi {
     Event event = createEventUseCase.createEvent(command);
 
     var response = new CreateEventResponse();
-    response.setEventToken(event.getEventToken().value());
-    response.setOrganizerToken(event.getOrganizerToken().value());
-    response.setTitle(event.getTitle());
-    response.setDateTime(event.getDateTime());
-    response.setTimezone(event.getTimezone().getId());
+    response.setEventToken(event.eventToken().value());
+    response.setOrganizerToken(event.organizerToken().value());
+    response.setTitle(event.title());
+    response.setDateTime(event.dateTime());
+    response.setTimezone(event.timezone().getId());
 
     return ResponseEntity.status(HttpStatus.CREATED).body(response);
   }
@@ -94,16 +94,16 @@ public class EventController implements EventsApi {
         .orElseThrow(() -> new EventNotFoundException(eventToken));
 
     var response = new GetEventResponse();
-    response.setEventToken(event.getEventToken().value());
-    response.setTitle(event.getTitle());
-    response.setDescription(event.getDescription());
-    response.setDateTime(event.getDateTime());
-    response.setTimezone(event.getTimezone().getId());
-    response.setLocation(event.getLocation());
+    response.setEventToken(event.eventToken().value());
+    response.setTitle(event.title());
+    response.setDescription(event.description());
+    response.setDateTime(event.dateTime());
+    response.setTimezone(event.timezone().getId());
+    response.setLocation(event.location());
     response.setAttendeeCount(
         (int) countAttendeesByEventUseCase.countByEvent(evtToken));
-    response.setCancelled(event.isCancelled());
-    response.setCancellationReason(event.getCancellationReason());
+    response.setCancelled(event.cancelled());
+    response.setCancellationReason(event.cancellationReason());
 
     return ResponseEntity.ok(response);
   }
@@ -145,8 +145,8 @@ public class EventController implements EventsApi {
     Rsvp rsvp = createRsvpUseCase.createRsvp(evtToken, createRsvpRequest.getName());
 
     var response = new CreateRsvpResponse();
-    response.setRsvpToken(rsvp.getRsvpToken().value());
-    response.setName(rsvp.getName());
+    response.setRsvpToken(rsvp.rsvpToken().value());
+    response.setName(rsvp.name());
 
     return ResponseEntity.status(HttpStatus.CREATED).body(response);
   }

backend/src/main/java/de/fete/adapter/in/web/GlobalExceptionHandler.java

@@ -1,13 +1,13 @@
 package de.fete.adapter.in.web;
 
-import de.fete.application.service.EventAlreadyCancelledException;
-import de.fete.application.service.EventCancelledException;
-import de.fete.application.service.EventExpiredException;
-import de.fete.application.service.EventNotFoundException;
-import de.fete.application.service.ExpiryDateBeforeEventException;
-import de.fete.application.service.ExpiryDateInPastException;
-import de.fete.application.service.InvalidOrganizerTokenException;
-import de.fete.application.service.InvalidTimezoneException;
+import de.fete.application.service.exception.EventAlreadyCancelledException;
+import de.fete.application.service.exception.EventCancelledException;
+import de.fete.application.service.exception.EventExpiredException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.ExpiryDateBeforeEventException;
+import de.fete.application.service.exception.ExpiryDateInPastException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
+import de.fete.application.service.exception.InvalidTimezoneException;
 import java.net.URI;
 import java.util.List;
 import java.util.Map;

backend/src/main/java/de/fete/adapter/in/web/SpaController.java

@@ -86,11 +86,11 @@ public class SpaController {
 
   private Map<String, String> buildEventMeta(Event event, String baseUrl) {
     var tags = new LinkedHashMap<String, String>();
-    String title = truncateTitle(event.getTitle());
+    String title = truncateTitle(event.title());
     String description = formatDescription(event);
     tags.put("og:title", title);
     tags.put("og:description", description);
-    tags.put("og:url", baseUrl + "/events/" + event.getEventToken().value());
+    tags.put("og:url", baseUrl + "/events/" + event.eventToken().value());
     tags.put("og:type", "website");
     tags.put("og:site_name", GENERIC_TITLE);
     tags.put("og:image", baseUrl + "/og-image.png");
@@ -138,16 +138,16 @@ public class SpaController {
   }
 
   private String formatDescription(Event event) {
-    ZonedDateTime zoned = event.getDateTime().atZoneSameInstant(event.getTimezone());
+    ZonedDateTime zoned = event.dateTime().atZoneSameInstant(event.timezone());
     var sb = new StringBuilder();
     sb.append("📅 ").append(zoned.format(DATE_FORMAT));
 
