映射任意資料

除了支援的 Java 類型之外 (請參閱 適用於 Java 的 DynamoDB Mapper 支援的資料類型)，您還可以使用應用程式中未直接映射至 Amazon DynamoDB 類型的類型。若要映射這些類型，您必須提供將複雜類型轉換為 DynamoDB 支援之類型的實作 (反之亦然)，並使用 @DynamoDBTypeConverted 註釋來標註複雜類型存取子方法。轉換器程式碼會在儲存或載入物件時轉換資料。它也用於使用複雜類型的所有操作。請注意，在查詢和掃描操作期間比較資料時，會針對 DynamoDB 中所存放的資料進行比較。

例如，請考慮下列可定義本身為 CatalogItem 之 Dimension 屬性的 DimensionType 類別。此屬性會將項目維度存放為高度、寬度和厚度。假設您決定將這些項目維度存放為 DynamoDB 中的字串 (例如 8.5x11x.05)。下列範例提供轉換器程式碼，以將 DimensionType 物件轉換為字串以及將字串轉換為 DimensionType。

注意

此程式碼範例假設您已根據 在 DynamoDB 中建立資料表，以及載入程式碼範例的資料 一節的說明將資料載入 DynamoDB 的帳戶。

如需執行下列範例的 step-by-step 指示，請參閱Java 程式碼範例。

範例

public class DynamoDBMapperExample {

    static AmazonDynamoDB client;

    public static void main(String[] args) throws IOException {

        // Set the AWS region you want to access.
        Regions usWest2 = Regions.US_WEST_2;
        client = AmazonDynamoDBClientBuilder.standard().withRegion(usWest2).build();

        DimensionType dimType = new DimensionType();
        dimType.setHeight("8.00");
        dimType.setLength("11.0");
        dimType.setThickness("1.0");

        Book book = new Book();
        book.setId(502);
        book.setTitle("Book 502");
        book.setISBN("555-5555555555");
        book.setBookAuthors(new HashSet<String>(Arrays.asList("Author1", "Author2")));
        book.setDimensions(dimType);

        DynamoDBMapper mapper = new DynamoDBMapper(client);
        mapper.save(book);

        Book bookRetrieved = mapper.load(Book.class, 502);
        System.out.println("Book info: " + "\n" + bookRetrieved);

        bookRetrieved.getDimensions().setHeight("9.0");
        bookRetrieved.getDimensions().setLength("12.0");
        bookRetrieved.getDimensions().setThickness("2.0");

        mapper.save(bookRetrieved);

        bookRetrieved = mapper.load(Book.class, 502);
        System.out.println("Updated book info: " + "\n" + bookRetrieved);
    }

    @DynamoDBTable(tableName = "ProductCatalog")
    public static class Book {
        private int id;
        private String title;
        private String ISBN;
        private Set<String> bookAuthors;
        private DimensionType dimensionType;

        // Partition key
        @DynamoDBHashKey(attributeName = "Id")
        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        @DynamoDBAttribute(attributeName = "Title")
        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        @DynamoDBAttribute(attributeName = "ISBN")
        public String getISBN() {
            return ISBN;
        }

        public void setISBN(String ISBN) {
            this.ISBN = ISBN;
        }

        @DynamoDBAttribute(attributeName = "Authors")
        public Set<String> getBookAuthors() {
            return bookAuthors;
        }

        public void setBookAuthors(Set<String> bookAuthors) {
            this.bookAuthors = bookAuthors;
        }

        @DynamoDBTypeConverted(converter = DimensionTypeConverter.class)
        @DynamoDBAttribute(attributeName = "Dimensions")
        public DimensionType getDimensions() {
            return dimensionType;
        }

        @DynamoDBAttribute(attributeName = "Dimensions")
        public void setDimensions(DimensionType dimensionType) {
            this.dimensionType = dimensionType;
        }

        @Override
        public String toString() {
            return "Book [ISBN=" + ISBN + ", bookAuthors=" + bookAuthors + ", dimensionType= "
                    + dimensionType.getHeight() + " X " + dimensionType.getLength() + " X "
                    + dimensionType.getThickness()
                    + ", Id=" + id + ", Title=" + title + "]";
        }
    }

    static public class DimensionType {

        private String length;
        private String height;
        private String thickness;

        public String getLength() {
            return length;
        }

        public void setLength(String length) {
            this.length = length;
        }

        public String getHeight() {
            return height;
        }

        public void setHeight(String height) {
            this.height = height;
        }

        public String getThickness() {
            return thickness;
        }

        public void setThickness(String thickness) {
            this.thickness = thickness;
        }
    }

    // Converts the complex type DimensionType to a string and vice-versa.
    static public class DimensionTypeConverter implements DynamoDBTypeConverter<String, DimensionType> {

        @Override
        public String convert(DimensionType object) {
            DimensionType itemDimensions = (DimensionType) object;
            String dimension = null;
            try {
                if (itemDimensions != null) {
                    dimension = String.format("%s x %s x %s", itemDimensions.getLength(), itemDimensions.getHeight(),
                            itemDimensions.getThickness());
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            return dimension;
        }

        @Override
        public DimensionType unconvert(String s) {

            DimensionType itemDimension = new DimensionType();
            try {
                if (s != null && s.length() != 0) {
                    String[] data = s.split("x");
                    itemDimension.setLength(data[0].trim());
                    itemDimension.setHeight(data[1].trim());
                    itemDimension.setThickness(data[2].trim());
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

            return itemDimension;
        }
    }
}