下一个需求不像想象中那么简单，当用户投4个0.25元和1元，购买1美元的零食，我们应该接受哪种面额的货币？这种情况是没有料想到的，这时可以和领域专家讨论。在这里，售货机有限接收低面值的货币，返回高面值的1元。

    1. package com.lugew.springbootddd.snackmachine;
    3. import com.lugew.springbootddd.ValueObject;
    4. import lombok.Getter;
    6. /**
    7.  * @author 夏露桂
    8.  * @since 2021/6/7 11:59
    9.  */
    10. @Getter
    11. public class Money extends ValueObject<Money> {
    13.     public static Money None = new Money(0, 0, 0, 0, 0, 0);
    14.     public static Money Cent = new Money(1, 0, 0, 0, 0, 0);
    15.     public static Money TenCent = new Money(0, 1, 0, 0, 0, 0);
    16.     public static Money Quarter = new Money(0, 0, 1, 0, 0, 0);
    17.     public static Money Dollar = new Money(0, 0, 0, 1, 0, 0);
    18.     public static Money FiveDollar = new Money(0, 0, 0, 0, 1, 0);
    19.     public static Money TwentyDollar = new Money(0, 0, 0, 0, 0, 1);
    21.     private final int oneCentCount;
    22.     private final int tenCentCount;
    23.     private final int quarterCount;
    24.     private final int oneDollarCount;
    25.     private final int fiveDollarCount;
    26.     private final int twentyDollarCount;
    27.     private float amount;
    29.     public float getAmount() {
    30.         return oneCentCount * 0.01f + tenCentCount * 0.10f + quarterCount * 0.25f +
    31.                 oneDollarCount * 1f
    32.                 + fiveDollarCount * 5f + twentyDollarCount * 20f;
    33.     }
    35.     public Money(int oneCentCount, int tenCentCount, int quarterCount, int
    36.             oneDollarCount, int fiveDollarCount, int twentyDollarCount) {
    37.         if (oneCentCount < 0)
    38.             throw new IllegalStateException();
    39.         if (tenCentCount < 0)
    40.             throw new IllegalStateException();
    41.         if (quarterCount < 0)
    42.             throw new IllegalStateException();
    43.         if (oneDollarCount < 0)
    44.             throw new IllegalStateException();
    45.         if (fiveDollarCount < 0)
    46.             throw new IllegalStateException();
    47.         if (twentyDollarCount < 0)
    48.             throw new IllegalStateException();
    50.         this.oneCentCount = oneCentCount;
    51.         this.tenCentCount = tenCentCount;
    52.         this.quarterCount = quarterCount;
    53.         this.oneDollarCount = oneDollarCount;
    54.         this.fiveDollarCount = fiveDollarCount;
    55.         this.twentyDollarCount = twentyDollarCount;
    56.     }
    58.     public Money(float amount, int oneCentCount, int tenCentCount, int quarterCount, int
    59.             oneDollarCount, int fiveDollarCount, int twentyDollarCount) {
    60.         this(oneCentCount, tenCentCount, quarterCount, oneDollarCount, fiveDollarCount, twentyDollarCount);
    61.         if (amount < 0) {
    62.             throw new IllegalStateException();
    63.         }
    64.         this.amount = amount;
    65.     }
    67.     public Money substract(Money other) {
    68.         return new Money(
    69.                 oneCentCount - other.oneCentCount,
    70.                 tenCentCount - other.tenCentCount,
    71.                 quarterCount - other.quarterCount,
    72.                 oneDollarCount - other.oneDollarCount,
    73.                 fiveDollarCount - other.fiveDollarCount,
    74.                 twentyDollarCount - other.twentyDollarCount);
    75.     }
    77.     public static Money add(Money money1, Money money2) {
    79.         return new Money(
    80.                 money1.oneCentCount + money2.oneCentCount,
    81.                 money1.tenCentCount + money2.tenCentCount,
