org.axonframework.eventhandling.deadletter

Class DeadLetteringEventHandlerInvoker.Builder

java.lang.Object

org.axonframework.eventhandling.SimpleEventHandlerInvoker.Builder<DeadLetteringEventHandlerInvoker.Builder>

org.axonframework.eventhandling.deadletter.DeadLetteringEventHandlerInvoker.Builder

Enclosing class:

DeadLetteringEventHandlerInvoker

public static class DeadLetteringEventHandlerInvoker.Builder
extends SimpleEventHandlerInvoker.Builder<DeadLetteringEventHandlerInvoker.Builder>

Builder class to instantiate a DeadLetteringEventHandlerInvoker.

The EnqueuePolicy defaults to returning Decisions.enqueue(Throwable) that truncates the Throwable.getMessage() size to 1024 characters when invoked for any dead letter, the ListenerInvocationErrorHandler is defaulted to a PropagatingErrorHandler, the SequencingPolicy to a SequentialPerAggregatePolicy, allowReset defaults to false, sequenceIdentifierCacheEnabled defaults to false and sequenceIdentifierCacheSize used defaults to 1024. Providing at least one Event Handler, a SequencedDeadLetterQueue, and a TransactionManager are hard requirements and as such should be provided.

Method Summary

Modifier and Type	Method and Description
DeadLetteringEventHandlerInvoker.Builder	allowReset(boolean allowReset) Sets whether this DeadLetteringEventHandlerInvoker supports resets of the provided SequencedDeadLetterQueue.
DeadLetteringEventHandlerInvoker	build() Initializes a DeadLetteringEventHandlerInvoker as specified through this Builder.
DeadLetteringEventHandlerInvoker.Builder	enableSequenceIdentifierCache() Enabled this DeadLetteringEventHandlerInvoker to cache sequence identifiers.
DeadLetteringEventHandlerInvoker.Builder	enqueuePolicy(EnqueuePolicy<EventMessage<?>> enqueuePolicy) Sets the EnqueuePolicy this EventHandlerInvoker uses to decide whether a dead letter should be added to the SequencedDeadLetterQueue.
DeadLetteringEventHandlerInvoker.Builder	queue(SequencedDeadLetterQueue<EventMessage<?>> queue) Sets the SequencedDeadLetterQueue this EventHandlerInvoker maintains dead letters with.
DeadLetteringEventHandlerInvoker.Builder	sequenceIdentifierCacheSize(int sequenceIdentifierCacheSize) Sets the size of the cache.
DeadLetteringEventHandlerInvoker.Builder	transactionManager(TransactionManager transactionManager) Sets the TransactionManager used by this invoker for all operations involving the configured SequencedDeadLetterQueue.
protected void	validate() Validate whether the fields contained in this Builder are set accordingly.

Methods inherited from class org.axonframework.eventhandling.SimpleEventHandlerInvoker.Builder

eventHandlers, eventHandlers, handlerDefinition, listenerInvocationErrorHandler, parameterResolverFactory, sequencingPolicy, wrapEventMessageHandler

Methods inherited from class java.lang.Object

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

Method Detail

queue

public DeadLetteringEventHandlerInvoker.Builder queue(@Nonnull
                                                      SequencedDeadLetterQueue<EventMessage<?>> queue)

Sets the SequencedDeadLetterQueue this EventHandlerInvoker maintains dead letters with.

Parameters:

queue - The SequencedDeadLetterQueue this EventHandlerInvoker maintains dead letters with.

Returns:

The current Builder instance for fluent interfacing.

enqueuePolicy

public DeadLetteringEventHandlerInvoker.Builder enqueuePolicy(EnqueuePolicy<EventMessage<?>> enqueuePolicy)

Sets the EnqueuePolicy this EventHandlerInvoker uses to decide whether a dead letter should be added to the SequencedDeadLetterQueue. Defaults to returning Decisions.enqueue(Throwable) that truncates the Throwable.getMessage() size to 1024 characters when invoked for any dead letter.

