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本文次要钻研一下go.cqrs的Dispatcher

Dispatcher

type Dispatcher interface {    Dispatch(CommandMessage) error    RegisterHandler(CommandHandler, ...interface{}) error}
Dispatcher接口定义了Dispatch、RegisterHandler办法

InMemoryDispatcher

type InMemoryDispatcher struct {    handlers map[string]CommandHandler}//NewInMemoryDispatcher constructs a new in memory dispatcherfunc 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}
InMemoryDispatcher定义了map[string]CommandHandler属性，其Dispatch办法依据command.CommandType()获取handler，而后执行handler.Handle(command)；其RegisterHandler办法遍历commands，而后获取command的type，挨个注册到map[string]CommandHandler中

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接口定义了Handle办法；CommandMessage接口定义了AggregateID、Headers、SetHeader、Command、CommandType办法

小结

go.cqrs的Dispatcher接口定义了Dispatch、RegisterHandler办法；InMemoryDispatcher定义了map[string]CommandHandler属性，其Dispatch办法依据command.CommandType()获取handler，而后执行handler.Handle(command)；其RegisterHandler办法遍历commands，而后获取command的type，挨个注册到map[string]CommandHandler中。

doc

  • go.cqrs