lesson

src/main/java/de/jottyfan/bico/modules/slot/SlotController.java

@@ -32,6 +32,7 @@ public class SlotController extends CommonController {
 	@GetMapping("/slot/{id}")
 	public String load(@PathVariable Integer id, Model model) {
 		model.addAttribute("bean", id == null ? new SlotBean() : service.loadSlot(id));
+		model.addAttribute("hasLesson", service.slotHasLesson(id));
 		return "/slot/item";
 	}
 

src/main/java/de/jottyfan/bico/modules/slot/SlotRepository.java

@@ -126,4 +126,20 @@ public class SlotRepository {
 			return null;
 		}
 	}
+
+	/**
+	 * return true if this slot already has at least one lesson
+	 *
+	 * @param slotId the ID of the slot
+	 * @return true or false
+	 */
+	public Boolean getHasLesson(Integer slotId) {
+		SelectConditionStep<TLessonRecord> sql = jooq
+		// @formatter:off
+			.selectFrom(T_LESSON)
+			.where(T_LESSON.FK_SLOT.eq(slotId));
+		// @formatter:on
+		LOGGER.trace(sql);
+		return sql.fetch().size() > 0;
+	}
 }

src/main/java/de/jottyfan/bico/modules/slot/SlotService.java

@@ -36,4 +36,8 @@ public class SlotService {
 	public SlotBean loadDeletableSlot(Integer id) {
 		return repository.getSlotIfDeletable(id);
 	}
+
+	public Boolean slotHasLesson(Integer id) {
+		return id == null ? false : repository.getHasLesson(id);
+	}
 }