Package org.axonframework.messaging.queryhandling

Class SimpleQueryUpdateEmitter

java.lang.Object

org.axonframework.messaging.queryhandling.SimpleQueryUpdateEmitter

All Implemented Interfaces:

DescribableComponent, QueryUpdateEmitter

public class SimpleQueryUpdateEmitter
extends Object
implements QueryUpdateEmitter

Simple implementation of the QueryUpdateEmitter, delegating operations to a QueryBus for emitting update, completing subscription queries, and completing subscription queries exceptionally.

Uses the ProcessingContext given during construction of the SimpleQueryUpdateEmitter to perform all operations in the expected lifecycle order.

Since:

4.0.0

Author:

Milan Savic, Stefan Dragisic, Steven van Beelen

Field Summary

Fields inherited from interface org.axonframework.messaging.queryhandling.QueryUpdateEmitter

RESOURCE_KEY

Constructor Summary

Constructors

Constructor	Description
SimpleQueryUpdateEmitter(QueryBus queryBus, MessageTypeResolver messageTypeResolver, MessageConverter converter, ProcessingContext context)	Construct a SimpleQueryUpdateEmitter with the given messageTypeResolver, queryBus, and context.

Method Summary

Modifier and Type	Method	Description
<Q> void	complete(Class<Q> queryType, Predicate<? super Q> filter)	Completes subscription queries matching the given queryType and filter.
void	complete(QualifiedName queryName, Predicate<Object> filter)	Completes subscription queries matching the given queryName and filter.
<Q> void	completeExceptionally(Class<Q> queryType, Predicate<? super Q> filter, Throwable cause)	Completes subscription queries with the given cause matching given queryType and filter.
void	completeExceptionally(QualifiedName queryName, Predicate<Object> filter, Throwable cause)	Completes subscription queries with the given cause matching given queryName and filter.
void	describeTo(ComponentDescriptor descriptor)	Describe the properties of this DescribableComponent with the given descriptor.
<Q> void	emit(Class<Q> queryType, Predicate<? super Q> filter, Supplier<Object> updateSupplier)	Emits the outcome of the updateSupplier to subscription queries matching the given queryType and given filter.
void	emit(QualifiedName queryName, Predicate<Object> filter, Supplier<Object> updateSupplier)	Emits the outcome of the updateSupplier to subscription queries matching the given queryName and given filter.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.axonframework.messaging.queryhandling.QueryUpdateEmitter

emit, emit

Constructor Details

SimpleQueryUpdateEmitter

public SimpleQueryUpdateEmitter(QueryBus queryBus,
 MessageTypeResolver messageTypeResolver,
 MessageConverter converter,
 ProcessingContext context)

Construct a SimpleQueryUpdateEmitter with the given messageTypeResolver, queryBus, and context.

The messageTypeResolver is used to construct update messages for QueryUpdateEmitter.emit(Class, Predicate, Object) invocations. Any QueryUpdateEmitter.emit(Class, Predicate, Object) or QueryUpdateEmitter.emit(QualifiedName, Predicate, Object) is delegated to QueryBus.emitUpdate(Predicate, Supplier, ProcessingContext). Similarly, complete(Class, Predicate)/complete(QualifiedName, Predicate) and completeExceptionally(Class, Predicate, Throwable)/completeExceptionally(QualifiedName, Predicate, Throwable) are respectively delegated to QueryBus.completeSubscriptions(Predicate, ProcessingContext) and QueryBus.completeSubscriptionsExceptionally(Predicate, Throwable, ProcessingContext).

Parameters:

queryBus - The QueryBus to delegate the QueryUpdateEmitter.emit(Class, Predicate, Object), complete(Class, Predicate), and completeExceptionally(Class, Predicate, Throwable) invocations to.

messageTypeResolver - The MessageType resolver used to construct update messages for QueryUpdateEmitter.emit(Class, Predicate, Object) invocations

converter - The MessageConverter used to convert the payload whenever a filter is used based on a concrete type. For example, through QueryUpdateEmitter.emit(Class, Predicate, Object).

context - The ProcessingContext within which update are emitted, subscription query are completed, and subscription queries are completed exceptionally in.

Method Details

emit

public <Q> void emit(Class<Q> queryType,
 Predicate<? super Q> filter,
 Supplier<Object> updateSupplier)

Description copied from interface: QueryUpdateEmitter

Emits the outcome of the updateSupplier to subscription queries matching the given queryType and given filter.

