Oracle ADF Architecture TV - Development - Programming Best Practices

Real World ADF Design & Architecture Principles
ADF Programming Best Practices for Architects
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15th Feb 2013 v1.0

Learning Objectives
•  At the end of this module you should be able to:
–  Avoid common mistakes when building ADF applications
–  Understand good ADF development practices
–  Identify the patterns to develop for your ADF application
Image: imagerymajestic/ FreeDigitalPhotos.net

Secret of Oracle ADF Rockstar Programmers
"You cannot buy experience, you have to earn it"
- Duncan Mills

Program Agenda
•  ADF Business Components
•  ADF Binding Layer
•  ADF Controller
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

ADF Business Components
Architecture
Application
Module
View
Object
Entity
Object
1 *
Data Model XML
Definition
View Object
Base Class
XML
Definition
Entity Object
Base Class
References References
XML
Definition
AM
Base Class
References

ADF Business Components
Use a Layer of Framework Extension Classes
EntityImpl

YourOrgEntityImpl

YourAppEntityImpl

General Considerations
•  Always create and use custom base-classes for at least
–  ApplicationModuleImpl
–  EntiyImpl
–  ViewRowImpl
–  ViewObjectImpl
•  Note that creating custom super classes for <object>Def classes are
less common
Custom Framework Extension Classes

Entity & View Object
•  Generate Java Impl files when entity objects are accessed from
Java or Groovy
•  Ensure code that accesses entity objects directly uses type safe
APIs instead of the generic framework APIs
•  Do not generate Impl classes without a need
–  Keep code base size reasonable.
–  Impl classes for the *def classes are rarely needed
When to generate Java Impl files

View Criteria
•  Not necessary to create separate VO that only differ by their
WHERE clause
•  Apply view criteria declaratively when defining view accessor and
AM data model instances
–  Use bind variables with View Criteria
–  Be aware that "Ignore Null Values" options is of bad performance
•  Avoid direct user input in ADF BC queries to protect against SQL
injection attacks
Prefer One View Object with Many View Criteria

View Criteria
Selectively Required Option
•  Prevent user from doing
"blind" query
•  Typically includes your
indexed columns

General Considerations
•  Passivation occurs when the application module used by a user is
passed on to another user request
•  Keep in mind that
–  AM should be tuned to not passivate too often
–  Java objects are not passivated
•  Consider the use of transient attributes and mark them for passivation
•  Alternative option: Use UserData Map in ADF BC to save information you need
for longer
Think Passivation

Program Agenda
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

Understanding ADF Bindings
How Oracle ADF binds into JSF
Business Service ADF Data Binding
Web Service
POJO
ADF BC
EJB
JMX
TopLink
BAM
UI Renderer
Component
FacesCtrl
Binding
Expression Language
JSF Page
Data
Control
Data
Binding
ADF Faces Component
Tag (<af:name../>)
Server Side JSF Component
Component Model
JUCtrl Generic
Binding

Programming Against the Binding Layer
•  Expression Language
–  Current binding layer can be accessed from #{bindings}
–  Use from JSF components
–  Use from PageDef file
•  Java
–  ADF binding layer is represented by Java objects at runtime
–  BindingContext.getCurrent()is the generic entry point
–  Binding can be accessed from UI components (for example:
af:tree -> ((CollectionModel) getValue()).getWrappedData()

Understanding ADF Binding Programming
Example: Accessing the Binding Layer
import oracle.adf.model.BindingContext;
import oracle.binding.BindingContainer;
…
BindingContext bctx = BindingContext.getCurrent();
BindingContainer bindings = null;
bindings = bctx.getCurrentBindingsEntry();

Example: Accessing Attribute Binding
AttributeBinding attributeBinding = null;
attributeBinding =
(attributeBinding)bindings.get("AttributeName");
/* set / get value */
attributeBinding.setInputValue(value);
attributeBinding.getInputValue();

Example: Method and Action Bindings
//get method or action binding
OperationBinding methodBinding =
(OperationBinding)bindings.get("methodOrActionBinding");
//optional: if method expects arguments
Map paramsMap = methodBinding.getParamsMap();
paramsMap.put("argumentName1",value);
Object result = methodBinding.execute();
//check for errors, e.g. exceptions
List errors = method.getErrors();
If(!errors.isEmpty()){ …}

