Universal structure or service for API to API Conversion - php

Question

As part of an App i'm developing there's a requirement to create a conversion between our RESTful JSON API and a number of other formats. The intention is to allow output from our API to be converted to make further requests to API's that use different formats such as SOAP, or other REST based API's with different requirements.
A few examples of the kind of things I think this might need to do:
manipulate the JSON output to use different keys (and maybe only a subset of
data
convert to an XML packet/document
convert to a valid SOAP request
output data as a specific filetype/structure (such as csv)
I'm interested really in what approaches should I be looking at here. It would seem to me that this should be a fairly common request so i'm interested if there are specific libraries I should look at, or existing services perhaps. If such a service doesn't exist then ideally I want to create a common structure whereby the 2 disparate services can be mapped using a universal set of tools that are just then configured to work together. This will be within a Laravel PHP application so any Composer compatible library would work.

Answer 1

Following on from my comment:
"I am not aware of any such library to do this, but as a rough guide I think you probably want to create some kind of adapters which all use a common interface. These adapters can then be written to deal with the conversion you are trying to achieve via some open-source library. Manipulating the output might be a good excuse to use the decorator pattern :) Sorry I could not be of much more help."
An example of what I think you are after is the following:
An interface for your adapters
interface DataConvertor
{
public function convert(DataInterface $data);
}
An interface for the data you are passing around (the data will be an object also with a common interface to work from).
interface DataInterface
{
/**
* returns a json string
*/
public function asJson();
}
Then you can create your adapter for use with some 3rd party library.
class SomeThirdPartyNameAdapter implements DataConvertor
{
public function convert($data)
{
//some logic here to make my data object with a known asJon method
//suitable for use for some 3rd party library, and use that library.
$rawJson = $data->asJson();
//manipulate this as needed ($compatibleData)
$thirdPartyLib = new ThirdPartyLib();
return $thirdPartyLib->thirdPartyMethod($compatibleData);
}
}
Obviously this is just a rough guide and there may be other parts of this you can make abstract (e.g. have the adapters implement the DataConvertor interface but also extend some abstract class to inherit some functionality, or other method to add to your interface).
Hope this helps

Answer 2

Carl is right that a great approach is to create some adapters using a common interface. Then you can provide implementations that convert JSON to XML or JSON to a CSV, etc.
However I would strongly recommend looking into Mule ESB as a solution as well. http://www.mulesoft.org/
It's a Java based, open source project that allows you to do pretty quick and efficient integrations. For example, you could create a "flow" (a Mule term) that makes a RESTful call and then converts the data and pumps it out to a specific destination (CSV, SOAP call, XML, etc.)
The real selling points of Mule (things that have worked great for me):
Very easy to deploy. It works similar to something like Tomcat, where you can deploy a package and it runs on a server.
Tons and tons and tons of boilerplate code already done for you.
Free and stable. They have tons of high profile customers so it's pretty battle tested and we've been able to get their free version working in production with no trouble.