Wrote OfferWriter and following classes to save offers to persistence

src/main/java/de/rwu/easydrop/service/mapping/OfferMapper.java

@@ -0,0 +1,50 @@
+package de.rwu.easydrop.service.mapping;
+
+import de.rwu.easydrop.api.dto.OfferDTO;
+
+import de.rwu.easydrop.model.Offer;
+
+/**
+ * Maps between Offer, OfferDTO and OfferDTO.
+ *
+ * @since 0.2.0
+ *
+ * @see Offer
+ * @see OfferDTO
+ * @see OfferDTO
+ */
+public final class OfferMapper {
+
+    /**
+     * Private constructor to prevent unwanted instantiation.
+     *
+     * @throws UnsupportedOperationException always
+     */
+    private OfferMapper() throws UnsupportedOperationException {
+        throw new UnsupportedOperationException("This is a mapping class, don't instantiate it.");
+    }
+
+    /**
+     * Creates a Offer object from a corresponding DTO.
+     *
+     * @param dto Offer Data Transfer Object
+     * @return Offer
+     */
+    public static Offer mapOfferFromDTO(final OfferDTO dto) {
+        Offer offer = new Offer();
+
+        return offer;
+    }
+
+    /**
+     * Creates an OfferDTO object from a corresponding offer.
+     *
+     * @param Offer offer
+     * @return OfferDTO
+     */
+    public static OfferDTO mapOfferToDTO(final Offer offer) {
+        OfferDTO dto = new OfferDTO(offer.getOfferId());
+
+        return dto;
+    }
+}

src/main/java/de/rwu/easydrop/service/validation/OfferValidator.java

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+package de.rwu.easydrop.service.validation;
+import java.util.HashSet;
+import java.util.Set;
+
+import de.rwu.easydrop.exception.InvalidProductException;
+import de.rwu.easydrop.model.Product;
+import de.rwu.easydrop.model.Offer;
+
+/**
+ * Confirms validity of Offer data.
+ *
+ * @since 0.2.0
+ */
+public class OfferValidator {
+        /**
+     * Private constructor to prevent unwanted instantiation.
+     *
+     * @throws UnsupportedOperationException always
+     */
+    private OfferValidator() throws UnsupportedOperationException {
+        throw new UnsupportedOperationException("This is a validator class, don't instantiate it.");
+    }
+        /**
+     * Makes sure an Offer does not contain invalid information.
+     *
+     * @param offer the Offer
+     */
+    public static void validate(final Offer offer) {}
+}
+
+
+

src/main/java/de/rwu/easydrop/service/writer/OfferWriter.java

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+package de.rwu.easydrop.service.writer;
+
+import de.rwu.easydrop.api.dto.OfferDTO;
+import de.rwu.easydrop.data.connector.AbstractOfferPersistence;
+import de.rwu.easydrop.model.Offer;
+import de.rwu.easydrop.service.mapping.OfferMapper;
+import de.rwu.easydrop.service.validation.OfferValidator;
+
+public class OfferWriter {
+    /**
+     * Persistence.
+     */
+    private AbstractOfferPersistence persistence;
+
+    /**
+     * @param newPersistence the persistence to set
+     */
+    public void setPersistence(final AbstractOfferPersistence newPersistence) {
+        this.persistence = newPersistence;
+    }
+
+    /**
+     * Validates and saves product to persistence.
+     *
+     * @param product
+     */
+    public void writeOfferToPersistence(final Offer offer) {
+        OfferValidator.validate(offer);
+        OfferDTO dto = OfferMapper.mapOfferToDTO(offer);
+
+        persistence.saveOffer(dto);
+    }
+}