Example: Access Current Iterator Row
DCIteratorBinding dcIterBinding =
(DCIteratorBinding)bindings.get("IteratorName");
Row rw = dcIterBinding.getCurrentRow();
//optional: read attribute value
Object attributeValue = rw.getAttribute("AttributeName");

Typical Programming Mistakes
•  Accessing the binding context from #{data}
–  Legacy code
•  Accessing the binding layer outside of JSF and ADF request cycle
–  Filter in web.xml -> too early in the request cycle
–  Task flow initializer / finalizer -> no associated PageDef file
–  PhaseListener -> before RESTORE_VIEW causes NPE
•  "Pinning" binding reference
–  Saving bindings in a property of a managed bean that is in a scope
longer than request
–  Managed bean outlives binding container refresh cycle -> stale data

•  Attempt to access binding that is out of scope
–  Bounded task flow in region cannot access binding container of parent view
•  Call BindingContext.getCurrent() to access ApplicationModule (AM
Impl) to call method on it
–  Bypasses binding layer
–  Bypasses ADF error handling
•  Release binding container
–  ADF framework handles binding container and iterator lifecycle. No need to
explicitly release a binding
–  Cause: Legacy ADF BC coding rules
•  Fighting the framework

22 Copyright © 2013, Oracle and/or its affiliates. All rights reserved.22 Copyright © 2011, Oracle and/or its affiliates. All rights reserved.
Don't fight the framework.
Image: Ambro/ FreeDigitalPhotos.net

Program Agenda
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

Task Flow Oriented Design
•  Think task flow from design time on
•  Think "unit-of-work" and factor task flow functionality into subflows
–  Share Data Control frame with sub-flows
–  Hide sub-flows from showing in ADF library
–  If you cannot fully explain and describe a task flow in 60 seconds it
probably is too big

Use Task Flow as a "Common Language"
•  Use task flow diagrammer as "common language"
–  Use task flow templates as blue prints
–  Use verbs and meaningful names in control flow case names
•  editOrder, createOrder, manageEmployee
•  Use the display and description properties of the contained
activities to explain the non-obvious

Task Flow Design
•  Small task flows:
–  Require a lot of calling and maintenance management overhead
–  Reasonable sizes for distributed team development
–  Provide ultimate flexibility in architecture
•  Large task flows:
–  Require less calls and maintenance management overhead
–  Less flexible as you can't call discrete functionality within the flow
–  Memory footprint likely bigger than small task flows
Task Flow Sizing Considerations

Task Flow Design
•  Meet in the Middle
–  Larger task flows built out of several smaller task flows
–  Only top level task flow exposed for reuse
–  Encapsulates task flow dependencies
• Good for distributing work among developers
• Dependency management "by agreement" in smaller teams
• Smaller memory foot print through load-on-demand and task flow
private memory scopes

Task Flow Design
•  If you save a lot of data in pageFlowScope, keep the task flow small
and exit at earliest opportunity
•  Keep task flows that run in their own transaction as small as
possible and exit them at earliest opportunity

Best Practices at a Glance
•  Use input parameters and return values as the only API
•  Document task flows with diagrammer notes
•  Save task flow input parameter values in managed beans in
pageFlowScope
–  Easy to document
–  Type safe API
–  EL accessible
–  Easy to discover and manipulate task flow input values
•  Always use the smallest possible scope for managed beans
•  Don't reference managed beans in session or application scope

•  Use shared data control scope as often as possible
–  Less database connections
–  Automatic parent view collection to child task flow detail collection
synchronization
•  Define an exception handler activity in every bounded task flow
•  Make use of Task Flow Templates
–  e.g. to define exception handlers for all bounded task flows

•  Avoid cluttering diagrams for common navigation rules
•  Use wild card navigation for common functionality
–  Cancel
–  Commit
Wildcard Navigation

•  Trying to access parent view managed bean objects or bindings
–  Use object references in task flow input parameters instead
•  Use managed bean in session scope to share data
–  Consider shared data control or input parameters instead
•  Use managed bean in request or backing bean scope for bean that
switches task flows in dynamic regions
–  Use at least view scope to avoid ADF binding conflicts