-    if (event.getLocation() != null && !event.getLocation().isBlank()) {
-      sb.append(" · 📍 ").append(event.getLocation());
+    if (event.location() != null && !event.location().isBlank()) {
+      sb.append(" · 📍 ").append(event.location());
     }
 
-    if (event.getDescription() != null && !event.getDescription().isBlank()) {
-      sb.append(" — ").append(event.getDescription());
+    if (event.description() != null && !event.description().isBlank()) {
+      sb.append(" — ").append(event.description());
     }
 
     String result = sb.toString();

backend/src/main/java/de/fete/adapter/out/persistence/EventPersistenceAdapter.java

@@ -38,35 +38,34 @@ public class EventPersistenceAdapter implements EventRepository {
 
   private EventJpaEntity toEntity(Event event) {
     var entity = new EventJpaEntity();
-    entity.setId(event.getId());
-    entity.setEventToken(event.getEventToken().value());
-    entity.setOrganizerToken(event.getOrganizerToken().value());
-    entity.setTitle(event.getTitle());
-    entity.setDescription(event.getDescription());
-    entity.setDateTime(event.getDateTime());
-    entity.setTimezone(event.getTimezone().getId());
-    entity.setLocation(event.getLocation());
-    entity.setExpiryDate(event.getExpiryDate());
-    entity.setCreatedAt(event.getCreatedAt());
-    entity.setCancelled(event.isCancelled());
-    entity.setCancellationReason(event.getCancellationReason());
+    entity.setId(event.id());
+    entity.setEventToken(event.eventToken().value());
+    entity.setOrganizerToken(event.organizerToken().value());
+    entity.setTitle(event.title());
+    entity.setDescription(event.description());
+    entity.setDateTime(event.dateTime());
+    entity.setTimezone(event.timezone().getId());
+    entity.setLocation(event.location());
+    entity.setExpiryDate(event.expiryDate());
+    entity.setCreatedAt(event.createdAt());
+    entity.setCancelled(event.cancelled());
+    entity.setCancellationReason(event.cancellationReason());
     return entity;
   }
 
   private Event toDomain(EventJpaEntity entity) {
-    var event = new Event();
-    event.setId(entity.getId());
-    event.setEventToken(new EventToken(entity.getEventToken()));
-    event.setOrganizerToken(new OrganizerToken(entity.getOrganizerToken()));
-    event.setTitle(entity.getTitle());
-    event.setDescription(entity.getDescription());
-    event.setDateTime(entity.getDateTime());
-    event.setTimezone(ZoneId.of(entity.getTimezone()));
-    event.setLocation(entity.getLocation());
-    event.setExpiryDate(entity.getExpiryDate());
-    event.setCreatedAt(entity.getCreatedAt());
-    event.setCancelled(entity.isCancelled());
-    event.setCancellationReason(entity.getCancellationReason());
-    return event;
+    return new Event(
+        entity.getId(),
+        new EventToken(entity.getEventToken()),
+        new OrganizerToken(entity.getOrganizerToken()),
+        entity.getTitle(),
+        entity.getDescription(),
+        entity.getDateTime(),
+        ZoneId.of(entity.getTimezone()),
+        entity.getLocation(),
+        entity.getExpiryDate(),
+        entity.getCreatedAt(),
+        entity.isCancelled(),
+        entity.getCancellationReason());
   }
 }

backend/src/main/java/de/fete/adapter/out/persistence/RsvpPersistenceAdapter.java