The updateSupplier is only invoked whenever there are matching queries.

Specified by:

emit in interface QueryUpdateEmitter

Type Parameters:

Q - The type of the QueryMessage to filter on.

Parameters:

queryType - The type of the QueryMessage to filter on.

filter - A predicate to filter matching subscription queries based on the Message.payload() converted to the given queryType

updateSupplier - The update supplier to emit for subscription queries matching the given queryType and filter.

emit

public void emit(QualifiedName queryName,
 Predicate<Object> filter,
 Supplier<Object> updateSupplier)

Description copied from interface: QueryUpdateEmitter

Emits the outcome of the updateSupplier to subscription queries matching the given queryName and given filter.

The updateSupplier is only invoked whenever there are matching queries.

Specified by:

emit in interface QueryUpdateEmitter

Parameters:

queryName - The qualified name of the Message.type() to filter on.

filter - A predicate to filter matching subscription queries based on the raw Message.payload().

updateSupplier - The update supplier to emit for subscription queries matching the given queryName and filter.

complete

public <Q> void complete(Class<Q> queryType,
 Predicate<? super Q> filter)

Description copied from interface: QueryUpdateEmitter

Completes subscription queries matching the given queryType and filter.

Specified by:

complete in interface QueryUpdateEmitter

Type Parameters:

Q - The type of the QueryMessage to filter on.

Parameters:

queryType - The type of the QueryMessage to filter on.

filter - A predicate to filter matching subscription queries based on the Message.payload() converted to the given queryType

complete

public void complete(QualifiedName queryName,
 Predicate<Object> filter)

Description copied from interface: QueryUpdateEmitter

Completes subscription queries matching the given queryName and filter.

Specified by:

complete in interface QueryUpdateEmitter

Parameters:

queryName - The qualified name of the Message.type() to filter on.

filter - A predicate testing the raw Message.payload() as is.

completeExceptionally

public <Q> void completeExceptionally(Class<Q> queryType,
 Predicate<? super Q> filter,
 Throwable cause)

Description copied from interface: QueryUpdateEmitter

Completes subscription queries with the given cause matching given queryType and filter.

Specified by:

completeExceptionally in interface QueryUpdateEmitter

Type Parameters:

Q - The type of the QueryMessage to filter on.

Parameters:

queryType - The type of the QueryMessage to filter on.

filter - A predicate to filter matching subscription queries based on the Message.payload() converted to the given queryType

cause - The cause of an error leading to exceptionally complete subscription queries.

completeExceptionally

public void completeExceptionally(QualifiedName queryName,
 Predicate<Object> filter,
 Throwable cause)

Description copied from interface: QueryUpdateEmitter

Completes subscription queries with the given cause matching given queryName and filter.

Specified by:

completeExceptionally in interface QueryUpdateEmitter

Parameters:

queryName - The qualified name of the Message.type() to filter on.

filter - A predicate to filter matching subscription queries based on the raw Message.payload().

cause - The cause of an error leading to exceptionally complete subscription queries.

describeTo

public void describeTo(ComponentDescriptor descriptor)

Description copied from interface: DescribableComponent

Describe the properties of this DescribableComponent with the given descriptor.

Components should call the appropriate describeProperty methods on the descriptor to register their properties. The descriptor is responsible for determining how these properties are formatted and structured in the final output.

Best Practices: As a general rule, all relevant fields of a DescribableComponent implementation should be described in this method. However, developers have discretion to include only the fields that make sense in the context. Not every field may be meaningful for description purposes, especially internal implementation details. Furthermore, components might want to expose different information based on their current state. The final decision on what properties to include lies with the person implementing the describeTo method, who should focus on providing information that is useful for understanding the component's configuration and state.

Example implementation:

 public void describeTo(ComponentDescriptor descriptor) {
     descriptor.describeProperty("name", this.name);
     descriptor.describeProperty("enabled", this.enabled);
     descriptor.describeProperty("configuration", this.configuration); // A nested component
     descriptor.describeProperty("handlers", this.eventHandlers);      // A collection
 }
 

Specified by:

describeTo in interface DescribableComponent

Parameters:

descriptor - The component descriptor to describe this DescribableComponentn its properties in.