使用EnhancedDocument不含 DynamoDB 的

雖然您通常使用的執行個體EnhancedDocument來讀取和寫入文件類型 DynamoDB 項目，但它也可以獨立於 DynamoDB 使用。

您可以使EnhancedDocuments用他們的 JSON 字符串或自定義對象之間轉換為低級別映射的AttributeValues能力，如下面的例子。

    public static void conversionWithoutDynamoDbExample() {
        Address address = new Address();
        address.setCity("my city");
        address.setState("my state");
        address.setStreet("my street");
        address.setZipCode("00000");

        // Build an EnhancedDocument instance for its conversion functionality alone.
        EnhancedDocument addressEnhancedDoc = EnhancedDocument.builder()
                // Important: You must specify attribute converter providers when you build an EnhancedDocument instance not used with a DynamoDB table.
                .attributeConverterProviders(new CustomAttributeConverterProvider(), DefaultAttributeConverterProvider.create())
                .put("addressDoc", address, Address.class)
                .build();

        // Convert address to a low-level item representation.
        final Map<String, AttributeValue> addressAsAttributeMap = addressEnhancedDoc.getMapOfUnknownType("addressDoc");
        logger.info("addressAsAttributeMap: {}", addressAsAttributeMap.toString());

        // Convert address to a JSON string.
        String addressAsJsonString = addressEnhancedDoc.getJson("addressDoc");
        logger.info("addressAsJsonString: {}", addressAsJsonString);
        // Convert addressEnhancedDoc back to an Address instance.
        Address addressConverted =  addressEnhancedDoc.get("addressDoc", Address.class);
        logger.info("addressConverted: {}", addressConverted.toString());
    }

   /* Console output:
          addressAsAttributeMap: {zipCode=AttributeValue(S=00000), state=AttributeValue(S=my state), street=AttributeValue(S=my street), city=AttributeValue(S=my city)}
          addressAsJsonString: {"zipCode":"00000","state":"my state","street":"my street","city":"my city"}
          addressConverted: Address{street='my street', city='my city', state='my state', zipCode='00000'}
   */ 

注意

當您使用獨立於 DynamoDB 表格的增強型文件時，請務必在建構器上明確設定屬性轉換器提供者。

相反地，當增強型文件搭配 DynamoDB 表使用時，文件表格結構描述會提供轉換器提供者。