JCR in Action. Content-based Applications with Apache Jackrabbit. Carsten Ziegeler.

Transcription

1 JCR in Action Content-based Applications with Apache Jackrabbit Carsten Ziegeler Apache Con US Presentation November Oakland

2 About Member of the ASF Sling, Felix, Cocoon, Portals, Sanselan, Excalibur, Incubator PMC: Felix, Portals, Sling, Incubator, Excalibur (Chair) RnD Team at Day Software Article/Book Author, Technical Reviewer JSR 286 Spec Group (Portlet API 2.0) 2

3 Motivation Tried and trusted NOSQL solution Standard Java API First spec released in May 2005 Open Source Implementation 1.0 Release in April 2006 Think about your data storage use cases JCR might help 3

4 Agenda JCR and Apache Jackrabbit Basic Content Modeling References and Search Advanced Features Demo: Sample Application Summary and Questions 4

5 Content Repository 5

6 Content Storage Hierarchical content Nodes and properties Structured Nodetypes and typed properties And/or unstructured Fine and coarse-grained 6

7 Sample Application Digital Asset Management Hierarchical storage of pictures Upload Tagging Searching Automatic thumbnail generation Poor man's flickr... 7

8 Sample Content Structure Travel Family Europe Weddings Amsterdam Basel City Photo Photo Photo Photo 8

9 Sample Application Java web application Uses Apache Sling as web framework Content repository managed by Apache Jackrabbit Interaction through the JCR API 9

10 JSR 170: Content Repository for Java TM technology API (Java) Standard Version 1.0 Supported by many vendors Used by many products and projects Several open source solutions How do you connect to a CR? How do you interact with a CR? 10

11 JSR 283 : JCR 2.0 is final New features Improved specification Cleaned up API (deprecation) Revised specification document Binary compatible JSR 170 apps run without modification More later... 11

12 CR : Combines Advantages 12

13 Content Repository Features Query (XPath, SQL) Export/Import (XML) Referential Integrity Authentication Access Control Versioning Observation Locking and Transactions (JTA) 13

14 The Repository Model Repository: one (or more) workspaces Workspace contains a tree of items Item: Node or property Nodes provide the content structure May have children Actual data is stored as values of properties Types and namespaces! Implementation of JCR 14

15 Nodes and Properties = Node Root Workspace A Content Repository = Property a b c d e g h Once upon a time i j k true 6.02x10 23 Implementation of JCR 15

16 Connecting to the Repository JCR

17 Connecting to the Repository JCR 2.0 provides RepositoryFactory Uses Service Provider Mechanism META-INF/services/javax.jcr.RepositoryFactory Just use RepositoryFactory.getRepository(null) Or specify connection parameters RepositoryFactory.getRepository(Map) 17

18 Working with the Repository 18

19 Traverse the Hierarchy 19

20 Retrieve a Property 20

21 Interaction Summary Get the repository Login to a workspace Provides a session Use the session to Access nodes and their properties Change and save them 21

22 22 Apache Jackrabbit JSR 170 and 283 reference implementation Apache TLP since 2006 Releases 1.6 (JSR 170 based) 2.0 Beta 2 is out (nearly) 2.0 Final (end of 2009) announcesubscribe@jackrabbit.apache.org Components Commons, API RMI, WebDAV, WebApp, JCA OCM And more

23 Words of Advice Read (or browse) the JCR specification jcr-1.0.jar/jcr-2.0.jar included Getting started with Jackrabbit jackrabbit-webapp: Drop-in deployment First Hops: Embedded repository Take your time Think about your use cases Have a look at Apache Sling 23

24 Agenda JCR and Apache Jackrabbit Basic Content Modeling References and Search Advanced Features Demo: Sample Application Summary and Questions 24

25 Starting point: Leverage the standard node types Type hierarchy Content hierarchy nt:hierarchynode nt:folder nt:file nt:linkedfile nt:unstructured 25

26 Bottom-up modeling: Content types my:album > nt:folder - description (string) - date (date) my:tag - name (string) - description (string) my:photo > nt:file - description (string) - location (string) - tags (string[]) my:resource > nt:resource - width, height (long) - format (string) 26

27 Top-down modeling: Content hierarchies Travel Family Europe Weddings Amsterdam Basel City Photo Photo Photo Photo 27

28 Content Modeling: Words of advice Namespaces Use a single namespace per company or application Use a reasonably unique namespace prefix Prefixed names for structured content Default namespace for unstructured content 28

29 Content Modeling: Words of advice Use an application root node /my:content Good for searching, backup, and migration Avoid flat hierarchies User interface complexity Content-driven design Design your content before your application 29

