Chapter 11 JavaBeans

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Chapter 11JavaBeans
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Process Phases Discussed in This Chapter
Requirements Analysis
Design
Architecture
Framework
Detailed Design
Implementation
Key
secondary emphasis
main emphasis
x
x
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Learning Goals for This Chapter
Understand

• what JavaBeans (Beans) are
• the life-cycle of a Bean
• Bean containers
• create JavaBeans
• connect Beans in BeanBox
• create applications that use Beans

Be able to
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Java Beans Design Goals 1

• Create a component technology within Java
• capitalize on Java portability
• Include GUI components
• but not limited to GUI (e.g. server bean)
• Compete with other visual programming and
  component systems
• (which are often specific to an O.S.)
• usually Windows
• require installation of some kind

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Beans Design Goals 2

• Light weight for Internet applications
• Secure
• use Java security model
• Easy efficient to distribute
• Provide mechanism which enables development
  environment (container) to determine methods,
  properties events

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permission.
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Design Goal At Work ? Reusability ?
Facilitate the easy reuse of Java code.
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Output Of Chair Maker Estimator
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Bean Phases
Phase 1. Create Bean Classes Source subject to
rules
Design / implementation time.
Phase 2. Create Bean from Multiple Bean
Classes Combine Bean classes to make new Beans
create manifest compile
Instance creation time.
Phase 3. Create Bean Instance Instantiate
object(s), usually in a Bean environment
(container)
--------
Phase 4a. Combine Beans in Bean Container to Make
Application Combine with other Beans to produce
application
Assembly time.
- or -
Deployment time.
Phase 4b. Deploy Bean and Use in
Applications Place application, Beans and
required software on target platform
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Key Concept ? Ways to use Beans ?
-- within environments connected to other Beans
within applications.
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Amenities Afforded by Bean Environments

• Detection of the Beans properties
• Read only or-
• Writeable
• Detection of listeners supported
• So events on the Bean can be handled
• Ability to easily create instances
• and display an image if an awt or swing object
• Set property values visually
• Ability to store instances

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Required Bean Rules 1 of 2

• Java source consists of Java classes
• -containing null constructor
• MyClass()
• - implementing Serializable interface
• - obeying standards shown below for
• accessor methods
• Listener registration
• Event classes

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Required Bean Rules2 of 2

• To have property myProp, include methods
• lttypegt getMyProp() // to access myProp
• void setMyProp( lttypegt p ) // to change
• For boolean property
• boolean isMyProp()
• Name for event classes to be XXXEvent
• extends Event
• Listeners must implement java.util.EventListener
• Name must end in Listener as in XXXListener
• added with public void addXXXListener(...)
  
• removed with public void removeXXXListener(...
  )

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JARing a Bean
jar cfm Bean0.jar manifest.txt Bean0.class
Creating a JAR file
First argument is name of the new JAR file
Second argument is name of manifest file
List all .class files to be included
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BeanBox Environment
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Adding a Bean to the BeanBox
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Bean1
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Setting Color
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Design Goal At Work ? Reusability ?
Be able to use Chairmaker Bean alone. Avoid
having it refer to any other non-API class.
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Initial Form of Properties Panel
(green in color)
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Design Goal At Work ? Reusability ?
Utilize Chairmaker with TicTock events. This
avoids compromising either Bean.
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Beginning to Use ChairMaker
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Setting ChairMaker to Add a Chair Leg
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An Output Of ChairMaker Bean
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Output Of ChairMaker Bean From Button Action
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Using a Bean in an Application Output
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Design Goal At Work ? Reusability ?
We want to associate Beans even when there is no
external event such as a mouse click.
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Property Change Event Demonstration
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Property Change Event Demonstration 2
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Bound Property Demonstration
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Key Concept ? Bound Properties ?
-- causes a Beans to react when a property in
another Bean changes value.
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Embedding Beans in JSP
ltjspuseBean id"object name"
1 scope"pagerequestsessionapplication"
2 class"fully qualified classname" 3 lt/
jspuseBean gt 1 Bean instance name as in
MyClass myName . 2 // Choose one when
instance is destroyed optional default is
page 3 // e.g., a.b.MyClass
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Scope of a Bean in a JSP

• page - new object created and destroyed for
  every page view.
• request - the newly created object created and
  bound to the request object.
• session - the newly created object bound to the
  session object. -- every visitor coming to the
  site will have a separate session for it, so you
  will not have to create a new object every time
  for it -- can retrieve that object later again
  from the session object when wanted
• application - object will stay as long as the
  application remains loaded. E.g., you want to
  count page views or daily sessions for your site.

Source http//stardeveloper.com8080/articles/072
001-1.shtml
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Setting and Getting a Bean Property in a
JSPIntroduction
ltjspsetProperty nameaccount17"
propertybal" value3211 /gt ltjspgetProper
ty nameaccount17" propertybal" /gt
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Summary of This Chapter

• A Java Bean is a compiled collection of Java
  classes and required files
• JARd to reduce to a single file
• Beans are used at various phases, often in a Bean
  container
• Creating from scratch
• Creating instances of
• Connecting
• Deploying as part of an application

Adapted from Software Design From Programming to
Architecture by Eric J. Braude (Wiley 2003), with
permission.
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Adapted from Software Design From Programming to
Architecture by Eric J. Braude (Wiley 2003), with
permission.