Development without Constraint

Chad Davis
● Java Software Engineer
● Colorado Springs Open Source Meetup
● Blackdog Software, Inc.
● Author
– Struts 2 in Action
– Sun Certified Mobile Application Developer Exam Guide
● Corporate Trainer – Struts 2
● Content Management System
● Am I a DBA?

Development without Constraint
( or Integrity? )

An Introduction to the Content Repository API for Java (JCR)

&

“RDBMS v. Object Storage” Discussion

Our Itinerary
● Introduction to the Content Repository API
for Java ( JCR )
● Development without Constraint ( or
Integrity? )
● “Is my project a match for the JCR?”

The Java Content Repository
( JCR )
● Java Specification
● JSR 170 ( 1.x )
● JSR 268 ( 2.x )
● How did this come to be a part of Java?

Jackrabbit
● Open Source (Apache Project)
● Reference Implementation
● “A content repository is a hierarchical content
store . . .”
● For “content-oriented” applications
● Anybody want to take a stab at defining “content-
oriented”?

Content?
● Blame the Web
● Blame the Scope Creep of IT
● Documents
● Binaries / Digital Assets
● Unpredictable Structure
● Meta-data

Bells and Whistles
● Version Control
● Full Text Search
● Observation (Event Handling)
● Unstructured / Structured Content
● Transactions
● Workspaces
● And more . . .

Data Model
● Hierarchical
● Unstructured
● Or Structured

Hierarchical Data is Natural
● File Systems
● XML
● DNS
● DOM
● Biology
● Taxonomy

The Hierachy
● Full Paths are ID's
● Hiearchy is Semantic

● Fast Navigation/Location

● Human Readable

JCR Node Trees
● Nodes
● Properties
● Values
● Names
● Structure

Property Types
STRING
●

URI
●

BOOLEAN
●

LONG
●

DOUBLE
●

DECIMAL
●

BINARY
●

DATE
●

NAME, PATH
●

WEAKREFERENCE, REFERENCE
●

More Property Stuff
● Multi-Valued
● Value Constraints

Structural Constraints: Nodes
● Node Types
– Primary
– Mixin
● Child Nodes
– Name and Type
● Properties
– Name and Type
● Inheritance

Compact Namespace & Node
Type Definition (CND)
<cd = 'http://chaddavis.com'>
[cd:contact] > nt:unstructured
cd:email ( string ) multiple
cd:pic ( binary ) mandatory

Referential Integrity
● Contained in Structure
● Use Properties
● REFERENCE
● WEAKREFERENCE
● paths/UUID

API Tour: Reading
● Direct Access
bobNode=session.getNode(“/contacts/personal/Bob Smith” );

bobEmail = session.getProperty(“/contacts/personal/Bob
Smith/email”);

● Retrieve by ID
bobNode = session.getNodeByIdentifier(bobUUID);

● By Relative Path
bobNode = personalNode.getNode(“Bob Smith”);

emailProperty = bobNode.getProperty(“email”);

● Reading Values
emailValue = emailProperty.getValue();

emailValue.getString();

inputStream = picValue.getBinary().getStream();

API Tour: Navigation
● Iterator Over Child Nodes
NodeIterator personalContactsItty = personal.getNodes();

● Iterator Over Properties
PropertyIterator propItty = bobNode.getProperties;

API Tour: Creating
● Create Node and Properties
chadNode = personalContactsNode.addNode(“Chad Davis”);

chadNode.setProperty ( “email”, “chad@mail.com”);

//binaries

Binary picBinary = valueFactory.createBinary(picInputStream);

Value fileValue = valueFactory.createValue(picBinary);

contentNode.setProperty("jcr:data", fileValue);

API Tour: Query
● SQL, XPath, JQOM
● Full Text Search
xpathExp = “/contacts/personal/element(*,nt:unstructured[jcr:contains(.,'hotmail')]";

queryMng = session.getWorkspace().getQueryManager();

query = QueryMng.createQuery(xpathExp, Query.XPATH);

results = query.execute();

● All Properties and Node Names Included in Full Text Search
● Binaries Too!

API Tour: Query
● Saving Queries to Repo

query.storeAsNode(“/queries/chad/query1”);

API Tour: Version Control
● Labels
● Merge
● Check In New Version
versionMngr = session.getWorkspace().getVersionManager();

newVersion = versionManager.checkin( nodeToCommit.getPath() );

versionHist = versionMngr.getVersionHistory( nodeToCommit.getPath() );

versionHistory.addVersionLabel( newVersion.getName(), label, false );

API Tour: Version Control
● Restore to Other Version
versionMngr = session.getWorkspace().getVersionManager();

VersionHistory = versionMngr.getVersionHistory( targetNode.getPath());

targetVersion = versionHistory.getVersionByLabel(versionLabel);

versionManager.restore(targetVersion, false);

End of JCR Tour
● Jackrabbit
● Content Management Systems
● Artifact Management
● Operations Management

RDBMS v. Object Storage

“Schema-less databases and document-oriented databases are a
paradigm shift, and it provides bigger programmer challenges than
something like picking up a new language. I would liken it to the
transition from procedural to object oriented programming.”

--Scott Swigart, “How Software is Built”

The Relational Model
● Hegemonic Concept
● Mathematical
● Taught in Every DB Course
● 1970's

Edgar Frank "Ted" Codd
●
IBM
●
Invented the Relational
Model
●
"A Relational Model of Data
for Large Shared Data Banks"
●
1970
●
“Is Your DBMS Really
Relational?"
●
“Does Your DBMS Run By the
Rules?”

Goals of Relational Model
● Mathematical
– Efficiency
– Resource Friendly
– Powerful Operations
● Program-Data Independence
– More than one app can access data
– Consider file based data persistence

Goals of Relational Model
● Data Integrity
● Column Constraints
● Referential Integrity
● Normalization
– Insert, Update and Delete Anomalies
– Data redundancy
– 3NF

Structure Driven Development
● Database Design
● Upfront Concretization of Data Model
● DDL
● Tables
● Structure Comes Before Data
● Heavy Weight
● Formal

Does Your DBMS Run By the Rules?

Impedance Mismatch
● Object-Relational
– Hibernate
● Data Types
– 1970 – No Web
– 2010 – Content, Documents, Tweets
– JSON As Storage Format?
● Structure First
– Data First
– Agile Development
● Program-Data independence
– This architectural imperitive has also shifted, but I can't quite
express it . . .

New Stuff
● NoSQL
● Schemaless DB
● Object DB
● Content Repository
● Document-Oriented DB

Some Offerings
● CouchDB
● MongoDB
● Hadoop
● SimpleDB ( Amazon )

The Case for Jackrabbit
● Coy Data
– Data Driven Development
– Agile
● Naturally Hierarchical Data
● “Content” Oriented Data
● Navigation / Query
● Integrity?

The Case for RDBMS
● Interrelated Data
● Lots of Joins
● Flat Data
● Operations

References
● Database:Principles, Programming, Performance. Patrick O'Neil and
Elizabeth O'Neil.
● JCR or RDBMS: Why, When, How? Bertil Chapuis
● Interview with CouchDB's Damien Katz
● CouchDB Rap

Development without Constraint

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