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TacticianBundle

Symfony2 Bundle for the Tactician library https://github.com/thephpleague/tactician/

Installation

Step 1: Download the Bundle

Open a command console, enter your project directory and execute the following command to download the latest stable release for this bundle:

This command requires you to have Composer installed globally, as explained in the installation chapter of the Composer documentation.

Step 2: Enable the Bundle

Then, enable the bundle by adding it to the list of registered bundles in the app/AppKernel.php file of your project:

Using the Command Bus

Create a service and inject the command bus:

Then pass a command to the command bus for execution:

Autowiring

If Symfony autowire feature is enabled (available from Symfony 2.8), instead of creating a service for each controller using the default commandbus you can inject and use it as follows:

Note that this only works for the default commandbus, if you want to inject other than the default one you can override the config through an alias with:

If you have multiple buses, you can use named parameter aliases by using the bus name as part of the parameter name. For example, if you want to inject the command bus named default, name the parameter defaultBus. The syntax always follows {bus_name}Bus.

This feature is only available from Symfony 4.2

Configuring Command Handlers

When you pass a command to Tactician, the ultimate goal is to have it mapped to a Handler.

Since handlers often have extra dependencies and are best lazily-loaded, you'll want to register them in the service container.

There's a few different ways to map your Commands to a Handler, all of which can be combined. We'll walk through them below:

1. Manually Mapping

Let's say we have two classes, RegisterUserCommand and RegisterUserHandler. We'll register the Handler in the service container, along with a repository it needs.

However, we still need to map the Command to the Handler. We can do this by adding a tag to the Handler's DI definition.

The tag should have two attributes: the tag name, which should always be tactician.handler, and the command, which should be the FQCN of the Command.

2. Map Based On Typehints

Rather than repeating the command's full class name, we can also reflect on the Handler's method typehints.

This detects what commands this handler receives by inspecting the class' methods. The rules for matching are:

1. The method must be public.
2. The method must accept only one parameter.
3. The parameter must be typehinted with a class name.

In other words, the RegisterUserHandler class should look like this:

If you have multiple commands going into a single handler, they will all be detected, provided they follow the rules above. The actual name of the method is NOT important.

If you're using typehints AND FQCN mappings, then the FQCN mapping always wins out.

Registering by typehints can be very useful if you're using the autowiring features in the latest versions of Symfony.

3. Custom Mapping Rules

If you'd like to define your own rules for automatically mapping commands to handlers in the container, you can do that as well.

First, implement the Router object you can use to map your commands to your handler services.

There's a good chance that your strategy will involve using container tags of some sort. If that's the case, look into extending the TagBasedMapping abstract class. This will save you some of the boiler plate associated with handling multiple buses.

Once your object is ready, pass it to the TacticianBundle instance when setting your AppKernel.php:

4. Combining Mapping Strategies

If you have multiple strategies you'd like to chain together, you can use the CompositeMapping object to chain them together.

If multiple HandlerMapping strategies detect the same Command, but different Handlers, then the last mentioned mapping strategy wins. Therefore, it's usually best to put your custom strategy last OR the ClassNameMapping last so you can make full overrides when necessary.

5. Write Your Own Middleware

Remember, Tactician is based purely on middleware. If you don't want to mess around with all this and you have a simple convention based way of mapping commands to handlers, just write your own middleware to execute Handlers.

Checking your wiring

You can run the command to get a list of which commands are mapped to which services.

Configuring Middleware

Everything inside Tactician is a middleware plugin. Without any middleware configured, nothing will happen when you pass a command to $commandBus->handle().

By default, the only Middleware enabled is the Command Handler support. You can override this and add your own middleware in the app/config.yml.

Important: Adding your own middleware is absolutely encouraged, just be sure to always add tactician.middleware.command_handler as the final middleware. Otherwise, your commands won't actually be executed.

Check the Tactician docs for more info and a complete list of middleware.