@@ -43,19 +43,18 @@ public class RsvpPersistenceAdapter implements RsvpRepository {
 
   private RsvpJpaEntity toEntity(Rsvp rsvp) {
     var entity = new RsvpJpaEntity();
-    entity.setId(rsvp.getId());
-    entity.setRsvpToken(rsvp.getRsvpToken().value());
-    entity.setEventId(rsvp.getEventId());
-    entity.setName(rsvp.getName());
+    entity.setId(rsvp.id());
+    entity.setRsvpToken(rsvp.rsvpToken().value());
+    entity.setEventId(rsvp.eventId());
+    entity.setName(rsvp.name());
     return entity;
   }
 
   private Rsvp toDomain(RsvpJpaEntity entity) {
-    var rsvp = new Rsvp();
-    rsvp.setId(entity.getId());
-    rsvp.setRsvpToken(new RsvpToken(entity.getRsvpToken()));
-    rsvp.setEventId(entity.getEventId());
-    rsvp.setName(entity.getName());
-    return rsvp;
+    return new Rsvp(
+        entity.getId(),
+        new RsvpToken(entity.getRsvpToken()),
+        entity.getEventId(),
+        entity.getName());
   }
 }

backend/src/main/java/de/fete/application/service/EventService.java

@@ -1,5 +1,8 @@
 package de.fete.application.service;
 
+import de.fete.application.service.exception.EventAlreadyCancelledException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
 import de.fete.domain.model.CreateEventCommand;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
@@ -34,16 +37,19 @@ public class EventService implements CreateEventUseCase, GetEventUseCase, Update
   public Event createEvent(CreateEventCommand command) {
     LocalDate expiryDate = command.dateTime().toLocalDate().plusDays(EXPIRY_DAYS_AFTER_EVENT);
 
-    var event = new Event();
-    event.setEventToken(EventToken.generate());
-    event.setOrganizerToken(OrganizerToken.generate());
-    event.setTitle(command.title());
-    event.setDescription(command.description());
-    event.setDateTime(command.dateTime());
-    event.setTimezone(command.timezone());
-    event.setLocation(command.location());
-    event.setExpiryDate(expiryDate);
-    event.setCreatedAt(OffsetDateTime.now(clock));
+    var event = new Event(
+        null,
+        EventToken.generate(),
+        OrganizerToken.generate(),
+        command.title(),
+        command.description(),
+        command.dateTime(),
+        command.timezone(),
+        command.location(),
+        expiryDate,
+        OffsetDateTime.now(clock),
+        false,
+        null);
 
     return eventRepository.save(event);
   }
@@ -65,16 +71,14 @@ public class EventService implements CreateEventUseCase, GetEventUseCase, Update
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
 
-    if (!event.getOrganizerToken().equals(organizerToken)) {
+    if (!event.organizerToken().equals(organizerToken)) {
       throw new InvalidOrganizerTokenException();
     }
 
-    if (event.isCancelled()) {
+    if (event.cancelled()) {
       throw new EventAlreadyCancelledException(eventToken.value());
     }
 
-    event.setCancelled(true);
-    event.setCancellationReason(reason);
-    eventRepository.save(event);
+    eventRepository.save(event.withCancellation(true, reason));
   }
 }

backend/src/main/java/de/fete/application/service/RsvpService.java

@@ -1,5 +1,9 @@
 package de.fete.application.service;
 
+import de.fete.application.service.exception.EventCancelledException;
+import de.fete.application.service.exception.EventExpiredException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.OrganizerToken;
@@ -42,18 +46,15 @@ public class RsvpService
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
 
-    if (event.isCancelled()) {
+    if (event.cancelled()) {
       throw new EventCancelledException(eventToken.value());
     }
 
-    if (!event.getExpiryDate().isAfter(LocalDate.now(clock))) {
+    if (!event.expiryDate().isAfter(LocalDate.now(clock))) {
       throw new EventExpiredException(eventToken.value());
     }
 