    82.                 money1.quarterCount + money2.quarterCount,
    83.                 money1.oneDollarCount + money2.oneDollarCount,
    84.                 money1.fiveDollarCount + money2.fiveDollarCount,
    85.                 money1.twentyDollarCount + money2.twentyDollarCount);
    86.     }
    88.     public Money add(Money other) {
    89.         return new Money(
    90.                 other.oneCentCount + this.oneCentCount,
    91.                 other.tenCentCount + this.tenCentCount,
    92.                 other.quarterCount + this.quarterCount,
    93.                 other.oneDollarCount + this.oneDollarCount,
    94.                 other.fiveDollarCount + this.fiveDollarCount,
    95.                 other.twentyDollarCount + this.twentyDollarCount);
    96.     }
    98.     @Override
    99.     protected boolean equalsCore(Money other) {
    100.         return oneCentCount == other.oneCentCount
    101.                 && tenCentCount == other.tenCentCount
    102.                 && quarterCount == other.quarterCount
    103.                 && oneDollarCount == other.oneDollarCount
    104.                 && fiveDollarCount == other.fiveDollarCount
    105.                 && twentyDollarCount == other.twentyDollarCount;
    106.     }
    108.     @Override
    109.     protected int getHashCodeCore() {
    110.         int hashCode = oneCentCount;
    111.         hashCode = (hashCode * 397) ^ tenCentCount;
    112.         hashCode = (hashCode * 397) ^ quarterCount;
    113.         hashCode = (hashCode * 397) ^ oneDollarCount;
    114.         hashCode = (hashCode * 397) ^ fiveDollarCount;
    115.         hashCode = (hashCode * 397) ^ twentyDollarCount;
    116.         return hashCode;
    117.     }
    119.     @Override
    120.     public String toString() {
    121.         if (getAmount() < 1)
    122.             return "¢" + getAmount() * 100;
    123.         return "$" + getAmount();
    124.     }
    125. }
    1. package com.lugew.springbootddd.snackmachine;
    3. import com.lugew.springbootddd.AggregateRoot;
    4. import com.lugew.springbootddd.Slot;
    5. import com.lugew.springbootddd.SnackMachineDto;
    6. import com.lugew.springbootddd.SnackPile;
    7. import lombok.Getter;
    8. import lombok.Setter;
    10. import java.util.ArrayList;
    11. import java.util.Arrays;
    12. import java.util.List;
    14. import static com.lugew.springbootddd.snackmachine.Money.None;
    17. public final class SnackMachine extends AggregateRoot {
    19.     @Getter
    20.     @Setter
    21.     private Money moneyInside;
    24.     @Getter
    25.     @Setter
    26.     private float moneyInTransaction;
    27.     private List<Slot> slots;
    29.     public SnackMachine() {
    30.         moneyInside = None;
    31.         moneyInTransaction = 0;
    32.         slots = new ArrayList<>();
    33.         slots.add(new Slot(this, 1));
    34.         slots.add(new Slot(this, 2));
    35.         slots.add(new Slot(this, 3));
    36.     }
    38.     public Slot getSlot(int position) {
    39.         return slots.stream().filter(x -> x.getPosition() ==
    40.                 position).findAny().orElse(null);
    41.     }
    43.     public SnackPile getSnackPile(int position) {
    44.         return getSlot(position).getSnackPile();
    45.     }
    47.     public void insertMoney(Money money) {
    48.         Money[] coinsAndNotes = {Money.Cent, Money.TenCent, Money.Quarter,
    49.                 Money.Dollar, Money.FiveDollar,
    50.                 Money.TwentyDollar};
    51.         if (!Arrays.asList(coinsAndNotes).contains(money))
    52.             throw new IllegalStateException();
