GCA XML Dev XML Lessons learned

1
GCA XML DevXML Lessons learned

• David Orchard
• Technical Architect
• Pacific Development Centre

2
Introduction

• Pacific Development Centre
• New Lab in Vancouver Canada
• Solutions/FOAK assets
• Education, Government, Sports, Telecom, Banking
• Technical architect on
• IBM Student Server
• University student self-service web Asset
• Access to all silo-based functions
• registration, tuition, admission, grades,
• Prototype May 98
• Ver 1.0 Asset shipped Oct 98
• Ver 2.0 Live at University of Minnesota
• One of first IBM web sites/app using XML

3
Some modest Requirements

• PeopleSoft Student Admin 7.0
• Running on Sun E10000 box
• Oracle
• has gt5000 tables
• Access by PS GUI and our app
• Integrate with Universitys X.500
• Performance
• 100 concurrent threads/requests
• hundreds of requests/second.
• Peak registration week has 60 registrations/minute
  
• Updates through Win32 based api
• registration actually done by 30 second COBOL
  job!
• Reads through ODBC

4
Solution architecture

• Web App front end on IBM 3 node 16 cpu SP2
• IBM WebSphere 2.0 Standard
• WebSphere performance pack for load-balancing
• 24 Windows NT boxes for PS API
• Connect via RMI
• Developed using Visual Age, FrontPage
• IBM Java 1.6 VM, XML4J Parser

5
Design Decisions

• Decided on XML in Nov 97
• EJB Style persistence
• No Containers or transactions
• Servlets then JSPs
• PS DB Connector
• Roles-based UI

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Declarative/XML usages

• 1. Runtime generation of HTML from Java (XML)
• 2. Compile-time generation of Java (XML)
• 3. Runtime specification of Java Objects and
  Templates (.SHTML)
• Rejected as transfer over HTTP between nodes
• RMI used
• Note All 3 forms use Java at run-time, NO
  run-time XML

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Runtime Java-gtHTML

• Via XMLXSL
• Java object-gtXML, XSL-gtHTML
• Wrote Java code to convert Java to XML using DOM
• Thrown out due to XSL tech performance
  difficulties
• Via HTML Template
• IBM internal template programming language (TPL)
• Applies XML template to Java Object
• Produces any textual output
• Java object XML-based HTML template -gt HTML
• Note Java Server Pages (JSP) can do first 2
• JSP not available at the time ( Last year )
• I still like TPL better
• Note 2 JSP/XSL different architectures

8
IBM Template Processing Language

• lttemplategt
• The business object description is
  description
• ltscope PROPERTY"career"gt
• The career code is code
• lttablegt
• ltrepeat PROPERTYARRAY"terms"gt
• lttrgt
• lttdgtcodelt/tdgt
• lttdgtdescriptionlt/tdgt
• lt/trgt
• lt/repeatgt
• lt/tablegt
• lt/scopegt
• lt/templategt

9
EJB-ish object defn. (YAEJBML)

• Data Object definition, EJB Template (XML)
• TPL based
• Generates Home, Key, Interface, Data Object,
  Business Object
• Our EJB-ish beans dont have containers or
  descriptors

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YAEJBML sample

• lt?xml version"1.0"?gt
• lt!DOCTYPE DOlist SYSTEM "../../DTD/DO.dtd"gt
• ltDOlistgt
• ltDO name"StudentEnrollment"
  package"com.ibm.studentserver.enroll"gt
• ltproperty name"emplid" key"true"/gt
• ltproperty name"classNumber" key"true"/gt
• ltproperty name"enrollStatus" /gt
• lt/DOgt
• lt/DOlistgt

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XML Views

• Used Lazy initialization of relationships
• Performance was awful!
• Created SQL Views with matching XML Views
• Binds SQL Views to YAEJBML elements
• New findBy method on Home
• follows view specification
• Some restrictions
• Result Set Columns must be grouped by Bean
• No circular references

12
Declarative Non-XML usage

• Created Web Object Builder (WOB)
• Parameters to WOB Servlet
• Business Object, Keys, FindBy Method, Template
• ltSERVLET NAME"WebObjectBuilder"
  CODE"com.ibm.whistler.WebObjectBuilder"gt
• ltPARAM NAME"TEMPLATE" VALUE"com.ibm.whistler.stu
  dentserver.currentenrollment.CourseInformation_Cur
  rentEnrollmentsViewImpl"gt
• ltPARAM NAME"BUSINESS_OBJECT" VALUE"com.ibm.whist
  ler.studentserver.currentenrollment.CurrentEnrollm
  entsView"gt
• ltPARAM NAME"HOME_METHOD" VALUE"findBy"gt
• ltPARAM NAME"KEY" VALUE"EMPL_ID"gt
• ltPARAM NAME"KEY" VALUE"INSTITUTION"gt
• lt/SERVLETgt

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Declarative mechanism for

• BO Home.findByMethod(Keys from POST or session
  data )
• Lock web session
• set web session on BO
• execute method specified or commit()
• render according to template
• get web session data from BO
• put into web session
• unlock web session