•  Use of NavigationHandler().handleNavigation() to
navigate in bounded task flows
–  Queue action on hidden command button
–  queueActionEventInRegion on af:region

Managed Beans
•  Encapsulate all model manipulation code in custom AM and/or VO
methods & invoke them declaratively
–  Makes your app easier to regression test
•  Only code that belongs in a JSF managed bean is…
–  Complex, dynamic UI component manipulation
–  Complex conditional navigation
•  Even if you require backing bean code, invoke custom AM or VO
methods using action binding
–  Guarantees uniform error handling

Managed Beans
•  Managed beans are lifecycle objects that are managed
by the JavaServer Faces framework.
•  Managed beans can extend a base class
–  Super class can provide common functionality as public methods
• e.g. ValueExpression, MethodExpression utility methods
–  Comparable to JSFUtil and ADFUtil but EL accessible
• Utility classes are typically static classes
•  Recommendation: consider managed beans base
classes
Base Classes

Managed Beans
•  Backing beans are managed beans with a tight association to a view
–  Contains UI component references
–  Usually not used with more than a single view
–  Must be in request or backing bean scope
•  Backing beans are Java objects and as such
–  Increase the application code base to maintain, migrate and further
develop
•  Recommendation
–  Create backing beans only when the use case requires it
Backing Bean

Program Agenda
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

Working with managed beans is simple.
However, doing it wrong gets you into
trouble.
Here's an example.

UI Manager Pattern
•  Problem #1 – JSF component serialization exception
–  JSF components are not serializable.
–  Any attempt to bind JSF components to a bean in a scope broader
than request fails with an exception thrown
•  Problem #2 – JSF component values are not persisted in
managed bean
–  Persisting component value states in managed beans requires
scopes broader than request
–  Values in request scope reset after each request leading to loss of
user data entry and failed value change listener invocations
Two Managed Bean Problems – One Cause

UI Manager Pattern
Two Managed Bean Problems – One Solution
View Managed Bean
Request Scope
component
binding
Value 1
Value 2
Value 3
Value 4
Value 5
Managed Bean
View Scope
value
binding
ValueExpression
Lookup

•  HTML and JavaServer Faces are different technologies
–  Markup oriented vs. component oriented
–  Compile – Render, vs. multi stop request lifecycle
•  Facelets in JSF 2.x support mixing of HTML and JavaServer Faces
components
–  Prior to Facelets and JSF 2.x, mixing HTML and JSF is a no-go
–  Still with JSF 2.0 problems may occur because ADF Faces components come
with their own sizing behavior (geometry management)
–  Adding HTML to the body of a JSF or ADF Faces component may break
component functionality
•  Recommendation: Build pages and views with ADF Faces components
Mixing HTML and JSF components

•  inlineStyle property allows developers to add CSS to a component
rendering
–  CSS is applied to top-level DOM component
–  CSS is directly added to the page output
–  Recommendation: Use ADF Faces skinning and reduce the use of CSS
to the absolute minimum (e.g. conditional color coding)
•  contentStyle property allows developers to add CSS to the value
content area of an ADF Faces component
–  Styles component content area better than inlineStyle but has same
issued as mentioned above
Use of inlineStyle and contentStyle CSS

•  ADF PageDef file is not aware of ui:include or jsp:include references
in a view
–  Included fragments fail at runtime if they use ADF bound components
–  You can copy ADF bindings used by the included content into the view's
PageDef file.
•  Prevents reuse of the fragments
•  Recommendation
–  Use ui:include and jps:include for layouts only (if at all)
–  Use ADF regions to add ADF bound content to a page at runtime
ui:include and jsp:include

Program Agenda
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

JavaScript in ADF Faces is a fair option
to use. Here are the rules
1.  Know what you do and why you do it
2.  Understand the ADF Faces client
side JavaScript framework
3.  Use JavaScript by exception

ADF Faces Client JavaScript Architecture
Label1
Label2
Label3
DOM
Peer Objects
Document
UI Components
Servlet
JSF
Lifecycle
Component Tree
View Root
Form
Renderer
OK
Form
Form
UI Components
Server SideClient Side

•  JavaScript component API
•  af:clientListener
–  Listens to DOM and ADF Faces component events
•  af:serverListener
–  XMLHttp JavaScript call to server
–  Queued as custom event on client
–  Answered by managed bean
•  ExtendedRenderKitService
–  Trinidad class to invoke JavaScript from Java
Features