Configuring Multiple Command Buses

The bundle is pre-configured with a command bus called "default", with the service id tactician.commandbus. Some users want to configure more than one command bus though.

Let's say you're integrating a remote accounting system into your application and you'd like to use a separate command bus for just those commands. You can wire up two command buses like this:

You can do this via configuration, like so:

The configuration defines two buses: "default" and "accounting". These buses will be registered as the tactician.commandbus.default and tactician.commandbus.accounting services respectively.

Take note that each bus now has configured their own command handler middleware: tactician.middleware.command_handler for the default and tactician.commandbus.accounting.middleware.command_handler for the account one.

If you want, you can also change which command handler is registered to tactician.commandbus. You can do this by setting the default_bus value in the configuration, like so:

By default, all commands are available in each bus. If you want to make a command available only to a specific bus, you need to specify its id :

and you will be able to handle this command only on the accounting bus:

Extra Bundled Middleware

This bundles ships with a few pre-configured middlewares. To enable them, add them to the middlewares list in your bus configuration (see Configuring Middleware)

Validator Middleware (tactician.middleware.validator)

This middleware uses Symfony's validator to check the command object before passing it along. In practice, this means you can add any Symfony validator annotations to your command to ensure it's fully correct before execution. This isn't a full replacement for writing your objects in an internally consistent style but it can be very helpful.

Constraints can be added via configuration or annotations like in default Symfony practices, please refer to their docs.

If the command fails, it will throw a League\Tactician\Bundle\Middleware\InvalidCommandException. This exception also contains the ConstraintViolationList produced by the validator so you can inspect or log the errors yourself.

Locking Middleware (tactician.middleware.locking)

This middleware is bundled in Tactician, please refer to the official documentation for details.

Logger Middleware (tactician.middleware.logger)

This middleware is bundled in Tactician, please refer to the official documentation for details.

Security Middleware (tactician.middleware.security)

The security middleware will perform authorization on handling all commands. By default an AccessDenied exception will be thrown if the user is not authorized.

This middleware is based on Symfony's AccessDecisionManager and voter system. We recommend familiarizing yourself with it before trying to use this middleware. If you'd like to configure more complex scenarios, consider implementing a custom Symfony voter.

As a precaution, the middleware requires you to register the command in the security configuration before it will be evaluated by Symfony's AccessDecisionManager.

Furthermore, while the security middleware is based on trusted components, we always recommend a defense in depth strategy. Simply hooking your command bus up to a public web endpoint and relying fully on this middleware may not be sufficient coverage for your application.

The Security middleware is disabled by default.

Command Handler Middleware (tactician.middleware.command_handler)

Always ensure this is the last middleware listed

This is the plugin that actually matches your command to a handler and executes it. If you have complex matching logic, feel free to implement your own variant and leave this middleware off.

However, for 99% of users, this should be enabled and set as the last middleware in the list.

Customizing the MethodNameInflector used by the tactician.middleware.command_handler middleware

By default, the bundle uses HandleInflector from Tactician core. That is to say, it expects your Command Handlers to have a handle() method that receives the command to execute.

However, if you prefer a different inflector, you can pass the service name in config.yml.

Tactician core offers a list of custom Inflectors, all of which are supported in this bundle. Assuming a class called My\App\RegisterUserCommand(), the invoked methods on the handler would be:

• tactician.handler.method_name_inflector.handle - handle()
• tactician.handler.method_name_inflector.handle_class_name - handleRegisterUserCommand()
• tactician.handler.method_name_inflector.handle_class_name_without_suffix - handleRegisterUser()
• tactician.handler.method_name_inflector.invoke - __invoke()

While handle() is a reasonable default, using one of the class name methods allows you to handle multiple commands on a single class (possibly useful if they share common dependencies or fit together in some fashion). Likewise, __invoke can be useful if you're mapping to a list of closures.

When using multiple buses, you can also specify the method_inflector of particular bus :

Testing

Security

Disclosure information can be found on the main Tactician repo.

License

The MIT License (MIT). Please see License File for more information.