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Response Processors

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A special filter, mainly used to inject page contributions.

Response processors are only available in the Site Engine

Introduction

Proessors get executed between the component rendring step, and the contributions filter in the site engine pipeline. Response processors are commonly used by apps that need to inject <<page contributions without placing a component on the page.

Use cases are:

  • Dynamically adding page contributions (i.e. script tags)

  • General manipulation of the response markup i.e. headers or body (i.e. adding SEO tags).

Consider using regular HTTP Filters for other use-cases.

Usage

Create a response processor by placing a controller file in you project folder under src/main/resources/site/processors i.e. src/main/resources/site/processors/myprocessor.js

The controller must export a responseProcessor. ResponseProcessors receive both a request and response objects. Below is an example that dynamically adds a bodyEnd page contribution to the response.

processors/tracker.js 
exports.responseProcessor = function (req, res) {
    var trackingScript = '<script src="http://some.cdn/js/tracker.js"></script>';

    // Check if contribution field exists, if not create it
    var bodyEnd = res.pageContributions.bodyEnd;
    if (!bodyEnd) {
        res.pageContributions.bodyEnd = [];
    }

    // Add contribution
    res.pageContributions.bodyEnd.push(trackingScript);

    return res;
};

Triggering

To wire a processor into the execution pipeline, it must be declared in the app’s site descriptor, and the application must be added to the respective site.

site.xml 
<site>
  <processors>
    <response-processor name="tracker" order="10"/> (1) (2)
  </processors>
  <form/>
</site>
----
1 @name indicates name of the controller file
2 @order indicates execution order, lower value means higher priority

Response processors may change any of the values of the response object, including: HTTP status code, response body, HTTP headers, cookies and page contributions. It is also possible to return the response object received without any changes.

Execution order

An application may contain multiple processors. Multiple applications can be added to a Site. When a page is rendered, all processors are ordered and executed accordingly.

The order of execution is determined by the order value (as defined in the site descriptor) combined with the order of the application list within the site.

Processors with a lower order will be executed first (across all apps within the site).

In case there are several filters with the same order number, the position of the applications (as configured on the site) determines the order of execution.

If applyFilters is set to false in the response object, any further response processing or filters will be ignored. Default value is true.

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