Parameters:

enqueuePolicy - The EnqueuePolicy this EventHandlerInvoker uses to decide whether a dead letter should be added to the SequencedDeadLetterQueue.

Returns:

The current Builder, for fluent interfacing.

transactionManager

public DeadLetteringEventHandlerInvoker.Builder transactionManager(@Nonnull
                                                                   TransactionManager transactionManager)

Sets the TransactionManager used by this invoker for all operations involving the configured SequencedDeadLetterQueue.

Parameters:

transactionManager - The TransactionManager used by this invoker for all operations involving the configured SequencedDeadLetterQueue

Returns:

The current Builder instance for fluent interfacing.

allowReset

public DeadLetteringEventHandlerInvoker.Builder allowReset(boolean allowReset)

Sets whether this DeadLetteringEventHandlerInvoker supports resets of the provided SequencedDeadLetterQueue. If set to true, SequencedDeadLetterQueue.clear() will be invoked upon a SimpleEventHandlerInvoker.performReset()/SimpleEventHandlerInvoker.performReset(Object) invocation. Defaults to false.

Parameters:

allowReset - A toggle dictating whether this DeadLetteringEventHandlerInvoker supports resets of the provided SequencedDeadLetterQueue.

Returns:

The current Builder instance for fluent interfacing.

enableSequenceIdentifierCache

public DeadLetteringEventHandlerInvoker.Builder enableSequenceIdentifierCache()

Enabled this DeadLetteringEventHandlerInvoker to cache sequence identifiers. If enabled, it will create a SequenceIdentifierCache per segment. The cache prevents calling SequencedDeadLetterQueue.enqueueIfPresent(Object, Supplier) when we can be sure the sequence identifier is not present.

This can happen in two cases. Either we start with an empty SequencedDeadLetterQueue, and we haven't enqueued this identifier yet. Or the queue was not empty at the start. In this case, we can skip the identifier once we checked that we did not enqueue it before. If the identifier might be present, we always call the SequencedDeadLetterQueue#enqueueIfPresent(Object, Supplier)} as the sequence might have been cleaned up in the meantime.

Returns:

The current Builder instance for fluent interfacing.

sequenceIdentifierCacheSize

public DeadLetteringEventHandlerInvoker.Builder sequenceIdentifierCacheSize(int sequenceIdentifierCacheSize)

Sets the size of the cache. When there are already sequences stored in a dead-letter queue, we need to check for each sequence identifier if it's already included. This result is stored so we can skip a second "is enqueued" check when we encounter the same sequence identifier. This method thus limits memory use of the cache. The size defaults to 1024.

If you have a lot of long-living aggregates, it might improve performance to increase the cache size at the cost of more memory use. If you only have aggregates that are short-lived, setting it to a lower value frees up memory, while it might not affect performance.

This setting is applied per Segment. Note that this setting will only be used in combination with enableSequenceIdentifierCache(), and when the SequencedDeadLetterQueue is not empty when constructing the cache.

Parameters:

sequenceIdentifierCacheSize - The size to keep track of sequence identifiers which are not present.

Returns:

The current Builder instance for fluent interfacing.

build

public DeadLetteringEventHandlerInvoker build()

Initializes a DeadLetteringEventHandlerInvoker as specified through this Builder.

Overrides:

build in class SimpleEventHandlerInvoker.Builder<DeadLetteringEventHandlerInvoker.Builder>

Returns:

A DeadLetteringEventHandlerInvoker as specified through this Builder.

validate

protected void validate()

Validate whether the fields contained in this Builder are set accordingly.

Overrides:

validate in class SimpleEventHandlerInvoker.Builder<DeadLetteringEventHandlerInvoker.Builder>

Throws:

AxonConfigurationException - When one field asserts to be incorrect according to the Builder's specifications.