5.3. Middleware

Middleware is a concept of allowing pieces of functionality to be injected anywhere at your discretion. Almost like plugins or extensions, the popularity of middleware came from third party vendors being able to quickly plug into applications.

• 5.3.1. Introduction
• 5.3.2. Pre-Processing
• 5.3.3. Error Processing
• 5.3.4. Post Processing
• 5.3.5. API (9)

5.3.1. Introduction

Routes is a kind of middleware interface because you can add functionality using the include method explained before.

Routing Middleware Interface

cradle()->get('/some/path', include('/some/event/handler'));

There are other areas where you may need to plug in to other than the time of routing for example before and after the routing and during an error.

5.3.2. Pre-Processing

Middleware can be inserted before routing with the following example.

cradle()->preprocess(function($request, $response) {
    //Do something before routing
});

Like routing, a $request and a $response will be passed. The usual activity for a ->preprocess() would be populating the $request further, presetting a $response and/or adding more available methods. The Bootstrap heavily uses ->preprocess() for example.

5.3.3. Error Processing

cradle()->error(function($request, $response, $error) {
    //Do something because there was an error
});

With error processors, like pre-processors a $request and a $response will be passed. A third argument called $error will also be passed which will be an Exception object. Error processors should be treated as a last ditch effort to report the error to the user in a nice way.

Because errors that happen in an error handler will throw that error if not caught again.
Bootstrap: Errors presets what happens whens there's an error and your free to change/remove/add on to it.

5.3.4. Post Processing

cradle()->postprocess(function($request, $response, $error) {
    //Do something after the connection is closed
});

Post processors are like pre-processors except that it waits till the user has received a response and the connection is closed before being activated. This is a nice feature where you can do short time consuming tasks if you do not have access to a queue available.

 A caveat about post-processors is that writing to sessions will no longer be
 available. You can write to it, but on refresh, it won't remember it like if
 it was still open.

5.3.5. API

preprocess - Adds pre processing middleware which is called before routing

cradle()->preprocess(function($request, $response) {
    //Do something before routing
});

error - Adds error middleware which is called when an Exception is thrown

cradle()->error(function($request, $response) {
    //Do something because there was an error
});

postprocess - Adds post processing after the response was sent out and the connection is closed

cradle()->postprocess(function($request, $response) {
    //Do something after the connection is closed
});

setPreprocessor - Allows for a custom pre processor to be used

cradle()->setPreProcessor(new Cradle\Http\Middleware);

getPreProcessor - Returns a Middleware processor if none was set, it will auto create one

cradle()->getPreprocessor();

setErrorProcessor - Allows for a custom error processor to be used

cradle()->setErrorProcessor(new Cradle\Http\Middleware);

getErrorProcessor - Returns a Middleware processor if none was set, it will auto create one

cradle()->getErrorProcessor();

setPostProcessor - Allows for a custom post processor to be used

cradle()->setPostProcessor(new Cradle\Http\Middleware);

getPostProcessor - Returns a Middleware processor if none was set, it will auto create one

cradle()->getPostProcessor();