얘기 좀 하자.cqrs의 Dispatcher

순서

본고는 주로 go를 연구한다.cqrs의 Dispatcher

Dispatcher

type Dispatcher interface {
    Dispatch(CommandMessage) error
    RegisterHandler(CommandHandler, ...interface{}) error
}

Dispatcher 인터페이스는 Dispatch, RegisterHandler 방법을 정의합니다.

InMemoryDispatcher

type InMemoryDispatcher struct {
    handlers map[string]CommandHandler
}

//NewInMemoryDispatcher constructs a new in memory dispatcher
func NewInMemoryDispatcher() *InMemoryDispatcher {
    b := &InMemoryDispatcher{
        handlers: make(map[string]CommandHandler),
    }
    return b
}

//Dispatch passes the CommandMessage on to all registered command handlers.
func (b *InMemoryDispatcher) Dispatch(command CommandMessage) error {
    if handler, ok := b.handlers[command.CommandType()]; ok {
        return handler.Handle(command)
    }
    return fmt.Errorf("The command bus does not have a handler for commands of type: %s", command.CommandType())
}

//RegisterHandler registers a command handler for the command types specified by the
//variadic commands parameter.
func (b *InMemoryDispatcher) RegisterHandler(handler CommandHandler, commands ...interface{}) error {
    for _, command := range commands {
        typeName := typeOf(command)
        if _, ok := b.handlers[typeName]; ok {
            return fmt.Errorf("Duplicate command handler registration with command bus for command of type: %s", typeName)
        }
        b.handlers[typeName] = handler
    }
    return nil
}

InMemoryDispatcher는 map[string]CommandHandler 속성을 정의하고 디스패치 방법은command에 따릅니다.CommandType()에서 handler를 가져와서 handler를 실행합니다.Handle(command);그 RegisterHandler 방법은commands를 두루 훑어보고command의 type을 가져와map[string]CommandHandler에 하나씩 등록합니다

CommandHandler

// CommandHandler is the interface that all command handlers should implement.
type CommandHandler interface {
    Handle(CommandMessage) error
}

// CommandMessage is the interface that a command message must implement.
type CommandMessage interface {

    // AggregateID returns the ID of the Aggregate that the command relates to
    AggregateID() string

    // Headers returns the key value collection of headers for the command.
    Headers() map[string]interface{}

    // SetHeader sets the value of the header specified by the key
    SetHeader(string, interface{})

    // Command returns the actual command which is the payload of the command message.
    Command() interface{}

    // CommandType returns a string descriptor of the command name
    CommandType() string
}

CommandHandler 인터페이스는 Handle 방법을 정의합니다.CommandMessage 인터페이스는 AggregateID, Headers, SetHeader, Command, CommandType 방법을 정의합니다.

작은 매듭

go.cqrs의 Dispatcher 인터페이스는 디스패치, RegisterHandler 방법을 정의합니다.InMemoryDispatcher는 map[string]CommandHandler 속성을 정의하고 디스패치 방법은command에 따릅니다.CommandType()에서 handler를 가져와서 handler를 실행합니다.Handle(command);그 RegisterHandler 방법은commands를 두루 훑어보고command의 type을 가져와map[string]CommandHandler에 하나씩 등록합니다.

doc

go.cqrs