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本文主要研究一下go。cqrs的EventHandler
EventHandler
type EventHandler interface { Handle(EventMessage)}
EventHandler定義了Handle方法
EventMessage
// EventMessage is the interface that a command must implement。type EventMessage interface { // AggregateID returns the ID of the Aggregate that the event relates to AggregateID() string // GetHeaders returns the key value collection of headers for the event。 // // Headers are metadata about the event that do not form part of the // actual event but are still required to be persisted alongside the event。 GetHeaders() map[string]interface{} // SetHeader sets the value of the header specified by the key SetHeader(string, interface{}) // Returns the actual event which is the payload of the event message。 Event() interface{} // EventType returns a string descriptor of the command name EventType() string // Version returns the version of the event Version() *int}
EventMessage介面定義了AggregateID、GetHeaders、SetHeader、Event、EventType、Version方法
EventDescriptor
// EventDescriptor is an implementation of the event message interface。type EventDescriptor struct { id string event interface{} headers map[string]interface{} version *int}// NewEventMessage returns a new event descriptorfunc NewEventMessage(aggregateID string, event interface{}, version *int) *EventDescriptor { return &EventDescriptor{ id: aggregateID, event: event, headers: make(map[string]interface{}), version: version, }}// EventType returns the name of the event type as a string。func (c *EventDescriptor) EventType() string { return typeOf(c。event)}// AggregateID returns the ID of the Aggregate that the event relates to。func (c *EventDescriptor) AggregateID() string { return c。id}// GetHeaders returns the headers for the event。func (c *EventDescriptor) GetHeaders() map[string]interface{} { return c。headers}// SetHeader sets the value of the header specified by the keyfunc (c *EventDescriptor) SetHeader(key string, value interface{}) { c。headers[key] = value}// Event the event payload of the event messagefunc (c *EventDescriptor) Event() interface{} { return c。event}// Version returns the version of the eventfunc (c *EventDescriptor) Version() *int { return c。version}
EventDescriptor定義了id、event、headers、version屬性,它實現了EventMessage介面
PublishEvent
// PublishEvent publishes events to all registered event handlersfunc (b *InternalEventBus) PublishEvent(event EventMessage) { if handlers, ok := b。eventHandlers[event。EventType()]; ok { for handler := range handlers { handler。Handle(event) } }}
InternalEventBus的PublishEvent方法會遍歷指定event。EventType()的handlers,挨個執行handler。Handle(event)方法
小結
go。cqrs的EventHandler定義了Handle方法;InternalEventBus的PublishEvent方法會遍歷指定event。EventType()的handlers,挨個執行handler。Handle(event)方法。
doc
go。cqrs