    53.         moneyInTransaction = moneyInTransaction + money.getAmount();
    54.         moneyInside = moneyInside.add(money);
    55.     }
    57.     public void returnMoney() {
    58.         moneyInTransaction = 0;
    59.     }
    61.     public void buySnack(int position) {
    62.         Slot slot = getSlot(position);
    63.         if (slot.getSnackPile().getPrice() > moneyInTransaction) {
    64.             throw new IllegalStateException();
    65.         }
    66.         slot.setSnackPile(slot.getSnackPile().subtractOne());
    67.         moneyInTransaction = 0;
    68.     }
    70.     public SnackMachineDto convertToSnackMachineDto() {
    71.         SnackMachineDto snackMachineDto = new SnackMachineDto();
    72.         snackMachineDto.setId(id);
    73.         snackMachineDto.setMoneyInTransaction(moneyInTransaction);
    74.         snackMachineDto.setOneCentCount(moneyInside.getOneCentCount());
    75.         snackMachineDto.setTenCentCount(moneyInside.getTenCentCount());
    76.         snackMachineDto.setQuarterCount(moneyInside.getQuarterCount());
    77.         snackMachineDto.setOneDollarCount(moneyInside.getOneDollarCount());
    78.         snackMachineDto.setFiveDollarCount(moneyInside.getFiveDollarCount());
    79.         snackMachineDto.setTwentyDollarCount(moneyInside.getTwentyDollarCount());
    80.         return snackMachineDto;
    81.     }
    83.     public void loadSnacks(int position, SnackPile snackPile) {
    84.         Slot slot = slots.stream().filter(x -> x.getPosition() ==
    85.                 position).findAny().orElse(null);
    86.         if (slot != null) {
    87.             slot.setSnackPile(snackPile);
    88.         }
    89.     }
    92. }
    1. package com.lugew.springbootddd;
    3. import com.lugew.springbootddd.snackmachine.SnackMachine;
    4. import lombok.RequiredArgsConstructor;
    5. import org.springframework.web.bind.annotation.*;
    7. import static com.lugew.springbootddd.snackmachine.Money.*;
    9. /**
    10.  * @author 夏露桂
    11.  * @since 2021/6/10 11:55
    12.  */
    13. @RestController
    14. @RequestMapping("snackmachines")
    15. @RequiredArgsConstructor
    16. public class SnackMachineController {
    17.     private final SnackMachineRepository snackMachineRepository;
    19.     @GetMapping("/{id}")
    20.     @ResponseBody
    21.     public SnackMachineDto getSnackMachine(@PathVariable("id") long id) {
    22.         return snackMachineRepository.findById(id).orElse(null);
    23.     }
    25.     @PutMapping("/{id}/{slotNumber}")
    26.     public void buySnack(@PathVariable("id") long id, @PathVariable("slotNumber")
    27.             int slotNumber) {
    28.         SnackMachineDto snackMachineDto =
    29.                 snackMachineRepository.findById(id).orElse(null);
    30.         SnackMachine snackMachine = snackMachineDto.convertToSnackMachine();
    31.         snackMachine.buySnack(slotNumber);
    32.         snackMachineRepository.save(snackMachine.convertToSnackMachineDto());
    33.     }
    35.     @PutMapping("/{id}/moneyInTransaction/{coinOrNote}")
    36.     public void insertCoinOrNote(@PathVariable("id") long id, @PathVariable("coinOrNote") String coinOrNote) {
    37.         SnackMachineDto snackMachineDto =
    38.                 snackMachineRepository.findById(id).orElse(null);
    39.         SnackMachine snackMachine = snackMachineDto.convertToSnackMachine();
    40.         if (coinOrNote.equalsIgnoreCase("Cent")) snackMachine.insertMoney(Cent);
    41.         else if (coinOrNote.equalsIgnoreCase("TenCent"))
    42.             snackMachine.insertMoney(TenCent);
    43.         else if (coinOrNote.equalsIgnoreCase("Quarter"))
