software.amazon.awssdk.enhanced.dynamodb.extensions

Class AtomicCounterExtension

java.lang.Object

software.amazon.awssdk.enhanced.dynamodb.extensions.AtomicCounterExtension

All Implemented Interfaces:

DynamoDbEnhancedClientExtension

public final class AtomicCounterExtension
extends Object
implements DynamoDbEnhancedClientExtension

This extension enables atomic counter attributes to be changed in DynamoDb by creating instructions for modifying an existing value or setting a start value. The extension is loaded by default when you instantiate a DynamoDbEnhancedClient and only needs to be added to the client if you are adding custom extensions to the client.

To utilize atomic counters, first create a field in your model that will be used to store the counter. This class field should of type Long and you need to tag it as an atomic counter:

• If you are using the BeanTableSchema, you should annotate with DynamoDbAtomicCounter
• If you are using the StaticTableSchema, use the StaticAttributeTags.atomicCounter() static attribute tag.

Every time a new update of the record is successfully written to the database, the counter will be updated automatically. By default, the counter starts at 0 and increments by 1 for each update. The tags provide the capability of adjusting the counter start and increment/decrement values such as described in DynamoDbAtomicCounter.

Example 1: Using a bean based table schema

 {@code

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AtomicCounterExtension.Builder

Method Summary

Modifier and Type	Method and Description
WriteModification	beforeWrite(DynamoDbExtensionContext.BeforeWrite context) This hook is called just before an operation is going to write data to the database.
static AtomicCounterExtension.Builder	builder()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClientExtension

afterRead

Method Detail

builder

public static AtomicCounterExtension.Builder builder()

beforeWrite

public WriteModification beforeWrite(DynamoDbExtensionContext.BeforeWrite context)

Description copied from interface: DynamoDbEnhancedClientExtension

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.

Specified by:

beforeWrite in interface DynamoDbEnhancedClientExtension

Parameters:

context - The DynamoDbExtensionContext.BeforeWrite context containing the state of the execution.

Returns:

WriteModification contains an update expression representing the counters.