JCR and Sling Quick Dive

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JCR & Sling quick divePaolo Mo"adelli | Senior Sales Engineer

Background

■ !e WWW design approach:■ Single, simple standardize interface■ Independent from storage/creation■ Trascends the complexity

■ Same design principles for application development:■ Commitment to standardization ■ Simple, generic, Content-Centric interface

Content-centric vs Control-centric interfaces

■ Content-centric interfaces principles:■ Uniform identi!ers■ Standard methods■ Extensible representation types■ Simpli!ed application integration (much less interfaces)

■ Content Repository API = Uniform interface

Content Repository

■ A Content Repository supports:■ Diverse data:

■ small & large, structured & unstructured, binary, metadata & relationships■ Services:

■ access control, locking, versioning, transactions, observation

■ "e Java Content Repository provides:■ Abstraction of data storage■ Generalized content services■ Separation of real storage from application interactions■ Standard API

■ !e JCR speci"cation de"nes an abstract model and a Java API for data storage and related services commonly used by content-oriented applications.

■ Target: any application that must handle both unstructured digital assets and structured or semi-structured information.

JCR: !e Repository Model

■ Workspaces■ Hierarchy of nodes■ Properties associated to a node■ Node types de"ne constraints(properties and child nodes)

Repository

Workspace Workspace Workspace

[root] [root] [root]

jcr:title = ‘Hello World’jcr:lastModifiedBy = ‘admin’

JSON representation of a node

http://localhost:7402/content/firststeps.infinity.json

JCR code sample

Repository repository = new TransientRepository(); Session session = repository.login(new SimpleCredentials("username", "password".toCharArray()));

// Store content Node hello = root.addNode("hello"); Node world = hello.addNode("world"); world.setProperty("message", "Hello, World!"); session.save();

// Retrieve content Node node = root.getNode("hello/world"); System.out.println(node.getPath()); System.out.println(node.getProperty("message").getString());

// Remove content root.getNode("hello").remove(); session.save();

JCR: Repository Functionalities

■ Level 1■ Login■ Read Nodes & properties■ XML export■ XPath queries■ Node types discovery■ Namespaces remapping

■ Level 2■ Write nodes & properties■ XML Import■ Assign a node types to nodes■ Change namespace registry

■ Optional■ Locking■ Transactions■ Versioning

■ SQL search■ Observation

JCR: Observation

■ Observation enables an application to receive noti"cation of persistence changes in the workspace. Base for BPM.■ NODE_ADDED■ NODE_MOVED■ NODE_REMOVED■ PROPERTY_ADDED■ PROPERTY_REMOVED■ PROPERTY_CHANGED

■ Can be asynchronous or journaled

JCR: Content Modelling

■ 2 use cases:

■ Structured content (e.g. !le storage)■ Needs de"nition of content models;■ Needs a stable structure;■ nt:resource

■ Unstructured content■ Any properties and child nodes allowed■ nt:unstructured

[nt:resource] > mix:mimeType, mix:lastModifiedprimaryitem jcr:data- jcr:data (BINARY) mandatory

JCR: node types & mixin types

■ prede"ned node types:■ nt:unstructured■ nt:"le■ nt:folder■ nt:resource represents the actual content of a "le.■ nt:version

■ mixin types provide extra characteristics to the node:■ mix:versionable: allows a node to support versioning■ mix:lockable: enables locking capabilities■ mix:referenceable: provides an auto-created jcr:uuid property

JCR Ecosystem

■ Open Standard■ Java Community Process (h"p://jcp.org)

■ Sustainability■ Reference Implementation & TCK

■ Apache infrastructure■ license, workspace, information

■ Community■ open review, testing & collaboration

■ Open adoption

■ OSGI-based scriptable application layer on top of JCR

■ REST based web framework■ Content-driven, using a JCR content repository■ Powered by OSGi■ Scripting inside, multiple languages (JSP, server-side javascript, Scala, etc.)■ Apache Open Source project

!e Sling style

■ If you happen to hear this sentence:■ “Sling is not a web applications framework, it’s a web framework.”

■ It means:■ Sling is built in a way that embraces the web.■ Sling design is based on the principles of the WWW.■ Sling processes HTTP requests in a RESTful way.

CRX Architecture

OSGI framework (felix)

JCR repository (jackrabbit)

JCR api

Application framework (sling)

‣ manages bundles as app components‣ provides system services to bundles

‣ stores the content

‣ processes HTTP requests in a RESTful way

specification implementation

architectural style

Sling Architecture

jackrabbitJCR api

standardservlets

custom servletsand components

resourceresolution

servlet/scriptresolution

JSR 223scripting

javascript

WedDAVserver

sling OSGIconsole

Sling examples using cURL

■ Create a node■ curl -F"sling:resourceType=foo/bar" -F"title=some title" h"p://admin:admin@localhost:7402/content/mynode

■ Create a node (auto-named)■ curl -X POST "h"p://admin:admin@localhost:7402/content/blog"■ curl -D - -F"title=Adventures with Sling" "h"p://admin:admin@localhost:7402/content/blog/*"

Sling URL decomposition

/geometrixx/en/products/triangle.html

/geometrixx/en/products/triangle.teaser.html

de#nes the resource de#nes the rendition

Sling URL decomposition

/geometrixx/en/products/triangle.teaser.html

sling:resourceTypegeometrixx/components/contentpage

Where to go from here

■ JSR 283 spec: h#p://jcp.org/en/jsr/detail?id=283■ Apache Jackrabbit: h#p://jackrabbit.apache.org/■ Apache Sling: h#p://sling.apache.org/

■ First steps with CRX:■ h#p://dev.day.com/docs/en/crx/current/ge#ing_started/"rst_steps_with_crx.html

JCR and Sling Quick Dive

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