Package software.amazon.awssdk.enhanced.dynamodb.document

Class DocumentTableSchema

  • All Implemented Interfaces:
    TableSchema<EnhancedDocument>
    public final class DocumentTableSchema
extends Object
implements TableSchema<EnhancedDocument>
    Implementation of TableSchema that builds a table schema based on DynamoDB Items.

    In Amazon DynamoDB, an item is a collection of attributes. Each attribute has a name and a value. An attribute value can be a scalar, a set, or a document type

    A DocumentTableSchema is used to create a DynamoDbTable which provides read and writes access to DynamoDB table as EnhancedDocument.

    DocumentTableSchema specifying primaryKey, sortKey and a customAttributeConverter can be created as below

    DocumentTableSchema can also be created without specifying primaryKey and sortKey in which cases the TableMetadata of DocumentTableSchema will error if we try to access attributes from metaData. Also if attributeConverterProviders are not provided then DefaultAttributeConverterProvider will be used

    See Also:
    Working with items and attributes

    • Method Detail

      • mapToItem

        public EnhancedDocument mapToItem​(Map<String,​AttributeValue> attributeMap)
        Description copied from interface: TableSchema
        Takes a raw DynamoDb SDK representation of a record in a table and maps it to a Java object. A new object is created to fulfil this operation.

        If attributes are missing from the map, that will not cause an error, however if attributes are found in the map which the mapper does not know how to map, an exception will be thrown.

        If all attribute values in the attributeMap are null, null will be returned. Use TableSchema.mapToItem(Map, boolean) instead if you need to preserve empty object.

        API Implementors Note:

        TableSchema.mapToItem(Map, boolean) must be implemented if preserveEmptyObject behavior is desired.

        Specified by:
        mapToItem in interface TableSchema<EnhancedDocument>
        Parameters:
        attributeMap - A map of String to AttributeValue that contains all the raw attributes to map.
        Returns:
        A new instance of a Java object with all the attributes mapped onto it.
        See Also:
        TableSchema.mapToItem(Map, boolean)

      • itemToMap

        public Map<String,​AttributeValue> itemToMap​(EnhancedDocument item,
                                                  boolean ignoreNulls)
        Takes a modelled object and converts it into a raw map of AttributeValue that the DynamoDb low-level SDK can work with. This flag does not have significance for the Document API, unlike Java objects where the default value of an undefined Object is null.In contrast to mapped classes, where a schema is present, the DocumentSchema is unaware of the entire schema.Therefore, if an attribute is not present, it signifies that it is null, and there is no need to handle it in a separate way.However, if the user explicitly wants to nullify certain attributes, then the user needs to set those attributes as null in the Document that needs to be updated.
        Specified by:
        itemToMap in interface TableSchema<EnhancedDocument>
        Parameters:
        item - The modelled Java object to convert into a map of attributes.
        ignoreNulls - If set to true; any null values in the Java object will not be added to the output map. If set to false; null values in the Java object will be added as AttributeValue of type 'nul' to the output map.
        Returns:
        A map of String to AttributeValue representing all the modelled attributes in the model object.

      • itemToMap

        public Map<String,​AttributeValue> itemToMap​(EnhancedDocument item,
                                                  Collection<String> attributes)
        Description copied from interface: TableSchema
        Takes a modelled object and extracts a specific set of attributes which are then returned as a map of AttributeValue that the DynamoDb low-level SDK can work with. This method is typically used to extract just the key attributes of a modelled item and will not ignore nulls on the modelled object.
        Specified by:
        itemToMap in interface TableSchema<EnhancedDocument>
        Parameters:
        item - The modelled Java object to extract the map of attributes from.
        attributes - A collection of attribute names to extract into the output map.
        Returns:
        A map of String to AttributeValue representing the requested modelled attributes in the model object.

      • attributeValue

        public AttributeValue attributeValue​(EnhancedDocument item,
                                     String attributeName)
        Description copied from interface: TableSchema
        Returns a single attribute value from the modelled object.
        Specified by:
        attributeValue in interface TableSchema<EnhancedDocument>
        Parameters:
        item - The modelled Java object to extract the attribute from.
        attributeName - The attribute name describing which attribute to extract.
        Returns:
        A single AttributeValue representing the requested modelled attribute in the model object or null if the attribute has not been set with a value in the modelled object.

      • tableMetadata

        public TableMetadata tableMetadata()
        Description copied from interface: TableSchema
        Returns the object that describes the structure of the table being modelled by the mapper. This includes information such as the table name, index keys and attribute tags.
        Specified by:
        tableMetadata in interface TableSchema<EnhancedDocument>
        Returns:
        A TableMetadata object that contains structural information about the table being modelled.

      • isAbstract

        public boolean isAbstract()
        Description copied from interface: TableSchema
        A boolean value that represents whether this TableSchema is abstract which means that it cannot be used to directly create records as it is lacking required structural elements to map to a table, such as a primary key, but can be referred to and embedded by other schemata.
        Specified by:
        isAbstract in interface TableSchema<EnhancedDocument>
        Returns:
        true if it is abstract, and therefore cannot be used directly to create records but can be referred to by other schemata, and false if it is concrete and may be used to map records directly.