    44.             snackMachine.insertMoney(Quarter);
    45.         else if (coinOrNote.equalsIgnoreCase("Dollar"))
    46.             snackMachine.insertMoney(Dollar);
    47.         else if (coinOrNote.equalsIgnoreCase("FiveDollar"))
    48.             snackMachine.insertMoney(FiveDollar);
    49.         else if (coinOrNote.equalsIgnoreCase("TwentyDollar"))
    50.             snackMachine.insertMoney(TwentyDollar);
    51.         snackMachineRepository.save(snackMachine.convertToSnackMachineDto());
    52.     }
    54.     @PutMapping("/{id}/moneyInTransaction")
    55.     public void returnMoney(@PathVariable("id") long id) {
    56.         SnackMachineDto snackMachineDto =
    57.                 snackMachineRepository.findById(id).orElse(null);
    58.         SnackMachine snackMachine = snackMachineDto.convertToSnackMachine();
    59.         snackMachine.returnMoney();
    60.         snackMachineRepository.save(snackMachine.convertToSnackMachineDto());
    61.     }
    63. /*    public Money getWholeMoney(SnackMachine snackMachine) {
    64.         return Money.add(snackMachine.getMoneyInside(), snackMachine.getMoneyInTransaction());
    65.     }*/
    67. }
    1. package com.lugew.springbootddd;
    3. import com.lugew.springbootddd.snackmachine.Money;
    4. import com.lugew.springbootddd.snackmachine.SnackMachine;
    5. import lombok.Getter;
    6. import lombok.Setter;
    8. import javax.persistence.Entity;
    9. import javax.persistence.GeneratedValue;
    10. import javax.persistence.Id;
    12. /**
    13.  * @author 夏露桂
    14.  * @since 2021/6/10 12:00
    15.  */
    16. @Getter
    17. @Setter
    18. @Entity
    19. public class SnackMachineDto {
    20.     @Id
    21.     @GeneratedValue
    22.     private long id;
    23.     private int oneCentCount;
    24.     private int tenCentCount;
    25.     private int quarterCount;
    26.     private int oneDollarCount;
    27.     private int fiveDollarCount;
    28.     private int twentyDollarCount;
    29.     private float moneyInTransaction;
    31.     public SnackMachine convertToSnackMachine() {
    32.         SnackMachine snackMachine = new SnackMachine();
    33.         snackMachine.setId(id);
    34.         snackMachine.setMoneyInTransaction(moneyInTransaction);
    35.         snackMachine.setMoneyInside(new
    36.                 Money(oneCentCount, tenCentCount, quarterCount, oneDollarCount, fiveDollarCount, twentyDollarCount));
    37.         return snackMachine;
    38.     }
    39. }
    1. package com.lugew.springbootddd.snackmachine;
    3. import com.lugew.springbootddd.Snack;
    4. import com.lugew.springbootddd.SnackPile;
    5. import org.junit.jupiter.api.Test;
    7. import static com.lugew.springbootddd.snackmachine.Money.Cent;
    8. import static com.lugew.springbootddd.snackmachine.Money.Dollar;
    9. import static org.junit.jupiter.api.Assertions.assertEquals;
    10. import static org.junit.jupiter.api.Assertions.assertThrows;
    12. /**
    13.  * @author 夏露桂
    14.  * @since 2021/6/9 18:12
    15.  */
    16. public class SnackMachineTest {
    18.     @Test
    19.     public void return_money_empties_money_in_transaction() {
    20.         SnackMachine snackMachine = new SnackMachine();
    21.         snackMachine.insertMoney(Dollar);
    22.         snackMachine.returnMoney();
    23.         assertEquals(snackMachine.getMoneyInTransaction(), 0, 0);
    24.     }
    26.     @Test
    27.     public void inserted_money_goes_to_money_in_transaction() {
    28.         SnackMachine snackMachine = new SnackMachine();
    29.         snackMachine.insertMoney(Cent);
    30.         snackMachine.insertMoney(Dollar);
