In software, Apache Cocoon, typically just called Cocoon, is a web application framework built around the concepts of pipeline, separation of concerns and component-based web development. The framework focuses on XML and XSLT publishing and is built using the Java programming language. The flexibility afforded by relying heavily on XML allows rapid content publishing in a variety of formats including HTML, PDF, and WML. The content management systems Apache Lenya and Daisy have been created on top of the framework. Cocoon is also frequently used as a data warehousing ETL tool or as middleware for transporting data between systems.

Sitemap

The sitemap is at the core of Cocoon. It's here that the web site developer configures the different Cocoon components, and defines the Client/Server interactions in what Cocoon refers to as the Pipeline.

Components

The components within Cocoon are grouped by function.

Matchers

Matchers are used to match user requests such as URLs or cookies against wildcard or regular expression patterns. Each user request is sent through the pipeline until a match is made. It is from here that a specific request is processed.

Generators

Generators create a stream of data for further processing. This stream can be generated from an existing XML document or there are generators that can create XML from scratch to represent something on the server, such as a directory structure or image data.

Transformers

Transformers take a stream of data and change them in some way. The most common transformations are performed with XSLT to change one xml format into another. But there are also transformers that take other forms of data (SQL for example).

Serializers

A serializer takes a data stream, makes any required changes, and sends it to the client. There are serializers that allow you to send the data in many different formats including HTML, XHTML, PDF, RTF, SVG, WML and plain text, for example.

Selectors

Selectors offer the same capabilities as a switch statement. They are able to select specific elements of a request and choose the correct pipeline part to use.

Views

Views are mainly used for testing. A view is an exit point in a pipeline. It's possible to put out the XML-Stream which is produced till this point. So you can see if the application is working right.

Readers

Publish content without parsing it (no XML processing). Used for images and such.

Actions

Actions are Java classes that execute some business logic or manage new content production.

An XSP page is a Cocoon XML document containing tag-based directives that specify how to generate dynamic content at request time.

Upon Cocoon processing, these directives are replaced by generated content so that the resulting, augmented XML document can be subject to further processing (typically an XSLT transformation).

XSP pages are transformed into Cocoon producers, typically as Java classes, though any scripting language for which a Java-based processor exists could also be used.

Directives can be either XSP built-in processing tags or user-defined library tags. XSP built-in tags are used to embed procedural logic, substitute expressions and dynamically build XML nodes. User-defined library tags act as templates that dictate how program code is generated from information encoded in each dynamic tag.

The Pipeline

The Pipeline is used to define how the different Cocoon components interact with different requests to produce a response.

See also XProc models and standardization.