-    var rsvp = new Rsvp();
-    rsvp.setRsvpToken(RsvpToken.generate());
-    rsvp.setEventId(event.getId());
-    rsvp.setName(name.strip());
+    var rsvp = new Rsvp(null, RsvpToken.generate(), event.id(), name.strip());
 
     return rsvpRepository.save(rsvp);
   }
@@ -63,14 +64,14 @@ public class RsvpService
   public void cancelRsvp(EventToken eventToken, RsvpToken rsvpToken) {
     eventRepository.findByEventToken(eventToken)
         .ifPresent(event ->
-            rsvpRepository.deleteByEventIdAndRsvpToken(event.getId(), rsvpToken));
+            rsvpRepository.deleteByEventIdAndRsvpToken(event.id(), rsvpToken));
   }
 
   @Override
   public long countByEvent(EventToken eventToken) {
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
-    return rsvpRepository.countByEventId(event.getId());
+    return rsvpRepository.countByEventId(event.id());
   }
 
   @Override
@@ -78,12 +79,12 @@ public class RsvpService
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
 
-    if (!event.getOrganizerToken().equals(organizerToken)) {
+    if (!event.organizerToken().equals(organizerToken)) {
       throw new InvalidOrganizerTokenException();
     }
 
-    return rsvpRepository.findByEventId(event.getId()).stream()
-        .map(Rsvp::getName)
+    return rsvpRepository.findByEventId(event.id()).stream()
+        .map(Rsvp::name)
         .toList();
   }
 }

backend/src/main/java/de/fete/application/service/exception/EventAlreadyCancelledException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.util.UUID;
 

backend/src/main/java/de/fete/application/service/exception/EventCancelledException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.util.UUID;
 

backend/src/main/java/de/fete/application/service/exception/EventExpiredException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.util.UUID;
 

backend/src/main/java/de/fete/application/service/exception/EventNotFoundException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.util.UUID;
 

backend/src/main/java/de/fete/application/service/exception/ExpiryDateBeforeEventException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.time.LocalDate;
 import java.time.OffsetDateTime;

backend/src/main/java/de/fete/application/service/exception/ExpiryDateInPastException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.time.LocalDate;
 

backend/src/main/java/de/fete/application/service/exception/InvalidOrganizerTokenException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 /** Thrown when an invalid organizer token is provided. */
 public class InvalidOrganizerTokenException extends RuntimeException {

backend/src/main/java/de/fete/application/service/exception/InvalidTimezoneException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 /** Thrown when an invalid IANA timezone ID is provided. */
 public class InvalidTimezoneException extends RuntimeException {

backend/src/main/java/de/fete/application/service/exception/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Application-layer exceptions thrown by service use case implementations.
+ */
+package de.fete.application.service.exception;

backend/src/main/java/de/fete/domain/model/Event.java

@@ -5,138 +5,26 @@ import java.time.OffsetDateTime;
 import java.time.ZoneId;
 
 /** Domain entity representing an event. */
-public class Event {
+public record Event(
+    Long id,
+    EventToken eventToken,
+    OrganizerToken organizerToken,
+    String title,
+    String description,
+    OffsetDateTime dateTime,
+    ZoneId timezone,
+    String location,
+    LocalDate expiryDate,
+    OffsetDateTime createdAt,
+    boolean cancelled,
+    String cancellationReason
+) {
 