    31.         assertEquals(snackMachine.getMoneyInTransaction(), 1.01f, 0);
    32.     }
    34.     @Test
    35.     public void cannot_insert_more_than_one_coin_or_note_at_a_time() {
    36.         SnackMachine snackMachine = new SnackMachine();
    37.         Money twoCent = Money.add(Cent, Cent);
    38.         assertThrows(IllegalStateException.class, () -> {
    39.             snackMachine.insertMoney(twoCent);
    40.         });
    41.     }
    43.     @Test
    44.     public void buySnack_trades_inserted_money_for_a_snack() {
    46.         SnackMachine snackMachine = new SnackMachine();
    48.         snackMachine.loadSnacks(1, new SnackPile(new Snack("Some snack"), 10, 1));
    49.         snackMachine.insertMoney(Dollar);
    50.         snackMachine.buySnack(1);
    51.         assertEquals(snackMachine.getMoneyInTransaction(), Money.None.getAmount());
    52.         assertEquals(snackMachine.getMoneyInside().getAmount(), 1, 0.5);
    53.         assertEquals(snackMachine.getSnackPile(1).getQuantity(), 9);
    54.     }
    56.     @Test
    57.     public void cannot_make_purchase_when_there_is_no_snacks() {
    58.         SnackMachine snackMachine = new SnackMachine();
    59.         assertThrows(IllegalStateException.class, () -> {
    60.             snackMachine.buySnack(1);
    61.         });
    62.     }
    64.     @Test
    65.     public void cannot_make_purchase_if_not_enough_money_inserted() {
    66.         SnackMachine snackMachine = new SnackMachine();
    67.         snackMachine.loadSnacks(1, new SnackPile(new Snack("Some snack"), 1, 2));
    68.         snackMachine.insertMoney(Dollar);
    69.         assertThrows(IllegalStateException.class, () -> {
    70.             snackMachine.buySnack(1);
    71.         });
    73.     }
    75. /*    @Test
    76.     public void snack_machine_returns_money_with_highest_denomination_first() {
    77.         SnackMachine snackMachine = new SnackMachine();
    78.         snackMachine.loadMoney(Dollar);
    79.         snackMachine.insertMoney(Quarter);
    80.         snackMachine.insertMoney(Quarter);
    81.         snackMachine.insertMoney(Quarter);
    82.         snackMachine.insertMoney(Quarter);
    83.         snackMachine.returnMoney();
    84.         assertEquals(snackMachine.getMoneyInside().getQuarterCount(), 4);
    85.         assertEquals(snackMachine.getMoneyInside().getOneDollarCount(), 0);
    86.     }*/
    87. }

    我们将moneyInTransaction重构为float类型，因为moneyInTransaction和找零的数额可能是不同的（找零优先高面额）。在此重构了和此字段有关的所有类。还需要重构Controller和SnackMachine：

    1. package com.lugew.springbootddd;
    3. import com.lugew.springbootddd.snackmachine.SnackMachine;
    4. import lombok.RequiredArgsConstructor;
    5. import org.springframework.web.bind.annotation.*;
    7. import static com.lugew.springbootddd.snackmachine.Money.*;
    9. /**
    10.  * @author 夏露桂
    11.  * @since 2021/6/10 11:55
    12.  */
    13. @RestController
    14. @RequestMapping("snackmachines")
    15. @RequiredArgsConstructor
    16. public class SnackMachineController {
    17.     private final SnackMachineRepository snackMachineRepository;
    19.     @GetMapping("/{id}")
    20.     @ResponseBody
    21.     public SnackMachineDto getSnackMachine(@PathVariable("id") long id) {
    22.         return snackMachineRepository.findById(id).orElse(null);
    23.     }
    25.     @PutMapping("/{id}/moneyInTransaction/{coinOrNote}")
    26.     public void insertCoinOrNote(@PathVariable("id") long id, @PathVariable("coinOrNote") String coinOrNote) {
    27.         SnackMachineDto snackMachineDto =
    28.                 snackMachineRepository.findById(id).orElse(null);
