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本文次要钻研一下 go.cqrs 的 EventHandler
EventHandler
type EventHandler interface {Handle(EventMessage)
}
EventHandler 定义了 Handle 办法
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 接口定义了 AggregateID、GetHeaders、SetHeader、Event、EventType、Version 办法
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 descriptor
func 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 key
func (c *EventDescriptor) SetHeader(key string, value interface{}) {c.headers[key] = value
}
// Event the event payload of the event message
func (c *EventDescriptor) Event() interface{} {return c.event}
// Version returns the version of the event
func (c *EventDescriptor) Version() *int {return c.version}
EventDescriptor 定义了 id、event、headers、version 属性,它实现了 EventMessage 接口
PublishEvent
// PublishEvent publishes events to all registered event handlers
func (b *InternalEventBus) PublishEvent(event EventMessage) {if handlers, ok := b.eventHandlers[event.EventType()]; ok {
for handler := range handlers {handler.Handle(event)
}
}
}
InternalEventBus 的 PublishEvent 办法会遍历指定 event.EventType() 的 handlers,挨个执行 handler.Handle(event) 办法
小结
go.cqrs 的 EventHandler 定义了 Handle 办法;InternalEventBus 的 PublishEvent 办法会遍历指定 event.EventType() 的 handlers,挨个执行 handler.Handle(event) 办法。
doc
- go.cqrs
正文完