30 Content Modeling: Words of advice Checkout Apache Jackrabbit wiki and mailing lists "Davids Model" Look at existing node types Mixin node types possible 30

31 David s Model Rule #1: Data First, Structure Later. Maybe Rule #2: Drive the content hierarchy, don t let it happen Rule #6: Files are Files are Files Look at DavidsModel 31

32 Agenda JCR and Apache Jackrabbit Basic Content Modeling References and Search Advanced Features Demo: Sample Application Summary and Questions 32

33 Alternative Views: References Tags Album Favorites Bird Tree Photo Top 10 Picks Photo link link link API: Node.getReferences():PropertyIterator Property.getNode():Node Node.setProperty(String name, Node) 33

34 Sample Alternative Views Reference by name my:photo > nt:file - description (string) - location (string) - tags (string[]) my:tag - name (string) - description (string) 34

35 Sample - Alternative Views Reference by path / my:photo > nt:file - description (string) - location (string) - tags (string[]) /Tags/bird Tags bird 35

36 Alternative Views: Search Looking for Latest photos XPath / jcr:root/my:albums//element(*,my:p hoto) [@data > xs:datetime( )] SQL SELECT * FROM my:photo WHERE jcr:path LIKE /my:albums/% AND date > DATE Favorites with keywords / jcr:root/my:albums//element(*,my:f avorite) /jcr:content[jcr:contains(., )] SELECT * FROM my:favorites WHERE jcr:path LIKE /my:albums/% AND CONTAINS(*, ) API: Session.getWorkspace().getQueryManager():QueryManager QueryManager.createQuery(String stmt, String language):query; Query.execute():QueryResult 36

37 Alternative Views: Words of advice Moderate use of references Circular references only within a subtree Plan for backup and content migration Best search performance when selecting a small subset of content References, path or name property 37

38 Agenda JCR and Apache Jackrabbit Basic Content Modeling References and Search Advanced Features Demo: Sample Application Summary and Questions 38

39 Observation Optional feature of the JCR specification Enables applications to register interest in events Monitor events Respond to events API: ObservationManager: addeventlistener(eventlistener listener, int eventtypes, java.lang.string abspath, boolean isdeep, java.lang.string[] uuid, java.lang.string[] nodetypename, boolean nolocal) Advanced JCR Features 39

40 Event Types Events can be of 5 different types Node added Node removed Property added Property removed Property changed Advanced JCR Features 40

41 Observation Events Describe changes to a workspace Dispatched on persistent change Provide the path of the item Provide the user ID Only provided to sessions with sufficient access privileges Events may not be complete! Example: removal of a tree of nodes Advanced JCR Features 41

42 Event Listeners Registered with a workspace Registration with optional filters Like node types, paths Receive events for every change API: public void onevent(eventiterator events); Advanced JCR Features 42

43 Events Advice Events occur after a save Modification based on events is a new operation Such events can be filtered Events may not tell the complete story Tree removal, copy, move Most common pattern Node added, removed, changed Advanced JCR Features 43

44 Staged Publishing: Versioning Version store Staging Live 44

45 Jackrabbit Configuration Workspace configuration XML configuration Persistence Managers Query index configuration (Lucene) File system configuration Check out the documentation 45

46 Agenda JCR and Apache Jackrabbit Basic Content Modeling References and Search Advanced Features Demo: Sample Application Summary and Questions 46

47 Getting Content Get the repository Login to a workspace Returns a session Starting with the session Navigate to the desired content Get the query manager and search 47

48 Writing Content Get the repository Login to a workspace Returns a session Navigate to the correct node To change it To add new nodes/properties To remove nodes/properties Persist changes 48

49 Advanced Development Apache Sling REST based web framework Powered by OSGi Scripting Inside Apache Jackrabbit OCM Map content to Java objects and vice versa Similar to database ORMs 49

50 JCR 2.0 Features Abstract Query Model Java Query Object Model / SQL ACL and Access Control Policies Plus Retention Policies and Hold Nodetype Registry New Property Types and Nodetypes Shareable Nodes (Graph) Journalling Observation 50

51 Agenda JCR and Apache Jackrabbit Basic Content Modeling References and Search Advanced Features Demo: Sample Application Summary and Questions 51

52 (Nearly) Everthing is Content Application Domain Specific Content Presentation Support (HTML, CSS, JavaScript, Images) Documentation, Translations... 52

53 Conclusion Content Repositories Combine advantages from FS and DB Add important features Structure/Access your data the way your domain requires it JCR The Java API Apache Jackrabbit The Implementation 53

54 Famous Last Words Read the specification JCR in your application? Join the Jackrabbit community! Seriously consider Apache Sling for web applications Check for additional stuff like OCM 54

55 Q&A 55