    29.         SnackMachine snackMachine = snackMachineDto.convertToSnackMachine();
    30.         if (coinOrNote.equalsIgnoreCase("Cent")) snackMachine.insertMoney(Cent);
    31.         else if (coinOrNote.equalsIgnoreCase("TenCent"))
    32.             snackMachine.insertMoney(TenCent);
    33.         else if (coinOrNote.equalsIgnoreCase("Quarter"))
    34.             snackMachine.insertMoney(Quarter);
    35.         else if (coinOrNote.equalsIgnoreCase("Dollar"))
    36.             snackMachine.insertMoney(Dollar);
    37.         else if (coinOrNote.equalsIgnoreCase("FiveDollar"))
    38.             snackMachine.insertMoney(FiveDollar);
    39.         else if (coinOrNote.equalsIgnoreCase("TwentyDollar"))
    40.             snackMachine.insertMoney(TwentyDollar);
    41.         snackMachineRepository.save(snackMachine.convertToSnackMachineDto());
    42.     }
    44.     @PutMapping("/{id}/moneyInTransaction")
    45.     public void returnMoney(@PathVariable("id") long id) {
    46.         SnackMachineDto snackMachineDto =
    47.                 snackMachineRepository.findById(id).orElse(null);
    48.         SnackMachine snackMachine = snackMachineDto.convertToSnackMachine();
    49.         snackMachine.returnMoney();
    50.         snackMachineRepository.save(snackMachine.convertToSnackMachineDto());
    51.     }
    54.     @PutMapping("/{id}/{slotNumber}")
    55.     public void buySnack(@PathVariable("id") long id, @PathVariable("slotNumber")
    56.             int slotNumber) {
    57.         SnackMachineDto snackMachineDto =
    58.                 snackMachineRepository.findById(id).orElse(null);
    59.         SnackMachine snackMachine = snackMachineDto.convertToSnackMachine();
    60.         snackMachine.buySnack(slotNumber);
    61.         snackMachineRepository.save(snackMachine.convertToSnackMachineDto());
    62.     }
    64. }
    1. package com.lugew.springbootddd.snackmachine;
    3. import com.lugew.springbootddd.*;
    4. import lombok.Getter;
    5. import lombok.Setter;
    7. import java.util.ArrayList;
    8. import java.util.Arrays;
    9. import java.util.List;
    11. import static com.lugew.springbootddd.snackmachine.Money.None;
    14. public final class SnackMachine extends AggregateRoot {
    16.     @Getter
    17.     @Setter
    18.     private Money moneyInside;
    21.     @Getter
    22.     @Setter
    23.     private float moneyInTransaction;
    24.     @Setter
    25.     private List<Slot> slots;
    27.     public SnackMachine() {
    28.         moneyInside = None;
    29.         moneyInTransaction = 0;
    30.         slots = new ArrayList<>();
    31.         slots.add(new Slot(this, 1));
    32.         slots.add(new Slot(this, 2));
    33.         slots.add(new Slot(this, 3));
    34.     }
    36.     public Slot getSlot(int position) {
    37.         return slots.stream().filter(x -> x.getPosition() ==
    38.                 position).findAny().orElse(null);
    39.     }
    41.     public SnackPile getSnackPile(int position) {
    42.         return getSlot(position).getSnackPile();
    43.     }
    45.     public void insertMoney(Money money) {
    46.         Money[] coinsAndNotes = {Money.Cent, Money.TenCent, Money.Quarter,
    47.                 Money.Dollar, Money.FiveDollar,
    48.                 Money.TwentyDollar};
    49.         if (!Arrays.asList(coinsAndNotes).contains(money))
    50.             throw new IllegalStateException();
    51.         moneyInTransaction = moneyInTransaction + money.getAmount();
    52.         moneyInside = moneyInside.add(money);
    53.     }
    55.     public void returnMoney() {
    56.         moneyInTransaction = 0;
