software.amazon.awssdk.extensions.dynamodb.mappingclient

Interface MapperExtension

All Known Implementing Classes:

ChainMapperExtension, VersionedRecordExtension

public interface MapperExtension

Interface for extending the mapper. Two hooks are provided, one that is called just before a record is written to the database, and one called just after a record is read from the database. This gives the extension the opportunity to act as an invisible layer between the application and the database and transform the data accordingly.

Only one extension can be loaded with a mapped table. In order to combine multiple extensions, the ChainMapperExtension should be used and initialized with all the component extensions to combine together into a chain.

Method Summary

Modifier and Type	Method and Description
default ReadModification	afterRead(Map<String,AttributeValue> item, OperationContext operationContext, TableMetadata tableMetadata) This hook is called just after an operation that has read data from the database.
default WriteModification	beforeWrite(Map<String,AttributeValue> item, OperationContext operationContext, TableMetadata tableMetadata) This hook is called just before an operation is going to write data to the database.

Method Detail

beforeWrite

default WriteModification beforeWrite(Map<String,AttributeValue> item,
                                      OperationContext operationContext,
                                      TableMetadata tableMetadata)

This hook is called just before an operation is going to write data to the database. The extension that implements this method can choose to transform the item itself, or add a condition to the write operation or both.

Parameters:

item - The item that is about to be written.

operationContext - The context under which the operation to be modified is taking place.

tableMetadata - The structure of the table.

Returns:

A WriteModification object that can alter the behavior of the write operation.

afterRead

default ReadModification afterRead(Map<String,AttributeValue> item,
                                   OperationContext operationContext,
                                   TableMetadata tableMetadata)

This hook is called just after an operation that has read data from the database. The extension that implements this method can choose to transform the item, and then it is the transformed item that will be mapped back to the application instead of the item that was actually read from the database.

Parameters:

item - The item that has just been read.

operationContext - The context under which the operation to be modified is taking place.

tableMetadata - The structure of the table.

Returns:

A ReadModification object that can alter the results of a read operation.