•  Component oriented API
•  Integrated with JavaServer Faces and ADF Faces request lifecycle
•  Ensures JavaScript calls to work on all ADF Faces certified
browsers
•  Ability to listen to component events like query, selection, popup
launch etc.
•  Allows you to suppress component events from propagating to the
server
•  Easier to learn and deal with than vanilla JavaScript programming
Benefits

Typical JavaScript Programmer Mistakes
•  Access the browser DOM tree when coding with JavaScript in ADF
Faces
–  DOM tree does work against generated HTML and not against
components
•  Use or manipulate objects ending with "Peer"
–  Use ADF Faces public APIs only: AdfRich<component name>
•  Use of methods that are all upper case or camel case with a
uppercase first letter
–  These methods are for internal use only
•  Use of objects in JS packages that have the name "internal" in them

Typical JavaScript Programmer Mistakes
•  Think that using JavaScript saves you a round trip
–  JSF to work properly requires the server side component state to
be synchronized with the client
–  Suppress server round trips only if no component state has been
changed on the client

Program Agenda
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

Secret of Oracle ADF Rockstar Programmers
Write once reuse anywhere

Problems Addressed Through Reuse
•  Duplicate code lines
–  Time spent in development
–  Inconsistent implementation
–  Increase of error surface
–  Hard to manage and change
•  Development skills
–  More people to skill on various technologies
–  Difficult to implement "expert culture”

What to Reuse ?
•  Solutions
–  Bounded task flows
•  Simplifications
–  Custom ADF frameworks that hide complexity from the
application developer
–  Example:
• PL/SQL integration framework
• Use of contextual events
• Specific page and page fragment layouts

Reusability in ADF
•  Instead of writing Java code tailored to a particular need, consider
the possibility of generalizing the code, pushing it up to a custom
framework class, allowing declarative customization of specific
cases
•  Extra up-front investment
–  Generic code is harder to write than code for a point solution
–  Use Custom properties in ADF BC
–  Use Managed Properties for Managed Beans
–  Use helper classes (utilities)
The Methodology

Don't Worship Reuse For The Sake Of It
•  Reuse should not be an infinite ideal - be practical
•  Think of “dependency firewalls” to partition solutions
•  Create dependencies in a defined and controlled environment
•  Independent components should not be impacted by changes to
siblings

Flogging a Dead Horse
•  It can be hard to tune the business’s
mindset to software reuse
–  Users/analysts won’t respect that a
BTF/component used in different
screens can’t be different
•  Revisit your architecture to see if
something initially defined as reusable
just isn’t practical
Image: msuicdragon / photobucket

Program Agenda
•  ADF Faces
•  JavaScript
•  WORA
•  Use Pattern

Surprise, Surprise !
Look mum, wheels!
They exist.

Use Pattern: Summary
•  Patterns are popular
–  Blueprint of a solution to a problem
•  Good practices
–  Identify pattern for your application
•  Layout, Functionality, Navigation etc.
–  Look at existing patterns that exist for Java EE, Mobile, Layout and
Usability
•  Very good practices
–  Don't reinvent the wheel

Conclusion
•  Gain experience
•  Learn from other people
–  OTN JDeveloper forum
•  http://forums.oracle.com/forums/forum.jspa?forumID=83
–  ADF Enterprise Methodology Group (EMG)
•  https://groups.google.com/forum/?fromgroups#!forum/adf-methodology
•  Read blogs
–  https://pinboard.in/u:OracleADF/
•  Blog your experience

Further Reading
•  ADF Architecture Square
–  http://www.oracle.com/technetwork/developer-tools/adf/learnmore/
adfarchitect-1639592.html
•  Oracle ADF Functional Patterns and Best Practices
–  http://www.oracle.com/technetwork/developer-tools/adf/index-100668.html
•  Whitepaper: An Introduction to ADF Best Practices
–  http://www.oracle.com/technetwork/developer-tools/jdev/introduction-best-
practices-131743.pdf
•  Book: Oracle ADF Real World Developer's Guide
–  http://www.packtpub.com/oracle-application-development-framework-real-world-developers-
guide/book

Oracle ADF Architecture TV - Development - Programming Best Practices

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