    57.     }
    59.     public void buySnack(int position) {
    60.         Slot slot = getSlot(position);
    61.         if (slot.getSnackPile().getPrice() > moneyInTransaction) {
    62.             throw new IllegalStateException();
    63.         }
    64.         slot.setSnackPile(slot.getSnackPile().subtractOne());
    65.         moneyInTransaction = 0;
    66.     }
    68.     public SnackMachineDto convertToSnackMachineDto() {
    69.         SnackMachineDto snackMachineDto = new SnackMachineDto();
    70.         snackMachineDto.setId(id);
    71.         snackMachineDto.setMoneyInTransaction(moneyInTransaction);
    72.         List<SlotDto> slotDtoList = new ArrayList<>();
    73.         for (Slot slot : slots) slotDtoList.add(slot.convertToSlotDto());
    74.         snackMachineDto.setSlotDtoList(slotDtoList);
    75.         snackMachineDto.setOneCentCount(moneyInside.getOneCentCount());
    76.         snackMachineDto.setTenCentCount(moneyInside.getTenCentCount());
    77.         snackMachineDto.setQuarterCount(moneyInside.getQuarterCount());
    78.         snackMachineDto.setOneDollarCount(moneyInside.getOneDollarCount());
    79.         snackMachineDto.setFiveDollarCount(moneyInside.getFiveDollarCount());
    80.         snackMachineDto.setTwentyDollarCount(moneyInside.getTwentyDollarCount());
    81.         return snackMachineDto;
    82.     }
    84.     public void loadSnacks(int position, SnackPile snackPile) {
    85.         Slot slot = slots.stream().filter(x -> x.getPosition() ==
    86.                 position).findAny().orElse(null);
    87.         if (slot != null) {
    88.             slot.setSnackPile(snackPile);
    89.         }
    90.     }
    93.     public void loadMoney(Money money) {
    94.         moneyInside = moneyInside.add(money);
    95.     }
    96. }
    1. package com.lugew.springbootddd;
    3. import com.lugew.springbootddd.snackmachine.Money;
    4. import com.lugew.springbootddd.snackmachine.SnackMachine;
    5. import lombok.Getter;
    6. import lombok.Setter;
    8. import javax.persistence.Entity;
    9. import javax.persistence.*;
    10. import java.util.ArrayList;
    11. import java.util.List;
    13. /**
    14.  * @author 夏露桂
    15.  * @since 2021/6/10 12:00
    16.  */
    17. @Getter
    18. @Setter
    19. @Entity
    20. public class SnackMachineDto {
    21.     @Id
    22.     @GeneratedValue
    23.     private long id;
    24.     private int oneCentCount;
    25.     private int tenCentCount;
    26.     private int quarterCount;
    27.     private int oneDollarCount;
    28.     private int fiveDollarCount;
    29.     private int twentyDollarCount;
    30.     private float moneyInTransaction;
    31.     @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    32.     @JoinColumn(name = "snackMachineId")
    33.     private List<SlotDto> slotDtoList;
    35.     public SnackMachine convertToSnackMachine() {
    36.         SnackMachine snackMachine = new SnackMachine();
    37.         snackMachine.setId(id);
    38.         snackMachine.setMoneyInTransaction(moneyInTransaction);
    39.         snackMachine.setMoneyInside(new
    40.                 Money(oneCentCount, tenCentCount, quarterCount,
    41.                 oneDollarCount, fiveDollarCount, twentyDollarCount));
    42.         List<Slot> slotList = new ArrayList<>();
    43.         for (SlotDto slotDto : slotDtoList) {
    44.             slotList.add(slotDto.convertToSlot());
    45.         }
    46.         snackMachine.setSlots(slotList);
    47.         return snackMachine;
    48.     }
    50. }
    1.     @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    2.     @JoinColumn(name = "snackMachineId")