-  private Long id;
-  private EventToken eventToken;
-  private OrganizerToken organizerToken;
-  private String title;
-  private String description;
-  private OffsetDateTime dateTime;
-  private ZoneId timezone;
-  private String location;
-  private LocalDate expiryDate;
-  private OffsetDateTime createdAt;
-  private boolean cancelled;
-  private String cancellationReason;
-
-  /** Returns the internal database ID. */
-  public Long getId() {
-    return id;
-  }
-
-  /** Sets the internal database ID. */
-  public void setId(Long id) {
-    this.id = id;
-  }
-
-  /** Returns the public event token. */
-  public EventToken getEventToken() {
-    return eventToken;
-  }
-
-  /** Sets the public event token. */
-  public void setEventToken(EventToken eventToken) {
-    this.eventToken = eventToken;
-  }
-
-  /** Returns the secret organizer token. */
-  public OrganizerToken getOrganizerToken() {
-    return organizerToken;
-  }
-
-  /** Sets the secret organizer token. */
-  public void setOrganizerToken(OrganizerToken organizerToken) {
-    this.organizerToken = organizerToken;
-  }
-
-  /** Returns the event title. */
-  public String getTitle() {
-    return title;
-  }
-
-  /** Sets the event title. */
-  public void setTitle(String title) {
-    this.title = title;
-  }
-
-  /** Returns the event description. */
-  public String getDescription() {
-    return description;
-  }
-
-  /** Sets the event description. */
-  public void setDescription(String description) {
-    this.description = description;
-  }
-
-  /** Returns the event date and time with UTC offset. */
-  public OffsetDateTime getDateTime() {
-    return dateTime;
-  }
-
-  /** Sets the event date and time. */
-  public void setDateTime(OffsetDateTime dateTime) {
-    this.dateTime = dateTime;
-  }
-
-  /** Returns the IANA timezone. */
-  public ZoneId getTimezone() {
-    return timezone;
-  }
-
-  /** Sets the IANA timezone. */
-  public void setTimezone(ZoneId timezone) {
-    this.timezone = timezone;
-  }
-
-  /** Returns the event location. */
-  public String getLocation() {
-    return location;
-  }
-
-  /** Sets the event location. */
-  public void setLocation(String location) {
-    this.location = location;
-  }
-
-  /** Returns the expiry date after which event data is deleted. */
-  public LocalDate getExpiryDate() {
-    return expiryDate;
-  }
-
-  /** Sets the expiry date. */
-  public void setExpiryDate(LocalDate expiryDate) {
-    this.expiryDate = expiryDate;
-  }
-
-  /** Returns the creation timestamp. */
-  public OffsetDateTime getCreatedAt() {
-    return createdAt;
-  }
-
-  /** Sets the creation timestamp. */
-  public void setCreatedAt(OffsetDateTime createdAt) {
-    this.createdAt = createdAt;
-  }
-
-  /** Returns whether the event has been cancelled. */
-  public boolean isCancelled() {
-    return cancelled;
-  }
-
-  /** Sets the cancelled flag. */
-  public void setCancelled(boolean cancelled) {
-    this.cancelled = cancelled;
-  }
-
-  /** Returns the cancellation reason, if any. */
-  public String getCancellationReason() {
-    return cancellationReason;
-  }
-
-  /** Sets the cancellation reason. */
-  public void setCancellationReason(String cancellationReason) {
-    this.cancellationReason = cancellationReason;
+  /** Returns a copy of this event with cancellation applied. */
+  public Event withCancellation(boolean cancelled, String cancellationReason) {
+    return new Event(
+        id, eventToken, organizerToken, title, description,
+        dateTime, timezone, location, expiryDate, createdAt,
+        cancelled, cancellationReason);
   }
 }

backend/src/main/java/de/fete/domain/model/Rsvp.java

@@ -1,50 +1,9 @@
 package de.fete.domain.model;
 
 /** Domain entity representing an RSVP. */
-public class Rsvp {
-
-  private Long id;
-  private RsvpToken rsvpToken;
-  private Long eventId;
-  private String name;
-
-  /** Returns the internal database ID. */
-  public Long getId() {
-    return id;
-  }
-
-  /** Sets the internal database ID. */
-  public void setId(Long id) {
-    this.id = id;
-  }
-
-  /** Returns the RSVP token. */
-  public RsvpToken getRsvpToken() {
-    return rsvpToken;
-  }
-
-  /** Sets the RSVP token. */
-  public void setRsvpToken(RsvpToken rsvpToken) {
-    this.rsvpToken = rsvpToken;
-  }
-
-  /** Returns the event ID this RSVP belongs to. */
-  public Long getEventId() {
-    return eventId;
-  }
-
-  /** Sets the event ID. */
-  public void setEventId(Long eventId) {
-    this.eventId = eventId;
-  }
-
-  /** Returns the guest's display name. */
-  public String getName() {
-    return name;
-  }
-
-  /** Sets the guest's display name. */
-  public void setName(String name) {
-    this.name = name;
-  }
-}
+public record Rsvp(
+    Long id,
+    RsvpToken rsvpToken,
+    Long eventId,
+    String name
+) {}