14
Declarative everywhere

• PeopleSoft or RDB binding to Java class (DO) in
  XML
• Views binding in XML
• Template for Java object to HTML in XML
• Originally XSL then IBM template tool
• HTML/JSP page specifying Java Object and Template
  to render
• VIP Everything can be declarative
• Assumes no behavior in Java Object
• But can add behavior betwixt presentation and DO

15
ve Design lessons

• Declarative means reuse at design/compile time!
• View optimizer would have been much harder if EJB
  code
• Declarative means easily regenerate code
• Not as many options for tracing/logging/debugging
• Much easier to create hundreds of DOs than VAJ
• Complete control over behavior and interface
• Declarative means easy to adapt
• IMHO, adaptability is a crucial success factor
• refactoring classes meant text search and replace
• GUI developers didnt need VAJ
• Declarative means easy to author
• Data Objects, Object templates, Web templates

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-ve Lessons Learned

• Myths
• XML will replace Java programming
• XML always means presentation independence
• Java DOM are sufficient/perfect together
• XSL is easy and will become ubiquitous
• Model Data correctly for interchange
• Observations about XML and Transforms

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Myth Procedures in XML

• Tried in 2 places
• HTML Template
• DO templates
• End up creating declarative constructs for
• parameters, data types, expressions, loop
  constructs, variable scoping, subclassing/extensio
  n
• Can became convoluted
• TPL, XSL suffers from this
• Cant author/debug like Java
• Suggestion Declarative for pattern matching
• sed/awk/perl/xsl
• Better Java text templating would have solved
  problem

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Myth Presentation Independence

• Soo many RFPs with the XMLXSL to any client
• Especially XML to IVR Palmtop browser other
  business
• Works in many cases, usually document focused
• Similar styles of documentation - print web
  pages
• Rebranding of content - stories to branded web
  sites
• Interactive web sites are a different story
• Many issues from XML to client
• Navigation, Input Data validation, Output
  Formatting, Amount/ordering of content, Scrolling
  in content
• Process becomes multi-step
• Dispatcher queries for content, then format
• Suggestion XML best chance at re-use

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Myth Java/XML perfect together

• Common B2B, B2C Use Case
• Take lots of EJBs and convert to XML
• Condition read-only classes and DTDs
• Either
• Write procedural code using DOM to serialize
• Use reflection-based Conversion
• Usually use DOM
• Poor performance in current implementations
• Transfer strongly typed XML tree to Java tree
• ie public class student -gt ltstudentgtlt/studentgt

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XML/Java issues

• Inheritance
• Java has, XML doesnt
• Contain/embed/link to the parent?
• Implements, extends?
• References
• Java has handles, XML has Linkss
• Typing
• Java primitives to strings and back
• Built-in types Java classes
• Array/Vector/List/Hashtable become ??
• String value become attribute or entity
• XML Pis and Comments

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Java/XML ideas

• Serialization Proposal
• XML binding for Javalt--gtXML aka YAEJBML
• NOT the focus of the Sun Java/XML data binding
  JSR
• Compile XSLT to Java for performance
• Perl/SAX pattern/entity matching in Java
• Interface between XSLT and Java
• call XSLT from JSP
• call Java from XSLT
• BUT still problems of type conversion
• Java based template string and streams
• MessageFormat is awful, poor child of sprintf
• generalization of JSP
• Perl, others have
• IMHO, only perfect because java xml parsers

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Myth XSLT solves presentation

• XSLT is declarative programming language
• XSL has all the constructs of a programming
  language
• Procedures, parameters, variables, VM (DOM)
• Difficult to author and debug
• ie, creating a Form with CSS, JavaScript, nested
  tables
• Course list table with radio buttons select
  course and required subcomponents
• XSLT needs usability performance/scalability
  improvements
• Serialize Java tree into DOM tree currently
• Solution Know when to use XSL vs JSP

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Myth Model Data Correctly

• Same Universal Model myth heard with rdb and
  Java
• Same modeling problems exist in XML
• Example When is a person a student?
• Finance dept When fees charged
• RegistrarAccepted to University
• Department Enrolled in any course
• Instructor Enrolled in course with grade
• Student society Paid student fee
• Do you create a student entity?
• Solution Dont be deluded into correct model
  thinking

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Observations

• XML everywhere means transforms are key
• Need to chain multiple transforms together
• Different sources/sinks of transform data
• Transforms are behavior
• Death of O-O?
• Where does Java fit?
• Watch for much confusion in market on
• JSP EJB on DB versus XSLTXML on DB

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XML Schema Announcement

• Preview of new XML4J functionality
• binary only, 90 day license, to be updated
  frequently
• feedback to XML4J_at_us.ibm.com
• Supports subset of 6 May 1999 Schema Working
  Draft
• subset corresponds to DTD functionality - no
  datatypes
• track the whole Schema spec
• read and validate documents using either DTDs or
  schemas
• convert DTDs to schemas and schemas to DTDs
• access to DTD and Schema via a DOM extension

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Summary

• XML widely usable for defining Data
• Debatable use for defining behavior/procedures
• Combined with code generation
• Adaptable software
• Easy to author
• End2End functionality without Java
• Can be part of large performance scalability
  systems
• Student Server
• Proven Universal Data Language
• Needs work, watch out for hype
• tooling, maturity, Java integration
• Pretty Good for a toddler!