    3.     private List<SlotDto> slotDtoList;

    一对多关系会改变数据库，Springboot已帮我们实现。

    1.     @Test
    2.     public void snack_machine_returns_money_with_highest_denomination_first() {
    3.         SnackMachine snackMachine = new SnackMachine();
    4.         snackMachine.loadMoney(Dollar);
    5.         snackMachine.insertMoney(Quarter);
    6.         snackMachine.insertMoney(Quarter);
    7.         snackMachine.insertMoney(Quarter);
    8.         snackMachine.insertMoney(Quarter);
    9.         snackMachine.returnMoney();
    10.         assertEquals(snackMachine.getMoneyInside().getQuarterCount(), 4);
    11.         assertEquals(snackMachine.getMoneyInside().getOneDollarCount(), 0);
    12.     }

    显然测试是失败的：
    image.png
    这是我们需要重构returnMoney方法。我们给Money类引入allocate累加方法：

    1.     public void returnMoney() {
    2.         Money moneyToReturn = moneyInside.allocate(moneyInTransaction);
    3.         moneyInside = moneyInside.substract(moneyToReturn);
    4.         moneyInTransaction = 0;
    5.     }
    1.      public boolean canAllocate(float amount) {
    2.         Money money = allocateCore(amount);
    3.         return money.amount == amount;
    4.     }
    6.     public Money allocate(float amount) {
    7.         if (!canAllocate(amount))
    8.             throw new IllegalStateException();
    9.         return allocateCore(amount);
    10.     }
    12.     private Money allocateCore(float amount) {
    13.         int twentyDollarCount = Math.min((int) (amount / 20), this.twentyDollarCount);
    14.         amount = amount - twentyDollarCount * 20;
    15.         int fiveDollarCount = Math.min((int) (amount / 5), this.fiveDollarCount);
    16.         amount = amount - fiveDollarCount * 5;
    17.         int oneDollarCount = Math.min((int) amount, this.oneDollarCount);
    18.         amount = amount - oneDollarCount;
    19.         int quarterCount = Math.min((int) (amount / 0.25f), this.quarterCount);
    20.         amount = amount - quarterCount * 0.25f;
    21.         int tenCentCount = Math.min((int) (amount / 0.1f), this.tenCentCount);
    22.         amount = amount - tenCentCount * 0.1f;
    23.         int oneCentCount = Math.min((int) (amount / 0.01f), this.oneCentCount);
    24.         return new Money(
    25.                 oneCentCount,
    26.                 tenCentCount,
    27.                 quarterCount,
    28.                 oneDollarCount,
    29.                 fiveDollarCount,
    30.                 twentyDollarCount
    31.         );
    32.     }

    另一个是找零功能：

    1.     @Test
    2.     public void after_purchase_change_is_returned() {
    3.         SnackMachine snackMachine = new SnackMachine();
    4.         snackMachine.loadSnacks(1, new SnackPile(new Snack("Some snack"), 1,
    5.                 0.5f));
    6.         snackMachine.loadMoney(
    7.                 new Money(0, 10, 0, 0, 0, 0)
    8.         );
    10.         snackMachine.insertMoney(Dollar);
    11.         snackMachine.buySnack(1);
    12.         assertEquals(snackMachine.getMoneyInside().getAmount(), 1.5, 0);
    13.         assertEquals(snackMachine.getMoneyInTransaction(), 0, 0);
    14.     }

    image.png
    最后是无法找零禁止购买：

    1.     @Test
    2.     public void cannot_buy_snack_if_not_enough_change() {
    3.         SnackMachine snackMachine = new SnackMachine();
    4.         snackMachine.loadSnacks(1, new SnackPile(new Snack("Some snack"), 1, 0.5f));
    5.         snackMachine.insertMoney(Dollar);
    6.         assertThrows(IllegalStateException.class, () -> {
    7.             snackMachine.buySnack(1);
    8.         });
    9.     }

    image.png