Workshop utilities

For the workshops that I organize, I often need some “utilities” that will do the job, but are as simple as possible. Examples of such utilities are:

• Something to dispatch events with.
• Something to serialize and deserialize objects with.
• Something to store and load objects with.
• Something to use with event sourcing (an event store, an event-sourced repository).

I put several of these tools in a code base called php-workshop-tools. These utilities should be small, and very easy to understand and use. They will be different from the frameworks and libraries most workshop participants usually use, but they should offer more or less the same functionality. While designing these tools, I was constantly looking for the golden mean:

The JMSSerializerBundle has a VersionExclusionStrategy, which allows you to serialize/deserialize objects for a specific version of your API. You can mark the properties that are available for different versions using the @Since and @Until annotations:

use JMS\SerializerBundle\Annotation\Type;
use JMS\SerializerBundle\Annotation\Since;
use JMS\SerializerBundle\Annotation\Until;

class Comment
{
    /**
     * @Type("DateTime")
     * @Since("1.2.0")
     */
    private $createdAt;

    /**
     * @Type("DateTime")
     * @Until("2.1.3")
     */
    private $updatedAt;
}

The only thing you have to do is tell the serializer which version to use, before you start using it:

In my previous post I wrote about a listener that deserializes the request content and replaces controller arguments with the result. Johannes Schmitt made the suggestion to use a ParamConverter for this. This of course makes sense: currently there is only a ParamConverter for converting some “id” argument into an entity with the same id (see the documentation for @ParamConverter.

In this post I will show you how to create your own ParamConverter and how we can specialize it in deserializing request content.

Based on the list of most popular search results leading to my blog, using Symfony2 for building some kind of webservice seems to be quite “hot”. It also seems many people are struggling with the question how they should serialize their content to and from XML and/or JSON. Two beautiful bundles are already available for this, FOSRestBundle and JMSSerializerBundle. Both will help you a lot with this issue, by providing transparent conversion between formats for both the request content and the response body. Nevertheless, a few things are missing. For example, I want to really serialize and deserialize objects, for example, when I send a request with a comment (or part of it) like this:

I was looking for a way to serialize domain objects into JSON strings and back again into objects of the original class. This is essential for webservices, especially those built around the JSON-RPC specification that allow clients to make calls to their server and, for example add new personal data to their database of contacts. It makes life a lot easier when this data matches the field names and inner structure of your own domain objects. For example, a JSON string like {"name":"Matthias Noback"} should be easily translatable to an object of class Acme\Webservice\Entity\Person with a private property name. But how do you know which class to instantiate, when you only have the simple JSON string above?