add dto, refactor names, update controllers

src/main/java/com/faf223/expensetrackerfaf/dto/mappers/ExpenseMapper.java

@@ -0,0 +1,31 @@
+package com.faf223.expensetrackerfaf.dto.mappers;
+
+import com.faf223.expensetrackerfaf.dto.ExpenseCreationDTO;
+import com.faf223.expensetrackerfaf.dto.ExpenseDTO;
+import com.faf223.expensetrackerfaf.model.Expense;
+import com.faf223.expensetrackerfaf.service.ExpenseService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExpenseMapper {
+
+    private final ExpenseService expenseService;
+    private final UserMapper userMapper;
+
+    @Autowired
+    public ExpenseMapper(ExpenseService expenseService, UserMapper userMapper) {
+        this.expenseService = expenseService;
+        this.userMapper = userMapper;
+    }
+
+    public ExpenseDTO toDto(Expense expense) {
+        return new ExpenseDTO(expense.getExpenseId(), userMapper.toDto(expense.getUser()),
+                expense.getCategory(), expense.getDate(), expense.getAmount());
+    }
+
+    public Expense toExpense(ExpenseCreationDTO expenseDTO) {
+        return expenseService.getExpenseById(expenseDTO.getExpenseId());
+    }
+
+}