Add sources for BAEL-468 (#4171)

* Added POJO,
* Added DTO,
* Added Mapper

mapstruct/src/main/java/com/baeldung/dto/TransactionDTO.java

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+package com.baeldung.dto;
+
+public class TransactionDTO {
+
+    private String uuid;
+    private Long totalInCents;
+
+    public String getUuid() {
+        return uuid;
+    }
+
+    public void setUuid(String uuid) {
+        this.uuid = uuid;
+    }
+
+    public Long getTotalInCents() {
+        return totalInCents;
+    }
+
+    public void setTotalInCents(Long totalInCents) {
+        this.totalInCents = totalInCents;
+    }
+}

mapstruct/src/main/java/com/baeldung/entity/Transaction.java

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+package com.baeldung.entity;
+
+import java.math.BigDecimal;
+import java.util.UUID;
+
+public class Transaction {
+
+    private Long id;
+    private String uuid = UUID.randomUUID().toString();
+    private BigDecimal total;
+
+    public Long getId() {
+        return id;
+    }
+
+    public String getUuid() {
+        return uuid;
+    }
+
+    public BigDecimal getTotal() {
+        return total;
+    }
+}

mapstruct/src/main/java/com/baeldung/mapper/TransactionMapper.java

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+package com.baeldung.mapper;
+
+import java.math.BigDecimal;
+import java.util.Collection;
+import java.util.List;
+
+import org.mapstruct.Mapper;
+
+import com.baeldung.dto.TransactionDTO;
+import com.baeldung.entity.Transaction;
+
+@Mapper
+abstract class TransactionMapper {
+
+    public TransactionDTO toTransactionDTO(Transaction transaction) {
+        TransactionDTO transactionDTO = new TransactionDTO();
+        transactionDTO.setUuid(transaction.getUuid());
+        transactionDTO.setTotalInCents(transaction.getTotal().multiply(new BigDecimal("100")).longValue());
+        return transactionDTO;
+    }
+
+    public abstract List<TransactionDTO> toTransactionDTO(Collection<Transaction> transactions);
+}